Art. III.—Notes on a Native Species of Mantis.
[Read before the Philosophical Institute of Canterbury, 7th January, 1883.]
This insect has been observed in several localities during the last three years. It appears to be widely distributed in this island. We first heard of it as having been taken in a garden at Riccarton, a short distance from Christchurch. Soon afterwards, through the kindness of Mr. Nalder, specimens were obtained at Akaroa. It has been found at Amberley, forty miles north of Christchurch. Walter Potts, in the month of April last, discovered it on some flowers in a garden so far south as Clyde, which lies inland in the Otago Lake District, and plentifully in and about Cromwell.
The young emerge in the spring months in numbers; from a single egg-case perhaps as many as twenty or more may appear. We have known them make their way out early in September, at intervals throughout that month and part of the next till the 24th October. At first they are of a pale pea-green or pale green on the limbs and under-parts, above brown or purplish-black, with the eyes very prominent, and a bluish spot on the anterior limbs. The bright green larvæ sometimes appear crowded together when forcing their way through the lids of the egg-cases. At this time they measure some 5 or 6 lines in length. As soon as they have quitted their prison-homes they exhibit great activity in their movements, swiftly coursing hither and thither; perhaps at no other period of their existence do they display so much restlessness.
The body is usually so carried that the lower part of the abdomen just clears the ground; only the two lower pairs of limbs are generally required for locomotion, the anterior pair are kept folded. It may be noticed that the posterior pair of limbs are most robust, and longer than the middle pair. The insect in its larval state not only runs with great swiftness, but it can leap several inches at a bound, a feat that is rarely performed. In running the body is kept nearly upright. At the same time that we note the energy of its movements, it must not be omitted that there are seasons in which it displays an almost inexhaustible power of “masterly inactivity.” These times of quiet, when it remains so long motionless, or nearly so, may be a part of its tactics for securing the presence of victims within reach of its fatal arms. The most difficult feat it is seen to perform is the recovery of its proper position when lying on its back on a plane surface, often for a long time it kicks and struggles in a very helpless manner. The feet are adapted for travelling over a polished surface, such as glass presents; the figure can be easily depressed so as to appear nearly flat. The anterior limbs, only occasionally used as legs, are kept carefully cleaned, particular attention is paid to the blade-like teeth with which these limbs are armed.
When about making an attack it approaches its intended prey near enough to secure it with a dash, its movements are sometimes slow, deliberate. It stands with its anterior limbs folded with an innocent rather than a menacing air, now and then raising itself or lifting the prothorax in a stealthy, quiet manner, as if to judge accurately of its distance; or the head is turned as the victim moves, and with one swift dart the insect is secured. In considering the manner of the manipulation of its food, it must be remembered that it only consumes living insects; it displays remarkable coolness and positive indifference to the sufferings of its prey. Let us suppose it has caught a house-fly; this is held securely on the teeth of one of the anterior limbs, both arms are used and brought to the long tearing or cutting mandibles; it commences the feast usually by taking off some morsels from the head, the fly struggling, kicking or vibrating its wings; various parts are deliberately severed notwithstanding these strong protests on the part of the fly; some of the parts so cut off are rejected, notably wings and legs, other portions of the wretched fly are cut off into edible morsels. During the progress of the meal, the posterior pair of limbs are held rather wide apart and securely planted to resist the efforts of the struggling fly. The Mantis holds on steadily as it feeds, employing both forearms, deliberately plucking its prey away from the mandibles by a downward and forward action; whilst masticating a portion taken off, the anterior limbs are held extended a short distance from the mouth till it is ready for a fresh bite, when the tearing process is repeated. It discloses something of the fastidiousness of the gourmět in selecting only certain parts of the fly for consumption, much of the carcase being neglected and cast away; occasionally it has considerable difficulty in ridding the teeth of these remains; sometimes these are cast off with a single shake of the limbs, or several attempts are required to effect this; so powerful are the efforts at times that the insect itself recoils bodily. Whilst eating, the fine hair-like antennæ are kept nearly upright, or they are slightly moved forwards and back again to an almost vertical position; the mandibles project from over the mouth; the head is moved and turned freely. In drinking, which is seldom indulged in, the body is bent so that its form is slightly curved.
It is quite possible that so much of the body of the fly is rejected because it has ceased to exist under the tearing of the mandibles; we have never seen the Mantis attempt to feed on a dead insect; it may be its special function to exist on living food. The posterior limbs are employed not only to assist in supporting the body, they act also as feelers to ascertain the security of a foothold or to clasp firmly a leaf or spray and thus enable the insect to hang downwards whilst the forearms are folded ready for action.
It will attack any small moving thing that it is likely to be able to hold, such as flies, moths, spiders, etc., we have often seen it with a fly in the teeth of each anterior limb; young of its own kind are devoured as readily as any other food. Its appetite is at times voracious, as we have seen it kill and devour parts of fourteen small flies within a very brief space of time; it can pick a small spider from off its web with singular dexterity. With all its cruelty or ferocity it is timid, retiring from the contact of anything that touches it suddenly; often it retreats before the boisterous blue-bottle-fly. The house-fly is a favourite prey; in pursuit it steadily traverses the smooth surface of window-panes, the structure of the feet allowing it to pass over the lower surface of glass at almost any angle. We have kept many of these insects in a room where they seldom left the windows during the daytime, getting their own food in ample supply. It is worth noticing that flies often approach this terrible enemy as though heedless of its presence, or in some way fascinated by its appearance. When climbing an upright branch the ascent is made in a spiral direction, sometimes all the limbs are used in climbing; should a couple meet suddenly, they at times spar at each other, but as far as we have observed these hostile movements have been unattended by the infliction of any damage.
