and that prognathism in insects to-day is a secondary condition. As Macropathus filifer exhibits a number of primitive characters it seems that Snodgrass's statement is probably more correct.

Antennae Figs. 3, 4. Situated on the inner side of and partially below the compound eyes; the long, slender, tapering, very flexible sensory flagella are four and a-half times as long as the body in both male and female (excluding ovipositor in females). The antennal sclerite (Asl) forms a ring at the base of each antenna, which is separated from the rest of the head-capsule by the antennal suture (As). The scape (S) of each antenna articulates with a lateral process on the antennal sclerite and is connected all round to the antennal sclerite by a membrane (Im). In the male (Fig. 3, A, B), the scape is greatly enlarged, about four times the size of the pedicel (P) which, although narrower and shorter than the scape, is broader than the other segments. The third segment, on the dorsal aspect, is narrower, but half as long again as the pedicel, and on the ventral aspect equals the pedicel in length. From the fourth segment onwards the segments are unequal in length, although steadily decreasing in size. Some segments are only partly divided; some have a ventral retrolateral spine (Sp) in which case the distal part of the segment is swollen and the spine is borne on this swelling; prolateral spines entirely absent. This spination of the antennae is found only in the mature male, and there is great variability in the number of spines present (Fig. 3, C); it is an example of sexual dimorphism. In the female (Fig. 4, A, B, C) the antennae are essentially the same except that the scape is not as thick as that of the male and consequently the flagellum is not as long. In both sexes the antennae are thickly clothed with setae. The long flagellum is easily broken so that the length varies, and in no cases has regeneration of lost segments been observed after an ecdysis.

Compound Eyes And Ocelli. Two pear-shaped compound eyes (Fig. 1, Ce) lie dorso-laterally to the antennae. Between the antero-medial margins of the antennal sclerites on the frons (Fig. 1, Fr) is a small white pear-shaped structure which is the only ocellus (Fig. 1, Oc) that survives in Macropathus filifer. Each eye, in which there are approximately a thousand facets, is surrounded by a chitinous ring, the ocular sclerite (Fig. 2, Osl), and where it joins the head-capsule is the ocular suture (Figs. 1, 2, Ocs). There is a small white area in the dorso-posterior region of each eye where the facets of the eye are much smaller.

Capsule Figs. 1, 2, 5 The frons (Fr) is the median sclerite lying directly anterior to the epicranium (Ep), but not separated from it by a suture. Laterally there is no fronto-genal suture to divide it off from the gena; distally it is separated from the clypeus (C) by the invaginations forming the anterior arms of the tentorium, but the greater part of the clypeus is continuous with the frons and the epistomal suture is absent. The clypeus is divided ventrally into ante-clypeus (C) and dorsally into post-clypeus (Pc) by the clypeal suture (Cf.). At the junction of the post-clypeus with the mandibular sclerite (Mns) is a concave process that articulates with the ginglymus (Gl) of the mandible The post-clypeus is brown and chitinized and the ante-clypeus is white and membranous. The cheek is formed by the gena which is separated from the mandibular sclerite by the subgenal suture (Sgs); postero-laterally it is separated from the narrow postgena (Pg) by the occipital suture (Os); dorso-laterally it is separated from the vertex (V) by another suture unlike anything found

dendritic sensory papillae (Fig. 8, Dsp); dendritic papillae are also situated near the distal margin and are probably concerned with taste. The inner surface is continuous with the inner membranous surface of the clypeus and forms the epipharynx. The inner surface of the ante-clypeus is less thickly clothed with hairs than the labrum, and is separated from it by two small chitmous bars, the tormae (Fig. 6, T).

Mandibles. Figs. 10, 11. Very strongly chitimzed; situated one on either side of and behind the labrum; strongly toothed with an apical bifid tooth (Bt) extending one-third down, a single subapical tooth (St) extending from one-third to one-half down, and a sub-basal tooth (Ct) with six cusps between one-fifth and two-thirds up. The proximal surface carries a thick clothing of setae and a blunt projection from the posterior surface. Mandibular sclerite small, continuous with the post-clypeus, separated from the gena by the invagination forming the anterior arm of the tentorium of its side, and the subgenal suture. The mandible articulates with the head-capsule by an anterior ginglymus (Gj) and a posterior condyle (Cd). The ginglymus articulates with a concave process situated at the point where the post-clypeus and mandibular sclerite are joined. The condyle articulates with an acetabulum on the ventral margin of the occiput.

Maxillae. Fig. 9. Behind the mandibles are paired maxillae which, excluding their palps (P), are slightly larger than the labium. The cardo (C) is triangular in shape, with the length to the width as 1.1:1, and articulates with the rim bordering the lateral margin of the occipital foramen. Distal to each cardo is the stipes (S), twice as long as broad and a third as long again as the cardo. Externally each stipes carries a five-segmented maxillary palp (P), which is thickly clothed with setae and very sensitive to touch and chemical senses. Each palp arises from a palpifer (Pf), formed from the outer distal portion of the stipes by constriction from the rest as a separate lobe. First two palpal segments short, last three long, of which the terminal segment is club-shaped. The relationship of the length of each segment to the palp is 7:7:20:20:44. Proximally the stipes carries a lacinia (L) and galea (G) which are both weakly chitinised. At the tip of the lacinia is a bifid spine, and beneath this spine an articulated spine. The internal surface of the lacinia has numerous long setae. The galea consists of two joints, a proximal one, the sub-galea (Sg) which is short and slightly swollen, and a distal one which is elongated and at its tip bears an area of sensory papillae (Sp) behind which is a group of setae.

Labium. Fig. 13. The submentum (Sm), mentum (M), prementum (Pm), palp (P), ligula (Lg), glossa (Gl) and paraglossa (Pgl) are all present. The submentum is large, length related to width as 1:1:2; it articulates with the rim at the anterior margin of the occipital foramen and also with the small mentum. Mentum wider than long, as 2.3:1. The prementum, which is wider than long as 1:4:1, lies in front of the mentum and is cleft anteriorly for a third of its length. Submentum mentum prementum are related in length as 2.2:1:1.5. On each side of the prementum is a palpiger (Pa) which bears a three-segmented labial palp, the ratio of the length of each segment to the total length of the palp being 21:30:50. Both palps are clothed with setae; last segment of the palp is club-shaped and more heavily clothed with setae towards its apex, where the setae form a series of whorls all directed inwards towards the apex. Anterolateral to the prementum are two small ligulae, each of which bears a large thick

The pleuron in most insects bears three inwardly directed processes for the attachment of muscles. These usually comprise a dorsal pleural wing process for articulation of the wing; a lower lateral pleural coxal process (Pcp) with which the coxa articulates; the pleural suture and pleural ridge (entopleuron) (Er) extending through it; and the pleural arm (Pa) which is situated a short distance above the coxal process, projecting inward and downward from the entopleuron to rest against the furca and thus form an internal connection between the pleuron and sternum.

