Go to National Library of New Zealand Te Puna Mātauranga o Aotearoa
Volume 47, 1914
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No. 3. Venusia verriculata Feld.

Cidaria verriculata Feld., Reise der Nov., 5, pl. cxxxi, fig. 20. Phibalapteryx verriculata Butl., Proc. Zool. Soc. Lond, 1877, p. 396. Panopoea verriculata Meyr., Trans. N.Z. Inst., xvi, p. 62. Pancyma verriculata Fereday, Trans. N.Z. Inst., xxx, p 338. Venusia verriculata Hudson, N.Z. Moths and Butterflies, p. 53, pl. 6, figs. 30, 31. Pancyma verriculata Meyr., Trans. N.Z. Inst., xviii, p. 184. Venusia verriculata Philpott, Trans. N.Z. Inst., xxxiii, p. 175; ib., xxxix, p. 216: Hamilton, Trans N Z Inst., xliii, p. 121: Watt, Trans. N.Z. Inst., xlvi, p. 80.

The Egg.

For detailed description, see Trans. N.Z Inst, xlvi, p. 80.

Egg-laying.

The ova are deposited in small regular batches of a dozen, more or less. The parent moth is careless as to the spot where she lays her ova, for they may be found on both dead and green leaves alike. It would appear from the rapid colour-changes in the egg and the extreme activity of the newly hatched larvae that the correct place for the ova is on the dead leaves, and they are often to be found there on the under-surface near the base of the leaf, where they are greatly protected by their colour. Those eggs laid on the green leaves only gain protection on account of their colour for a couple of days or so, and for the remainder of the oval period are startlingly conspicuous; in consequence the collector is bound to come across them in such positions, and, as they are well-nigh invisible on the dead leaves, his opinion is likely to be prejudiced as to the natural place of deposition. Personally, I have found more ova on the dead leaves, where they have invariably been placed on the under-surface, near the butt, than on the fresh leaves, on which they appear to have no fixed position. One female reared in captivity laid a total of 393 eggs in three days. Oviposition was carried on during the night. In most of the batches the eggs are laid in neat rows, being placed end on end, but occasionally they are to be found in a rather scattered condition.

The Larva.

1st stadium: Head of medium size, non-retractile. Abdominal segments 1 to 6 inclusive are largest and equal in size; the 7th abdominal and the thoracic segments about equal. Body cylindrical; prolegs on abdominal segments 6 and 10 only, situated posteriorily, well developed, crochets on lateral flange. A very minute and scattered pile may be observed on the body with a high-power objective. The 6th abdominal segment is divided centrally into two subsegments; on the other segments subsegmentation is not apparent. Spiracles small, circular, rims brown, inconspicuous. The prothoracic shield is slightly raised and light in colour, with a well-marked medio-dorsal suture; each half of the scutum bears 4 minute tubercles and setae arranged in diamond formation. All setae are simple. Tubercle i is contained in the scutum on the prothorax; in the remaining two thoracic segments is above ii, slightly anterior; in the abdominals i and ii are some distance apart, i being anterior to and above ii. ii is also included in the prothoracic shield. iii consists in the thoracic segments of two minute tubercles, sometimes free, sometimes coalesced; in the prothorax they are situated just beneath the scutum, the upper one