At the time of its periodical moults it is dull and listless, not caring for food. The casting of the skin, which takes place at intervals during the larval state, is accomplished by throwing itself on the back, when with numberless struggles it wriggles out of its old covering. Gradually the figure of the insect widens and the rudiments of the future wing-processes are developed, these make marked progress after each moult. The cast coverings are discarded in one piece generally, showing the form of the antennæ, of the claws, of the teeth of anterior limbs, etc.
The sexes may be distinguished by a slight difference of form, that of the male is the more slender, the antennæ are more produced; in the perfect insect the wings of the female are not so long in proportion to the rest of the body as those of the male. The perfect insect exhibits also some difference of colouration, the bright light green gives place to a duller tone, the edges of the keeled sides of the prothorax assume a dull amethystine tint, a deeper tinge of a similar hue stains the limbs in various parts, the teeth of the forearms being thus coloured; the blue spot around the auditory organs is very noticeable.
It is particular in cleaning and dressing the head; the action of the fore-limb as used for this purpose, at once reminds one of the manner in which a cat passes its paw over ears and eyes.
The perfect insect does not, except on occasions, walk so nearly erect as in the larval state; it seldom uses its wings or only for a brief flight, we have but rarely seen it make a flying dart at its prey. Its colour harmonizes
so well with many kinds of leaves, that it is difficult to distinguish the insect when lodged thereon, this kind of protection has probably caused it to be frequently overlooked. We believe it to be affected by atmospheric changes; when a low temperature prevails it is dull and sluggish; hence the locality of Clyde has been particularly mentioned, as there a considerable range of temperature is experienced.
The reproductive habits seem to offer some peculiar features, which removes it from those of many other forms of insect life, these are therefore given in detail as facts of interest. At or near breeding time the male is restless, the female is ready for pairing in about ten days after assuming her perfect form, and usually receives the male without any previous demonstrations of courtship on the part of her mate, further than a somewhat close companionship; sometimes, yet rarely, the male chases and leaps on the female. The time of congress is prolonged and varies in duration, it frequently occupies from two to four hours; the operation is repeated from day to day; a pair kept secluded in an ample enclosure were observed to be in congress daily from the 11th of January to the 18th, both days inclusive, again on the 20th, on this date separating at 7 p.m.; they were again united at 9 p.m., remaining in that state till 1.30 a.m. on the 21st.
During their union, both insects keep the anterior limbs folded, the male having often all his limbs clear of the ground, yet so bent as to enable him to cling securely to the female, or sometimes partly supported by the base and part of the outer edge of a portion of one of the wings. The wings of the female remain closed; access is sometimes obtained rather sideways, in which case the wings are partly thrust aside. During the operation, in the female a series of brown-coloured stigmata are freely displayed and become apparently inflated or depressed as the female raises or depresses part of her body.
After the abdomen of the female becomes distended, for some days she appears dull and drowsy, with appetite less keen; when about ten days have elapsed, she makes that curious egg-mass, from which the young in due course come forth. The formation of the egg-mass is a very interesting sight, all her limbs are employed in sustaining her during the proceeding; a quick lateral motion of the lower part of the body accompanies the deposit of the bright glittering material which, as it dries, sticks fast to the article on which it is placed. When first extruded, the matter shines or glistens like very minute bright bubbles or granules; it is smoothed and shaped by the distended orifice, whilst the ovipositors are trained over the centre of the top of the mass. The egg-masses measure from ½ inch to more than 1 inch in length, formed of a series of inclined horny cells, with a sloping
membranous lid, the spaces between the lids filled with a soft white froth-like substance, the whole series of cells being fastened together on each side by a strong layer of chitine. Each cell is .05 or .06 inch in breadth.
After this great labour is completed, the female remains for some hours still as though thoroughly exhausted, her attenuated form shows to what an extent her bulk has been drawn upon to furnish material for the egg-cases. In a short time her vigour and appetite return, and she is again eagerly catching here living prey. After the lapse of a few days, her form again becomes distended, and she is ready for the formation of a fresh egg-mass.
Five or six of these masses are usually made by one female of one pair under observation. The first egg-case was finished on 16th January, at 5 a.m.; a second one was made on the 25th of the same month, at 11.45 p.m. These structures soon lose their brilliancy, and become of a dull whitish colour, which gradually darkens to brown. They are often placed in an irregular group. The female visits them and stands over them at times. In a warm room the young leave the egg-case in about fifty days after the eggs are deposited.
Note by Professor Hutton.
Specimens of the insect, whose habits are here described, were sent by me several years ago to Mr. Wood Mason, but I do not know if it has as yet received a name. The following diagnosis will be sufficient for recognition:—
Animal green; the anterior coxæ and costal vein of the wings yellowish: a bright blue spot on the anterior femora around the auditory organ. Head smooth, wider than the thorax. Prothorax keeled, with a groove on the keel anterior to the suture; rough. Wings of uniform texture. Anterior limbs with the coxæ finely denticulated on each side: lower margin of the femora with 15 teeth, alternately larger and smaller, on the inside, five longer ones on the outside, and four in the median line near the auditory organ, one of which is larger. Tibia with 12 teeth on the inside and 11 smaller ones on the outside, increasing in length distally; the apical tooth very long and curved.
Male.—Length, 1.15; of pronotum, .37; of elytra, 1.01 inch.
Female.—Length, 1.2; of pronotum, .32; of elytra, 1.10 inch.