Macropathus filifer being apterous lacks the pleural wing process, and in the propleura the pleural arm is missing from the entopleuron. In the three segments the epimeron is considerably reduced, while the episternum is large. The episternum is subdivided longitudinally and has a thickened ventral margin. In the prothorax only it is fused with the precoxale which passes ventrally to unite, but not fuse, with the sternum and thus form a bridge connecting the episternum to the sternum. The precoxale is absent from the mesothorax and metathorax.

Articulating with both the antero-mesal margin of the coxa and the anterior end of the thickened ventral margin of the episternum is a small, transversely placed, triangular-shaped sclerite, the trochantin (T).

Between the thoracic segments, situated within the intersegmental membrane, are the intersegmentalia, the sclerites which surround the spiracle. The third thoracic spiracle belongs to the first abdominal segment. Snodgrass (1935a) says that the first and second spiracles belong to the mesothorax and metathorax respectively, although they often “migrate forward during development and come thus to have a definitive position in the secondary intersegmental membranes or in the posterior parts of the segments preceding them. The meso-thoracic spiracles particularly are subject to this anterior migration and hence often occur in larval or adult insects on the sides of the prothorax, for which reason they are frequently called the ‘pro-thoracic’ spiracles. “In Macropathus filifer the spiracles have moved forward into the posterior part of the pro-thoracic and mesothoracic intersegmental membranes and the mesothoracic spiracle is much larger than the metathoracic one.

Sternum. Figs. 17, 18. The prosternum of Macropathus filifer is divided into four parts—prosternite (Pt), verasternite (V), fureasternite (F) and spinasternite (St). The prosternite is absent in the mesosternum and metasternum but the other three sclerites are present. Martin (1916) says the sternum of insects is “composed of five subdivisions,” but the fourth division, the post-furcasternite, is not present in M. fiilifer.

Prosternum. Anteriorly this consists of a poorly chitinized area formed from a membrane with rings of chitin embedded in it (Pt), which extends into the cervicum. Situated immediately posterior to this is the verasternite (V), which is produced at each anterior corner into a long arm directed antero-laterally. The verasternite is connected by a narrow membrane with the precoxale (Pc), which is fused to the episternum (E) forming the precoxal bridge. There is no postcoxale. The furcasternite is situated directly behind the verasternite, from which it is separated by a membrane. Anteriorly it is divided into two short processes and internally it bears the furca (Af) which consist of two long, slender, anteriorly directed arms, each terminating in a thin plate. The spina-

sternite is very small and oval and bears the single, median, star-shaped spine (Ms), consisting of five approximately equal arms.

Mesosternum. The verasternite, furcasternite and spinasternite are all fused together forming one large plate. The posterior margin bears the medifurca (Mf) and the median spina. There is no precoxale. The medifurca consists of a stalk attached to the furcasternite and bearing two laterally diverging arms, each one of which bears three processes directed anteriorly, antero-laterally and posteriorly respectively. The antero-lateral of these processes is the largest, and it articulates with the pleural arm (Pa) of the entopleuron on its side. The spina is attached by a stalk to the spinasternite and bears five arms—two large ones antero-laterally, two small ones anteriorly, and one large one posteriorly.

Metasternum. The small oval verasternite lies partly in a median depression of the furcasternite from which it is separated by a membrane. The furcasternite is large and bears two anteriorly directed arms. The spinasternite is reduced to two very small sclerites at the base of the furcasternite. The metafurca (Mtf) which is attached to the furcasternite consists of a stalk bearing two laterally diverging arms. Each arm bears three processes directed anteriorly, postero-laterally and posteriorly respectively. The postero-lateral process is the longest, and it articulates with the pleural arm of the entopleuron. Attached to the spinasternite is the median spina consisting of five arms—two long ones directed antero-laterally, two shorter ones postero-laterally, and a much shorter one posteriorly. Of the spinasternite Martin (1916) says, “It is so variable in position that it is very hard to tell to which segment the spinasternite belongs, but it probably belongs to the segment in front of it, as no spinasternite has ever been described as occurring in front of the prothoracic verasternite.” In M. filifer this is true, for the spinasternite is definitely the last sclerite of each segment. In contradiction to Snodgrass (1935a). who states: “It should be observed that the metasternum never has a spinasternite, because the third intersternite either is suppressed or becomes the acrosternite of the first abdominal sternum”, M. filifer has a small spinasternite to which is attached a well developed spina.

Cervical Sclerites. Fig. 17. There are three pairs of lateral cervical sclerites (Lc). The anterior one is oblong and in front articulates with the margin of the occipital foramen to which its anterior end is connected by a membrane. Posteriorly it articulates with the forward edge of the triangular-shaped second sclerite, and this in turn articulates with the third sclerite which is the largest of the three. This third sclerite bears a large postero-lateral arm and articulates behind with the precoxal bridge.

There are two pairs of oval shaped ventral sclerites (Vc) embedded in the membrane of the neck, the posterior pair being more strongly chitinized than the anterior pair.

Legs. Figs. 21-23. The legs are long and slender The fore and middle limbs are about the same length, but the hind limb is much longer and more powerfully constructed for jumping. Each leg consists of six articulating segments—coxa (C), trochanter (Tr), femur (F), tibia (T), tarsus (Ta) and pretarsus (Pta). Crampton (1923) states, “The trochanter articulates with the coxa but does not articulate with the femur in any insect I have examined, and it is quite possible that the trochanter may be a constricted off portion of the femur.” Maskell (1927) says, “In the metathoracic legs of Hemideina the

trochanter is firmly attached to the femur, there being no articulation between them. But in the prothoracic and mesothoracic legs there is a small but distinct articulation between trochanter and femur”. In Macropathus filifer there is a definite articulation between the trochanter and femur in all three pairs of legs. It is especially noticeable in the metathoracic legs where the articulation is easily broken and the legs lost, while the coxa and trochanter remain attached to the thorax. Auditory organs are lacking on the prothoracic tibia, and because of this there is no area of small spines on the femur of the hind leg, nor a file

Text-fig. 4. Thoracic Appendages.—Fig. 21—Left hind leg. Fig. 22—Left middle leg. Fig. 23—Left fore leg.
A, apical spine; Asp, apical spur; C, coxa; F, femur; Pl, pseudopad, but euplantula lacking; Pta, pretarsus; Sa, subapical spine; T, tibia; Ta, tarsus; Tr, trochanter; U, unguis

the superior apophysis (Figs. 28, 29, Sa), projects forward into the haemocoele from the dorsal basal region of each valvula. Both these pairs of apophyses serve for muscle attachment.