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being slightly posterior; in the meso- and meta-thorax the position is some distance beneath but anterior to i and ii, and the position of the two tubercles reversed—that is to say, the upper one is anterior, instead of posterior as in the prothorax. In the abdominal segments iii is pre-spiracular, below but anterior to i; appears to be absent in the 9th abdominal. iv is absent in the thoracic segments, but in the abdominals is post-spiracular, immediately beneath ii, and slightly subspiracular. v is a large tubercle in the prothorax having one large and one small seta, is pre-spiracular and beneath iii; consists of a single-hair-bearing tubercle beneath iii in the meso- and meta-thorax; in the abdominals is subspiracular beneath iii, and in the 9th abdominal immediately beneath iv. vi and vii are coalesced in the 1st thoracic segment, situated above the leg, vi anterior to vii; in the 2nd and 3rd thoracics vii is situated above the outer posterior margin of the leg, posterior to v; is absent in the abdominals. vi is also absent in the abdominal segments. viii is a very minute tubercle on the ventral surface anterior to vii, immediately beneath v in the 9th abdominal. Two secondary setae are situated on the ventral surface anterior to viii. 2nd stadium: The thoracic plate is not distinguishable on the prothorax. Tubercles i, ii, iii, v, and viii as in 1st stadium. iv now appears in the 2nd and 3rd thoracic segments above and posterior to v. A small secondary tubercle is situated just beneath and slightly in front of v in the meso- and meta-thorax. vi appears in the first seven abdominal segments immediately beneath the spiracle and beneath but posterior to v. vii in the abdominals is beneath iv, immediately posterior to vi, except in the 6th segment, where it is situated on the upper and outer margin of the leg. This is the final arrangement of the tubercles, and remains constant throughout the 3rd, 4th, and 5th instars. 3rd stadium: Abdominal segments 6 and 7 are divided medially into two equal subsegments. Pile exceedingly minute. 4th stadium: As in stadium 3. Spiracles circular, excepting those on the first thoracic and 7th and 8th abdominal segments, where they are inclined to be oval.

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Fig. 14.—Larval tubercles: 1st instar.
Fig. 15.—Larval tubercles: 2nd instar.

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5th stadium: Spiracles oval, brown. Subsegmentation on abdominal segments 1 to 7. Pile thick but very minute. Body of equal width throughout, slightly flattened dorsally and ventrally. The head is medium-sized, somewhat square in shape; clypeus small and distinct, possessing 4 minute setae; either cheek has 7 setae, the area included by the eyes bears 4 with a 5th more remote; mandibles serrate, with 5 points.

Development of Larval Markings.

1st stadium: General colour light green. Head light green with light-brown mouth parts; eyes black. Has a conspicuous brown spiracular line. Tubercles light-coloured. 2nd stadium: Broad medio-dorsal stripe of dark green. Spiracular stripe dark brown to black. 3rd stadium: A light-brown stripe extends from either side of the base of the clypeus to the top of the head, but they are some distance from the central facial suture. 4th stadium: A very narrow white subdorsal line appears on either side of the broad medio-dorsal stripe. Cheek-stripes ochreous and very conspicuous; while a third short thick stripe occupies the central portion of the clypeus. The tubercles are still light in colour, excepting iv, which is included in and is of the same colour as the spiracular band. 5th stadium (full-grown): General colour green, ventral surface light. The narrow white subdorsal stripes are margined on either side by a pinky area. Tubercles black. Head-markings very strong, as in last stadium, the facial markings extending across the prothorax, where they are black. Suranal plate and upper portion of anal prolegs black. Before spinning the whole body assumes a rosy hue.

Variation in Larva and Imago.

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The Larva.—Here there is not much variation, chief instances being the absence of the spiracular lines and cheek-stripes, and in the coloration of the tubercles. There appears to be a variety which is, when full-grown, larger (11/16 in. to 1¼ in. in length), greener in colour, and not having such marked subdorsal lines. This may be explained sexually.

The Imago.—A certain amount of variation occurs in size and colour, some specimens being brighter in the shades of brown than others.

Table of Periods.

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Period of incubation from fifteen to twenty-two days, or longer. 1st stadium: fifteen days; length on hatching, 1/16 in. 2nd stadium: thirteen days; length after 1st moult, 3/16 in. 3rd stadium: thirteen days; length after 2nd moult, 5/16 in. 4th stadium: twelve days; length after 3rd moult, 7/16 in. 5th stadium: twenty-one days; length after 4th moult, 9/16 in. Larva, full-grown, ¾ in. to 1¼ in. in length; length before pupating, ½ in. only; duration of spinning, about two days; duration of larval life within the cocoon, four to five or more days; duration of pupal existence, fifty days (winter months).

Habits.

The young larvae on hatching do not eat the empty shells, but almost immediately start climbing. At first they are very active, and able to crawl long distances, betaking themselves to the innermost leaves of the cabbage-tree, where they are wont to congregate together on the upper but inner surface of the loose outer leaves forming the heart spike of the tree. Throughout the first four stadiums their method of feeding is to scoop long channels

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out of the surface of the leaves parallel to the fibres; later, however, in their 5th stadium, they attack the edges, eating out great lumps, which, as the leaves grow and begin to droop outwards, give to them a very notched and serrated appearance. It is unfortunate that the larvae attack the youngest leaves, for it is not till these grow up that the tree shows any sign of the presence of caterpillars, and then it is nearly always too late to do any good, unless there be a second or third brood, for the larvae will in all probability have retreated to the mass of dead leaves hanging around the tree, or among the rubbish on the ground, to pupate. On carefully pulling apart the outer leaves of the inner spike one is almost certain to find numbers of larvae in all stages of growth, the younger ones being generally found in groups. No sooner, however, are the leaves opened than the larvae will immediately drop into the crevices, many being crushed to death when the leaves resume their former position on being released. One would think that in extremely wet weather many would stand a good chance of being drowned in the water that collects round the base of the leaves, but they may frequently be found wallowing in this, seemingly without the slightest harm. Specimens in captivity invariably kept to the underside of the leaves of the food plant, but in a state of nature they are frequently to be found feeding fully exposed on the more mature leaves; here they probably enjoy the warmth of the sun. Full-grown larvae are never to be found in such exposed situations unless searching for a suitable place in which to pupate. Throughout all the stadiums the larvae make use of a silken thread. When disturbed they do not throw the head from side to side or curl up, as most caterpillars, but either drop or hurriedly seek to hide themselves in the spaces between the leaves. The young utilize the thread for dropping from leaf to leaf in search of food. The silk is exceedingly strong and elastic. Trees that have been badly infected will be found to be almost destitute of the inner compact and succulent heart, while great quantities of the coarse frass will be piled up around the base of the leaves. The larvae during the last stadium have enormous appetites, and it is at this period that most of the damage to the tree is done. Many appear to suffer from a wasting disease; they quit feeding, and the segments gradually wither up till the head is out of all proportion to the rest of the body. Such larvae invariably die, death in all probability being caused by Ichneumons attacking vital internal organs.

The Imago.—As has been recorded by Fereday and others, the moth frequents the dead leaves hanging from the head of the tree, and invariably sits across the leaf with wings fully spread, which accounts for the peculiar markings of the upper and lower wings, these corresponding to similar lines on the leaves. It is the underside of the dead leaves, where these markings are most distinct, that forms the chief resting-place of the moths. It is in this way that the species is wonderfully protected and almost invisible to an untrained eye. Flight is rather slow, and the moth is nocturnal. Season, September to May.

Food Plants.

Cabbage-tree (Cordyline australis; Maori, ti-kouka); Cordyline Banksii.

Parasites.

Phorocera nefaria: The larva of this large blue Dipteron is an internal parasite, emerging to pupate when its host is in the pupa state. Syrphus ropalus Walk.: The larvae of this fly scour the cabbage-tree heads and

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boldly attack and devour all the V. verriculata larvae they come across. Further information on the above two species will be given in future contributions. Cermatulus nasalis has also been found attacking the larvae.

The Cocoon.

The cocoon is thin and scanty, and is composed of a rather coarse brown silk, which is extremely viscid. When viewed through the microscope the individual threads are bespangled at regular intervals with globules of sticky matter, very similar to the web of a spider. Favourite places for spinning are at the base of the leaves up against the trunk of the tree, in the crevices of the bark, and amongst the dead leaves hanging around the stem.

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Fig. 16.—Pupa: Frontal view. a, prothorax; b, 1st spiracle; c, antenna; d, epicranium; e, eye.

The Pupa.