The inner valvulae roof over the passage along which the eggs are passed.

The ventral valvulae arise from the posterior margin of the eighth sternum. Each consists of a short basal segment, the basivalvula (Figs. 24, 26, 27, B), and a longer shaft The basivalvulae are distinct, though not heavily chitinized, and are not wholly concealed by the rather small subgenital plate. Between the basivalvula, the ninth tergite (Fig. 24, T. IX) and the base of the dorsal valvula is the subtriangular first valvifer (Figs. 24, 26 1Vf). Dorsal to this is the second valvifer (Figs. 24, 26, 2Vf). These valvifers form the antero-lateral part of the ninth sternum.

The broad proximal portion of the dorsal valvulae passes imperceptibly into a longer, more slender, distal portion not separated by a suture so that no basivalvulae are recognisable.

The eighth sternum is prolonged caudad as the subgenital plate covering the vulva and bases of the ventral valvulae. On the ventral surface of the subgenital plate is a flap of tissue closing the aperture of the genital chamber. The sub-genital plate (Fig. 24 Sgp), which is obtuse-angled laterally, and deeply emarginate distally, appears constant in shape in all the animals I have examined. It is thickly clothed with setae.

The supra-anal plate (Fig. 25, Sap), though well developed, is not divided transversely into two sclerites—i.e., there is no separate eleventh tergite and the plate is not sharply marked off from the tenth tergite (Fig. 25, Tx). The shape of the supra-anal plate is not constant but varies between two extremes, one of which is rounded and notched in the centre (Fig. 28, Sap), while the other is obtuse-angled laterally and truncated terminally (Fig. 25, Sap). Many intermediate stages occur, some straight, some slightly concave, and others slightly convex.

The paraprocts (Fig. 25, Pp) are well developed, but little chitmized, and are clothed with brown setae.

The long, flexible cerci (Figs. 24, 25, C) taper from a stout base to a slender apex. There is a basal segment (Fig. 25, Bc) at the base of each cercus. The cerci are clothed with long and short setae and are similar in both sexes.

Male. The supra-anal plate (Fig. 31, Sp) is well developed and fused with the tenth abdominal tergite (Tx). As in the female its shape is not constant. It may be either concave or convex terminally or of an intermediate stage between these two extremes. The ninth sternum (Fig. 30, S Ix) is undivided, and on each side disto-laterally bears a terminal stylus (Figs. 30, 31, S). The cerci (Figs. 30, 31, C), which are as already described for the female, are not modified to function as claspers.

Situated in the large membranous area between the paraprocts (Figs. 31, 32, Pp) and the ninth sternum is the penis (Fig. 32, Pn). This organ itself is almost entirely membranous and is divided into four lobes, two dorsal and two ventral. On the tips of the two upper ones are the openings of the male genital ducts (Fig. 32, Op), clearly demarcated by their chitinized margins. Arched over the base of the penis is the hood-like pseudosternite (Fig. 32, Pd) the cavity of which forms a sheath into which the penis may be retracted. It serves for the insertion of muscles concerned with the movements of the penis

anterior arm of the tentorium, one inserted on the inner face of the cardo, the other on the outer face. The adductor muscles of the stipes (As) arise on the posterior end of the anterior arm of the tentorium and are inserted on the inner side of the stipes. The muscles of the galea, lacinia and the intrinsic muscles of the palp, enable them to move independently of the whole maxilla.

Text-fig. 7. Muscular System —Fig. 34—Inner surface of terga showing dorsal muscles.—alary muscles removed. Fig. 35—Inner surface of sterna showing ventral muscles.
Abc, abductor of coxa, Adc, adductor of coxa, Ef, extensor of femur. Fm, muscle of furca, Is, inner sternal; It, inner tergal, Ld, longitudinal dorsal muscle to head, Los, lateral outer sternal; Lt, lateral thoracie, Ltg, longitudinal tergal, Mc, muscles of cercus Mos, median outer sternal, Mp, muscles of paramere, Mr, muscles of reproductive system, Ot, oblique tergal, Ps, prosternal muscle, Pt, 1st and 2nd protergal muscles to head; Sp, sterno-pleural, 1 Ts, hytergo-sternal; 2 Ts, 2ry tergo-sternal, Tsn transverse sternal, Vl, ventral longitudinal muscle to head.

The musculature of the labium is similar to that of the maxilla. Arising from the posterior tentorial arms are the proximal (Prm) and distal (Drm) retractors of the mentum. The proximals are inserted on the lateral basal angles of the mentum, and the distals on the anterior wall of the prementum at the inner basal angles of the glossae. As in Dissosteira carolina described by Snodgrass (1928), the glossae, paraglossae and palpi are all supplied with individual intrinsic muscles. Overlying the distal retractor muscle of the mentum is the retractor of the hypopharynx (Rh), which is inserted on the posterior part of the hypopharynx. The buccal region and pharynx are supplied with dorsal, ventral and lateral dilator muscles (Dp).

Thorax. The head is connected to the thorax by dorsal (Fig. 34, Ld) and ventral (Fig. 35, Vl) longitudinal muscles, the dorsal extending from the postoccipital ridge to the posterior part of the pronotum and the ventral from the

posterior arm of the tentorium to the prosternum. Also connecting the head to the thorax are the protergal (Fig. 34, Pt) and prosternal (Fig. 35, Ps) muscles extending from the postocciput to the pronotum and prosternum (Fig. 34).

In the thorax longitudinal tergal (Fig. 34, Lt), inner tergal (Fig. 34, It), and sternal (Fig. 35, Is) muscles occur in each segment and transverse sternal (Fig. 35, Tsn) muscles are present in the meso- and metathorax where they act as retractors of the thorax The principal muscles of the thorax are those concerned with movement of the legs. Since M. filifer has no wings, the powerful muscles connected with flight are absent. There are three main muscles to each leg, the adductor (Figs. 34, 35, Adc) and abductor (Figs. 34, 35, Abc) of the coxa, and the extensor of the femur (Figs. 34, 35. Ef) These arise on the sternum of their respective segment, the coxal muscles being inserted on the rim of the base of the coxa, and the femoral passing on to the femur.

Leg. Fig. 40. In addition to those muscles in the thorax concerned with the movements of the leg as a whole, there are also a number of muscles within each joint of the leg. The trochanter is operated by two muscles, the levator (Lt) and depressor (Dt) of the trochanter, arising on the base of the coxa and in serted on the rim of the trochanter. In the femur the posterior levator of the tibia (Plt) occupies most of the cavity of the femur. The fibres of this muscle extend into the dorsal crest of the femur, while distally they taper to a thick stalk rising from the dorsal margin of the base of the tibia. From the base of this stalk a short muscle extends dorsally in the distal part of the femur. The anterior levator of the tibia (Alt) is represented by only a thin strand arising from the base of the tibia. The depressor of the tibia (Dtb) is a long slender muscle arising in the ventral part of the femur and tapering to its insertion on a long apodeme that arises from the knee joint. A small muscle arising on the dorsal wall of the femur is inserted on the apodeme of the depressor of the tibia near its base. The levator (Lta) and depressor (Dta) of the tarsus are two small muscles. the depressor longer than the levator, which arise on the distal part of the tibia and are inserted on the base of the tarsus. The depressor of the pretarsus (Dpt) consists of two small muscles, one arising in the proximal end of the tibia and the other on the ventral wall of the basal half of the tibia. They are both inserted on a long tendon-like apodeme (Tad) arising from the unguitractor plate at the base of the claws.

Abdomen. In Macropathus filifer each segment of the abdomen appears to conform to a similar pattern. The muscles can be divided into longitudinal, dorsoventral and pleural.

Longitudinal muscles, which are divided into tergal (Fig. 34. Ltg) and sternal (Fig. 35, Is) muscles, arise at the anterior margin of each segment, and are inserted into the anterior margin of the segment behind. The tergal muscles form an almost continuous band over the surface of the terga, which is broken by a narrow gap medianly, where the heart runs the whole length of the thorax and abdomen. Eleven pairs of alary muscles (Fig. 41, Am) arise from the terga and spread out fanwise over the surface of the dorsal diaphragm. The sternal muscles consist of two narrow bands connected anteriorly in each segment by a transverse sternal (Fig. 35, Tsn) muscle. Segmentally, just internal to each longitudinal sternal muscle (Fig. 35. Is) arise two small outer sternal muscles, a narrow oblique lateral (Fig. 35. Los), and a small fan-shaped median (Fig. 35. Mos) muscle which originate midway on the eusternite of their own seg

ment and are inserted on the anterior margin of the following eusternite, thus connecting together the adjacent edges of the sterna. The longitudinal muscles function as retractors of the abdomen, and the tergals and sternals working together telescope the abdomen.

Text-fig. 8. Muscles of Genit alia.—Fig. 36—Muscles of female gemtalia. Fig. 37—Muscles of male gemtalia.
Ca, cercal aperture. C cercal muscles. Dv dorsal valve; De, ductus [ unclear: ] , E, endapophysis, Is VIII Is IX, inner sternal VIII. IX, Los, lateral outer sternal IX, Lt. longitudinal tergal, Ma, muscle of anus, Mos, median outer sternal IX, Mp. minor protractor muscle of genitalia; Mpg, major protractor muscle of genitalia; Mts minor tergo-sternal IX; Os IX, outer sternal IX, P, paramere; Pp. paraproct; Pn penis; Pd pseudosternite, R, rectum; St, spermatheca deflected to left, S. IX, sternite IX, 2Ts VIII, secondary tergo-sternal VIII, 3Ts VIII. tertrary tergo-sternal VIII; Its IX, primary tergo-sternal IX 2Ts IX, secondary tergo-sternal IX, 3Ts IX. tertrary tergo-sternal IX 1Ts primary tergo-sternal X. 2Ts. secondary tergo-sternal X; Vs, vesiculae seminales, VV, ventral valve

Dorso-ventral muscles, Figs. 34. 35, consist of primary (1Ts) and secondary (2Ts) tergo-sternal muscles. They arise from the tergum in each segment both segmentally and intersegmentally and are inserted on the sternum. They are concerned with the mechanics of respiration.

Pleural muscles in most insects can be divided into sterno-pleural and notopleural, but in M. filifer these do not occur.

The musculature of each spiracle consists of a short dorsal muscle for closing and a long ventral muscle for opening the spiracle.

Musculature of Genitalia. In segments VIII, IX, and X the muscles are modied for movement of the cerci and genitalia.

Male. Fig. 37. In the male the musculature of segment VIII conforms with that of the preceding abdominal segments, but segments IX and X have undergone various changes. Three tergo-sternal groups arise on tergum X. The primary group (1Ts X) is inserted on the endapophysis (E) of the ramus, the secondary group (2Ts) on the pseudosternite and the tertiary group on the parapioct. The outer sternal (Os IX) arises antero-laterally on sternum IX as in a typical segment and is divided into two groups—the lateral group (Los) is inserted on the ramus, the medial (Mos) on the pseudosternite Thus the pseudosternite is controlled by both tergo-sternal and sternal muscles. Arising on the pseudosternite and inserted on the ramus is the ramo-pseudosternal muscle. The parameres are controlled by two muscles; the parameral muscle arises from the

pseudosternite and is inserted on the paramere, while a transverse parameral muscle acts between the two parameres. The ductus ejaculatorius is covered by two muscular sheets, the major (Mpg) and minor (Mp) protractor muscles of the genitalia, the major lying within the minor. The contraction of these two

Text-Fig. 9. Trachea and Muscles of Head. Muscles of Leg. Fig. 38—Lateral view head showing trachea passing to head capsule and mouth parts. Fig. 39—Anterior view of head showing muscles On left deeper muscles of maxilla, hypopharynx and labium. On right muscles of labium, mandible and antenna. Fig. 9—Shingle disturbed and reported on 26th October. 1951.
Fig. 10—The same area 14 months later December 1952 [ unclear: ] in flower young plants of [ unclear: ] and the grasses [ unclear: ] and [ unclear: ]
40—Muscles of hind leg.
Abm, abductor of mandible; Ac, adductors of cardo; Alt, anterior levator of tibia; Am, adductor of mandible; Arl anterior retractor of labium; As adductor muscle of stipes; Bof, branches to brain oesophagus and eye; Da. depressor of antenna, Dp, dilator muscles of [ unclear: ] ; Dpr, depressor of [ unclear: ] ; Dpt, dorsal prothoracic trunk; Drm. distal retractor of mentum; Dt, depressor of trochanter; Dta, depressor of tarsus; Dtb depressor of tibia; Ef extensor of flagellum; Ff, flexor of flagellum, L branch to labium; La. levator of antenna; Lc, lateral connective; Lpt, lateral prothoracic trunk; Lt, levator of trochanter; Lta levator of tarsus; Ml, branch to mandible and labium; Mp. branch to maxilla and palp; Mv, muscle of vertex; Plt. posterior levator of tibia; Prl posterior retractor or labium; Prm proximal retractor of mentum; Rh, retractor of hypopharynx; Ta. trachea to antenna; Tad, tendon-like apodeme; Tg, trachea to gena; Vpt, ventral prothoracic trunk.

muscles everts the genitalia. The [ unclear: ] belong to the eleventh abdominal segment and are controlled by abductor, depressor and levator muscles (Fig. 36, C) arising on tergum X.