Immediately after the last moult the wings, head, and limbs of the pupa are green; the anal segments are light pink, with a strong reddish medio-dorsal stripe; the prothorax is pink or rather reddish, and at the juncture of the segments the pink coloration is very marked. Within twenty-four hours the pupa passes through several shades of brown till it is very dark, almost black; the intersegmental membrane between the movable segments is much lighter in colour. The frontal headpiece has three slight prominences, one on either side at the base of the antennae, the 3rd ventral, above the labrum. The thoracic segments bear no very marked dorsal hump, while the abdomen is inclined to be short and stout. Abdominals 5 and 6 alone are movable. The cremaster is short and stumpy, bearing 4 whorled hooks, two on either side, and slightly dorsal. Dorsal view: The head is slightly depressed between the antennae, and not visible. The prothorax is narrow, with a central suture, and is somewhat pitted and wrinkled. The 1st spiracle has a long narrow opening, and is very conspicuous. Both the meso- and meta-thorax bear a strong central suture, and are wrinkled. The abdominal segments are strongly pitted, and bear minute hairs that correspond in position with the larval tubercles, but are very hard to distinguish. There is no trace of subsegmentation. The 5th, 6th, and subsequent abdominal segments are swollen anteriorly; this is very marked on the sides and dorsum. The hindwings show a very narrow strip, widest at the 1st abdominal, rapidly narrowing in the 2nd, and again widening slightly in the 3rd and 4th abdominals. Lateral view: The apex of the head is in front of the axial line. There is a deep depression in the maxillae some little distance from their origin; from this depression they slope outwards to their extremities near the posterior margin of the 4th abdominal segment; from here the abdominals taper uniformly and rapidly to the cremaster. The whole length of the antenna is visible, the base being level with the top of the eye; it rapidly widens out till on a line with the bottom of the eye, and then gradually narrows towards the tip; every joint is plainly visible. A very slight margin of the hindwing can be seen at the 1st and 4th abdominals. In the forewing Poulton's line is absent, though slight venation can be distinguished. The spiracles are very prominent on raised bases, and are dorso-lateral, oval. Ventral view: The

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maxillae have their greatest width on a line with the bottom of the eyes. Here they form an angle with the eye, and rapidly converge to the end of the 1st legs, where they are extremely narrow, widening out again club-like beyond these again to the end of the wings. The antennae and 2nd legs also reach to the end of the wings. Both legs and maxillae are covered with minute transverse rugae, while the wings are sculptured with labyrinthine wrinkling, and the abdominal segments are pitted most anteriorly. The 2nd legs bear an equal width their whole length. Anal scar very prominent. Genital organs inconspicuous, but restricted to their respective segments.

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Fig. 17.—Pupa: Lateral view.
Fig. 18.—Pupa: Ventral view.
Fig. 19.—Pupa: Dorsal view.

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Chief Measurements of Pupa.
Measurement at Distance from Front. Transverse Diameter. Anterior-posterior Diameter.
Mm. Mm. Mm.
Depression in maxillae 1.80 4.00 2.90
End of maxillae 8.70 3.85 3.80
Spiracle, 5th abdominal segment 9.50 3.70 3.35
Spiracle, 6th abdominal segment 10.55 3.30 2.90
Spiracle, 8th abdominal segment 12.00 2.25 1.75
Extreme length 14.00

Dehiscence.

The headpiece, with the eyes and the thoracic and abdominal appendages intact, separates in one piece from the wing-cases except at their tips; the pro-thorax splits down the central dorsal suture; the meso- and meta-thorax remain intact.

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Imago.

The imago has already been completely described by Meyrick (Trans. N.Z. Inst., xvi, p. 62) and by Hudson (N.Z. Moths and Butterflies, p. 53, pl. 6, figs. 30 and 31).

Distribution.

Waitakarei Ranges (Auckland); Wanganui, very common from August to May; Wellington; Christchurch and Dunedin, from October to May; Ashburton; West Plains; Invercargill, taken at light in April.