Female. Fig. 36. In the female the muscles of segment VIII have been adapted to assist in the movement of the external genitalia. The inner sternal muscle (Is VIII) arises on the subgenital plate and is inserted on the interior intervalvula. The tergo-sternal muscles are divided into three groups. The primary one (Its IX) is inserted on the subgenital plate, while the secondary has its origin on Tergum VIII (2Ts VIII) and the tertiary (3Ts VIII) arises on the intertergal apodeme on tergum IX; both are inserted on the basivalvula. In segment IX the inner sternal muscle (Is IX) arises on the second valvifer and is inserted on the paraproct. The outer sternal (Os IX) arises on the median

The mouth is situated anterior to the base of the hypopharynx and immediately behind the base of the clypeus. The mouth leads into the oesophagus, a narrow muscular tube, which extends upward in the anterior part of the head, then turns to pass posteriorly beneath the brain but above the tentorium and leaves the head by the occipital foramen. The oesophagus swells out into the very large crop (Fig. 46, C) which fills the whole thorax and the anterior part of the abdomen. It is used for storage of food. It is capable of considerable distention, and when empty or partially full its wall is thrown into folds. The surface of the cuticular lining of the crop contains many ridges and folds which increase in intensity near the posterior end (Fig. 49). Sections of the crop show slight indentations on the dorsal surface and much stronger ones on the ventral surface (Fig. 47). The stronger indentations have serrated margins forming small teeth. The wall of the crop consists of a thick chitinous intima (Figs. 47, 48, Ci) composed of two layers, an inner heavily staining layer (Fig. 53, Il) consisting of numerous fine indentations and chitinous setae, and a deeper, thicker stratified layer (Figs. 53, 54, Ol). Macropathus differs from Stenopelmatus by having indentations in the inner layer of the intima, while that of Stenopelmatus is smooth. The stratified layer is irregular in thickness. Below this is the chitin secreting epithelium (Fig. 54, Cse) resting on a basement membrane with the cell walls not clearly defined. Outside the epithelium is a thick layer of striated longitudinal muscle (Figs. 47, 48. Lm) and surrounding this is striated circular muscle (Figs. 47, 48. Cm). At its posterior end the crop narrows and its chitinous intima increases in thickness and is thrown into six evenly distributed folds, which form the junction of the crop with the gizzard (Fig. 49). Within the gizzard these folds become raised into prominent ridges each bearing 27 large primary teeth (Fig. 49, It), making a total of one hundred and sixty-two. On either side of each row of primary teeth is a row of smaller secondary teeth (Fig. 49, 2T) making twelve rows in all, each row bearing twenty-one teeth. These are the “i lobi a spazzoli” of Berlese (1909) or “barbated lobes” of Du Porte (1918). At the base of the fold, between each pair of adjacent rows of secondary teeth, is a long, dark, heavily chitinous ridge (Fig. 49, Cr) which bears no teeth Thus the full complement of proventricular teeth is four hundred and fourteen, of which one hundred and sixty-two are primary teeth and two hundred and fifty-two barbated lobes. This differs from Stenopelmatus fuscus, where there are two hundred and sixteen proventricular teeth, one hundred and thirty-eight being primary teeth and seventy-eight barbated lobes; and from Hemideina thoracica, where Maskell records one hundred and twenty primary teeth, but did not count barbated lobes. Internally the gizzard is constricted near its anterior end, the teeth on each ridge in this region being large, flattened apically and covered with yellow microtrichia (Fig. 52, Mt). The clefts between them are very shallow. On each ridge, anterior to the constriction, are seven teeth which grow progressively smaller towards the crop They are rounded, slightly cup-shaped on the posterior margin and covered with stiff posteriorly directed microtrichia The most anterior “teeth” project into the crop and are mere projections of tissue tipped with chitin and bristles. In the region anterior to the constriction there are no barbated lobes or long chitinous ridges. Posterior to the constriction the teeth are large, triangular and yellow-brown in colour, with their apices posteriorly directed and sharply pointed with

dark brown chitin. These teeth become progressively smaller as they approach the mesenteron, the posterior two teeth being smoothly rounded with no chitinous points and the clefts between them very shallow. Both the chitinous ridge and the barbated lobes run from the eighth to the twenty-seventh primary teeth. The six folds pass posteriorly from the gizzard into the lumen of the mesenteron so that the posterior end of each forms one of the six flaps of the cardiac valve (Figs. 59, 60). Three of the flaps are large (Figs. 49, 59, Llg), curving inwards to fit together, and form the main or primary section of the valve. Alternating with them are the other three shorter flaps (Fig. 59, Slg) which do not project as far into the mesenteron, but form a secondary basal section to the valve. In both fresh and preserved material they all appear a clear white. The valve acts as a filter, only allowing such food as is properly ground by the teeth to enter the mesenteron The structure of the valve in Macropathus differs from that described for Hemideina and Stenopelmatus. In all three insects there are six flaps, but in Stenopelmatus the two lateral flaps are longer than the other four, while in Hemideina there are two pairs of lateral folds and a dorsal and a ventral fold, each bearing a flap-valve.

Text-fig. 12. Gizzard Fig. 49—Gizzard cut open to show teeth, and convolutions at junction of crop and gizzard
Cr. chitinous ridges, Cwc convoluted wall of crop; Gw, gizzard wall, Llg, large lips of gizzard, 1T, primary teeth, 2T, barbated lobes.

The gizzard is composed of the same layers as the crop (Fig. 51) The chitinous layer is very thin between the teeth but thickens considerably over the teeth ridges, especially over the barbated lobes and the chitinous ridges Most of the surface of the chitin is produced into chitinous microtrichia. A thin layer of chitin-secreting epithelium (Figs. 51, 52, Cse) lies beneath the chitin Beneath the epithelium is a layer of connective tissue in which is embedded longitudinal muscle (Figs. 51, 52, Lm) The primary teeth have three pairs of lateral projections (Fig. 52, Lp) and the connective tissue and longitudinal muscle pass into each projection as well as into the apex of the tooth. They also line the barbated lobes and chitinous ridges. Lining each primary tooth, next to the longitudinal muscle, is a layer of circular muscle (Figs. 51, 52, Cm). The rest of the tooth cavity is hollow (Fig. 52, Cc). The circular muscle does

not project into the barbated lobes (Fig. 51, St) or into the chitinous ridges (Fig. 51, Cr). Surrounding the teeth ridges is a thick layer of unstriated circular muscle and outside this a conspicuous layer of peritoneum (Fig. 51, Pm). The histological structure of Macropathus differs from Stenopelmatus and Hemideina in the possession of a large tooth cavity, longitudinal muscle being present in barbated lobes and chitinous ridges, and the circular muscle not being striated.

Mesenteron. The mid gut consists of the intestine proper and two forwardly directed projections from it, the mesenteric caecae (Figs. 59, 60, Mc), which completely enclose the gizzard, one being dorsal to it, and the other ventral The epithelial layer of each caecum has several deep folds in it. which serve to increase the secretory surface. The histological structure of intestine and caeca is similar (Figs. 56, 57, 58)

The whole of the mesenteron (Figs. 56, 57, 58) is covered with a thin layer of peritoneum. There are three muscle layers—a thin outer layer of scattered smooth longitudinal muscle fibres (Lm) which are more numerous in the caeca than in the intestine proper, a middle thin layer of smooth circular muscle (Cm), which differs from Hemideina where it is striated, and an inner layer of smooth longitudinal muscle This inner layer of longitudinal muscle is not present in Hemideina but does occur in Stenopelmatus Stenopelmatus differs from both Hemideina and Macropathus in having all the muscles of the mid gut striated. Within the muscular layer is a layer of connective tissue (Ct) which, on its inner side, penetrates a little way between the epithelial cells forming thick basal walls or nests (“nidi”) (Cn).

The epithelium of the mid gut forms the greater part of the gut wall Within each of the nests formed by the connective tissue is a mass of cells, the lower ones of which are continually dividing to form new cells The nuclei are very crowded and flattened in the centre of the nest On each side of them, continuing up the nest walls, are the attenuated bases of the mature epithelial cells (Mec). As the cells are pushed outward and upward from the centre, they elongate and the nuclei become first round, then much elongated The outermost cells are fully mature and functional and should bear the striated hem which forms the lining of the intestine This striated hem, however, has never been observed in Macropathus filifer. The outermost cells of each nest eventually collapse during secretion and are lost, and the younger cells next to them are forced outward to fill the gaps Perfectly formed “nidi” are common in the caeca, but not so common in the intestine proper.

Several peritrophic membranes (Ptm) may be seen between the epithelium and the food contents Davis (1927) says, “The peritrophic membrane is an envelope of secreted substance that encloses the food material in the intestine of some insects It is elastic and non-cellular, so that it is not a true membrane”. There has been much discussion as to the origin of the peritrophic membrane Van Gehuchten (1890), working with Ptychoptera larvae, thought it to be a product of special glandular cells at the anterior edge of the mesenteron and Cuenot (1898), Vignon (1899) and Bordas (1905) agree with this Thus the peritrophic membrane would be a single continuous chitinous tube, being continuously formed at the posterior end of the stomodaeum and passing out of the anus surrounding the faeces. Imms (1925) says, “The results of recent research indicate that the peritrophic membrane is continuously secreted by a band of

columnar epithelium. There is a narrow band of striated circular muscle (Cm) and surrounding this are six bands of striated longitudinal muscle (Lm), which extend the full length of the hind gut. According to most authorities there is an inner layer of longitudinal muscle, but no trace of this has been seen in M. filifer.

Colon. Fig. 72. The colon is long and bent back upon itself. It consists of the same layers as the ileum. In the colon the six folds of the ileum are continued. Here they are large and of approximately equal size Between these folds are six longitudinal bands of columnar epithelium (Ce). There is a very thin layer of striated circular muscle (Cm) and outside this the six bundles of longitudinal muscle (Lm) which correspond to the longitudinal bands of columnar epithelium. There is no internal longitudinal muscle.

Rectum. There is a marked constriction at the junction of colon and rectum (Fig. 62, Cjcr). At the posterior end of the colon the epithelial folds become elongated and the epithelial layers between become narrower (Fig. 68). The striated circular muscle increases considerably in thickness so that it is capable of closing the aperture between colon and rectum At the termination of the colon the hind gut widens abruptly into the rectum. The chitinous intima (Ci) is thin and, unlike Hemideina, of an even thickness throughout the rectum (Fig. 67). The epithelium is of two kinds, that of the rectal glands proper and that between them. The latter is much reduced, consisting of six narrow, corrugated strips of thin cuboidal epithelium (Figs. 66, 67, Cbe) with small round nuclei. The presence of this cuboidal epithelium agrees with the statements of Maskell (1927) on Hemideina and Davis (1927) on Stenopelmatus, but differs from the results of Miall and Denny (1886) on Periplaneta and Cameron (1912) on Bacillus rossi where no epithelium is present beneath the corrugated intima Miall and Denny state that in these areas the chitinous lining blends with the basement membrane, while Cameron says that between each two bands is a non-epitheliated interspace, where the chitinous intima becomes corrugated and is closely applied to the basement membrane. There are six rectal glands (Fig. 67, Rg) which are continuations of the six longitudinal bands of columnar epithelium (Ce) of the colon The cell walls are distinct and the nuclei are oval The inner surface of the epithelium and the intima are thrown into ridges and folds. These rectal glands are similar to those of Hemideina and Stenopelmatus. According to Maskell they have no glandular structure but “agree with the description by Chun of rectal glands in Locusta viridissima (quoted by Packard, 1903) Minot has stated that Chun's description is applicable to the Acridiidae he has investigated, and he states that the rectal folds ‘do not offer the least appearance of glandular structure’” Between the rectal gland and the cuboidal epithelium is a structure similar to that described by Davis (1927) as a “gland organ” (Figs. 63, 66, Go). There is a distinct gap between the two epithelia which contains from four to seven small, lens-shaped cells (Go), consisting of a large nucleus surrounded by a thin layer of cytoplasm. On the side towards the lumen, cytoplasmic strands (Fig. 63, Cs) pass out from each cell and attach themselves singly to the chitinous intima (Ci). No thin plate of non-staining chitin for the attachment of these strands such as Davis describes has been observed. Cytoplasmic strands also leave the other side of each cell, and these strands unite to form a cord which passes into the connective tissue This is markedly different from Stenopelmatus where each cell gives off only one thread Here the threads are twined into a cord passing towards the lumen. Davis says,

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  Text-Fig. 17.—Reproductive System Figs. 74-79—Histology of tests showing development of spermatozoa. Fig. 74—Germanium Fig. 75—Spermatogonial cells Fig. 76—Spermatid containing developing sperms. Fig. 77—Spermatid ruptured to release sperms Fig. 78—Sperm bundle Fig. 79—Three sperm bundles grouped together Fig. 80—Dorsal view male reproductive system Fig. 81—Ventral view lower portion of male reproductive system Fig. 82—L.S. follicle of testis Fig. 83—Dorsal view female reproductive system Fig. 84—Mature egg. Fig. 85—Oocyte from posterior end of ovary
  Ac, apical cell, Cd, cytoplasm and deutoplasm, Ch, [ unclear: ] , Co, calyx of oviduct, De, ductus ejaculatorius, Dsz, developing spermatozoa En, endapophysis, Es, epithelial sheath, Et, egg tube; F, follicle; Fca, feebly chitinized arch connecting rami G. germanium. Ga, genital aperture H. heads, Lt, left testis, Mr, muscle attached to ramus N nucleus P pedicel, Pn penis, Ps, pseudosternite, Psh, peritoneal sheath, Rps ramus of pseudostermte Rt, right testis, Sc spermatogonia, Sch, chorion sculptured, Sgc spermatogomal cyst, Sgp, subgenital plate, Sl. terminal filaments uniting as the suspensory ligament, St, spermatidia, Stv, spermatheca. Sz spermatozoa, T, tails; Tvs, tubules of vesrculae seminales, V vacuoles, Vd [ unclear: ] deferens, Ve, vas efferens; Vg, vagina, Vm, vitelline membrane, Vs, vesiculae seminales, Vt, vitellarium, Wa white area.

numerous elongate sperm tubes [ unclear: ] follicles (Figs. 80, 82, F) which are arranged round the periphery and taper inwards. Each sperm tube is surrounded by a thin layer of peritoneum (Fig. 82, Psh) which serves to bind the testis together into a compact structure The sperm tube wall consists of a thick vacuolated epithelial sheath (Fig. 82, Es) According to Snodgrass (1935a) sperm tubes do not have a true follicular epithelium such as that which forms the walls of egg chambers in the ovary. This has been verified in Macropathus filifer.

As in the female egg tube each sperm tube consists of a germanium containing apical cells (Fig. 74, Ac) and spermatogonia (Fig. 74, Sc), a zone of growth containing spermatocysts (Fig. 75, Sgc), a maturation zone containing spermatids (Fig. 76, St) and a zone of transformation containing spermatozoa (Fig. 77, Sz).

The germanium consists of an apical cell surrounded by spermatogonia (Fig. 74). The large apical cell (Ac) is believed to be the primary spermatogonium of the tube which through division gives rise to all the other spermatogonia.

Encysted spermatogonia (Fig. 75, Sgc) are present in large numbers in the zone of growth The origin of the male cyst cells in insects is not definitely known, but, while some investigators have believed that these cells are derived from the sheath of the sperm tube, most writers consider them as products of the germ cells. According to Miall and Denny (1886) spermatocysts are peculiar to Insects and Amphibia Berlese (1909) considers the cyst or nurse-cells and germinative cells (spermatogonia) are differentiated at the blind end of the testicular lobule. Then a number of nurse-cells form a cyst round a number of spermatogonia. Berlese has summarised the views of investigators of his day. “By Sutten (1900) and Voinov the cyst cell is compared to a primary spermatogonium, by Holmgren to an indifferent syneytium, by Paulmier (1899) and Gross (1904) to connective elements. Korschelt and Heider (1902) derive it from an indifferent initial cell Finally Henneguy (1904) considers that the cyst cell ought to be homologised with the ovarian epithelial cell.”

According to most writers the spermatocysts enlarge and undergo spermatogenesis until finally near the vas efferens (Fig. 82. Ve) they contain spermatids (Figs. 76, 77, St) and spermatozoa (Figs. 77, 78, 79, Sz) Maskell (1927) says that in the sperm tube of Hemidema thoracica the spermatozoa are free from one another within the cyst wall, but are found in bundles in the vasa deferentia (Fig. 80, Vd) free from the cyst. In Macropathus filifer, however, mature spermatozoa in bundles are found free scattered throughout the whole sperm tube and are not confined to the end nearest the efferent duct Sometimes the bundles are solitary (Fig. 78) but more frequently several bundles are grouped together (Fig. 79).

With the elongation of the spermatocyst the nuclei within multiply, and pass into the spermatid stage (Fig. 76). The nuclei form the heads of the developing spermatozoa and when they are fully formed the cyst wall ruptures and the sperms are set free (Fig. 77) The spermatozoon consists of three parts—anteriorly a head (Fig. 78, H), then a short middle portion, and posteriorly a very long tail (Fig. 78, T). The sperm bundle consists of three parts also—anteriorly there is a white area (Figs. 78 79, Wa) which curves back postero-laterally on each side, the middle portion is formed by the massed heads of the sperms and posteriorly are the long tails (Figs. 78, 79. T) which propel the bundle along by rhythmic beating.

the hypocerebral ganglion is connected antero-medianly to the oesophageal ganglia (Fig. 89), and not separately to each ganglion The oesophageal ganglia are each connected anteriorly to the deutocerebrum Posteriorly a fine nerve arises from each and passes back to two small, oval bodies, the corpora allata (Fig. 88, Ca), which, according to Iinms (1946), were formerly referred to as posterior oesophageal ganglia. They are now regarded as ductless glands, which secrete hormones concerned in regulating growth.

Ventral Sympathetic System. In M. filifer from the suboesophageal ganglion (Fig. 86, Sog) to the sixth abdominal ganglion (Fig. 86, A6), three fine longitudinal nerves lie one dorsal to and one on either side of the ventral nerve cord. The three nerves pass posteriorly from the suboesophageal ganglion, the two lateral ones each giving off two branches, while the dorsal nerve gives off a pair of lateral nerves just anterior to the first thoracic ganglion (Fig. 86, T1), and terminates on the antero-dorsal portion of that ganglion On each of the first thoracic and first to fifth abdominal ganglia the two lateral nerves loop over the sides of each ganglion to unite below the antero-ventral surface of each respective ganglion From the second thoracic (Fig. 86, T2) ganglion arise a

Text-Fig. 19 Sympathetic Nervous System Fig. 91—Enlarged dorsal view of sympathetic system on third abdominal ganglion and part of ventral nerve cord Fig. 92—Enlarged ventral view of sympathetic system in same region
A3, third abdominal ganglion, Dn, dorsal sympathetic nerve, [ unclear: ] , sympathetic ganglion, Lc longitudinal connective, Lcn, lateral sympathetic nerve, N, sympathetic nerve to [ unclear: ]

pair of nerves going to the metathoracic spiracles The nerves from the third thoracic ganglion (Fig. 86, T3) swell into a pair of ganglia, each of which gives off two nerves, one to the first abdominal spiracle and one to the first abdominal ganglion (Fig. 86, A1) In the first five abdominal ganglia the sympathetic system follows the same pattern, the two lateral nerves (Figs. 91, 92, Lcn) loop over each side of their respective ganglion, while the dorsal nerve (Fig. 91, Dn) passes three-quarters of the way down the ganglion and then turns to the left and fuses with the left lateral nerve The two lateral nerves unite on the antero-ventral surface of the ganglion (Fig. 92) and give off three nerves which pass back to the next ganglion The dorsal nerve runs back along the ventral surface of the ganglion and then passes dorsally to the upper surface of the longitudinal connectives near their anterior point of origin In the sixth abdominal ganglion the dorsal nerve does not fuse with the left lateral nerve but ends on the anterior part of the ganglion The two lateral

compound eye to the occipital suture, the geno-epicranial suture, which is unlike anything found in other Orthopterans so far described. It is possible to speculate that these two sutures on either side of the head are another very primitive condition of M. filifer representing the beginnings of the epicranial suture. As the Insecta evolved, these sutures moved dorsally till they met and fused in the mid-dorsal line as the epicranial suture, so common in most members of the Orthoptera and other groups of insects. The presence of this suture cannot be related back to the Myriapods because there the head capsule is a fused box lacking sutures. If the embryology of M. filifer was worked out it would probably reveal the answer to this problem. However, the fact that several of the common sutures of the insect head are not present here suggests that the head capsule is not primitive and that these peculiar sutures have been secondarily acquired.

The lack of wings in M. filifer has had a marked effect on the structure of the thorax. The pleural wing process is lacking from each segment and consequently the muscles associated with the wings are missing also, so that the greater part of the thorax is filled with muscles for operating the legs The apodemes for muscle attachment in the sternum differ in several ways from other members of the Orthoptera The postfurcasternite present in most insects is absent in M. filifer and the prosternite, although present in the prosternum, is absent from the meso- and metasterna. Perhaps the most important difference is the presence of a small spinasternite with a well developed spina in the metasternum, where it forms the last sclerite of the segment. Snodgrass (1935a) has stated, “It should be observed that the metasternum never has a spinasternite, because the third intersternite either is suppressed or becomes the acrosternite of the first abdominal sternum”. As practically no work has been done on morphology in the Gryllacridoidea it is possible that a spinasternite is present in other members of the group, although this is the first time it has been recorded.

Whether lack of wings in M. filifer is a primitive condition or secondarily acquired is open to discussion According to Imms (1937), “The earliest fossil remains of insects found in Carboniferous rocks were exopterygote forms endowed with large and tolerably efficient wings Along with them are fragments of contemporaneous nymphs, thus indicating that these insects underwent incomplete metamorphosis”. In another part he says, “We are still faced with want of direct evidence from fossils with regard to the two most important problems of insect phylogenv—viz, the origin of the insects as a class, and the origin of wings”. The Protorthoptera which were the ancestors of the cursorial and saltatorial Orthoptera occurred in the upper Carboniferous and show from the structure of their thorax that they had developed “some capacity for running”. One member of this group, Oedischia Brongn, exhibits the characters of a primordial long-horned grasshopper From this it would appear that in the Orthoptera the earliest members of the group were winged and these ancestral forms gave rise to both winged and wingless forms The earliest fossil remains of the Rhaphidophoridae so far recorded are from the Oligocene in Europe, Prorhaphidophora Chopard, 1936, from the Amber of the Baltic, showing it to be similar in structure to members of the family existing to-day Thus loss of wings must have taken place at some earlier stage in their geological history. Examination of M. filifer has shown that there is no trace of any vestigial structure which could be connected with the possession of wings in

the past, but it is possible a study of the embryology may throw some light on the subject.

The alimentary system of M. filifer conforms in its general plan with that of the two other members of the Gryllacridoidea that have been studied—namely Hemideina and Stenopelmatus. However, there are several small points in which it is peculiarly distinctive. The presence of four hundred and fourteen teeth in the gizzard, one hundred and sixty-two primary and two hundred and fifty-two barbated lobes, as compared with two hundred and sixteen in Stenopelmatus fuscus, one hundred and thirty-eight primary and fifty-two barbated lobes, and one hundred and twenty primary teeth in Hemideina thoracica, is of interest because of the much greater number in Macropathus filifer; but comparison of the shape of the primary teeth reveals a difference in structure and shape In both Hemideina and Stenopelmatus the primary teeth are triangular in shape and flattened apically, while in Macropathus, although the superficial appearance is triangular, the teeth are really ovoidal with three pairs of elongate lateral projections. These projections are covered with a thick layer of chitin and contain connective tissue and longitudinal muscle. Unlike the teeth of Hemideina and Stenopelmatus, which are solid, they possess a large central cavity. As far as is known the peculiar structure of the primary tooth is characteristic of Macropathus

Another peculiarity is the presence of a “gland organ” in the rectum similar to that recorded for the first time in insects by Davis (1927) as occurring in Stenopelmatus Although differing in minor details in their structure, the basic pattern in the two insects is the same and they probably have a similar function Stenopelmatus and Macropathus do not share the same type of habitat, Stenopelmatus frequenting semi-arid areas, while humidity is essential to Macropathus. Davis has suggested that the organ may either function as a mucus-gland or be used to remove excess water from the faeces. The latter function would only be of use where conservation of water is necessary, and as Stenopelmatus is found in semi-arid localities it was a natural conclusion for Davis to come to. However, as Macropathus lives under humid conditions, and yet has a similar organ, the need for conservation of water would not be so vital. Thus it seems far more probable that the “gland” functions by secreting mucus to assist in the expelling of faeces Further comparative studies of the alimentary tracts of other members of the Orthoptera may help to solve this problem.

The reproductive system of M. filifer conforms in most respects with that described for other members of the Orthoptera The two main differences are found in the female system Here there is a little flap of tissue attached to the base of the sub-genital plate which, during copulation, may be used to close the vaginal aperture so that spermatozoa, being unable to pass up that way, must go to the spermatheca for storage The other difference is that the spermatheca, unlike that found in most insects, does not open into the vagina, but opens instead on to the lower surface of the copulatory chamber Thus it is not till the egg is on its way to the exterior that it becomes fertilized. There seems to be no real reason for this peculiarity in Macropathus, as it is neither an advantage nor a disadvantage to the insect.

The nervous system of Macropathus is of interest because it has become more complex in structure As the insect avoids bright light, vision is not so essential