Genus 1.--OECETICUS, Guild.
"Ocelli present. Antennæ 1/3, in male strongly bi-pectinated, much more
shortly on apical half. Labial palpi extremely short, rough-haired.
Abdomen in male very elongate, roughly hairy. Legs hairy, tibiæ without
spurs, posterior tarsi extremely short and stout. Fore-wings with veins 4
and 5 short-stalked, 7 sometimes out of 9, 8 and 9 stalked, forked
parting-vein well defined. Hind-wings with veins 4 and 5 stalked, forked
parting-vein well defined, 8 connected by bar with cell beyond middle. An
additional vein (9) rising from 8 beyond bar, another (10) from 8 before
bar, and another (11) from base of costa running into 8 before 10." (See
Plate I., figs. 30, 31.)
"This generic name was wrongly spelt _Oiketicus_ by its originator and
others, for which there is no possible justification. I have corrected
it."--(Meyrick.)
Although I have made several examinations of fully denuded wings of _OE.
omnivorus_, I have been unable to discover any trace of the additional
veins mentioned by Mr. Meyrick. The hair-like scales which clothe the wings
of this insect are very long and slender, and might easily be mistaken for
a short vein, if placed in the requisite position. I am disposed to think
that the examination of undenuded specimens has led to the discrepancy
between the results.
We have one species.
OECETICUS OMNIVORUS, Fereday.
(_Liothula omnivora_, Fereday, Trans. N. Z. Inst. x., 260, pl. ix.
_Oeceticus omnivorus_, Meyr., Trans. N. Z. Inst. xxii. 212.)
(Plate XIII., fig. 6 [M]; Plate III., fig. 26, larva in its case; fig. 25
ditto withdrawn from case.)
This interesting species is seldom seen as an imago in the natural state,
although the cases constructed by its larva are of common occurrence.
Specimens of these cases have been noticed at several localities between
Palmerston, in the North Island, and Invercargill, in the South Island, so
that apparently the insect is common, and generally distributed throughout
New Zealand.
The expansion of the wings of the male is from 1¼ to 1½ inches. _The
fore-wings are very elongate and narrow. All the wings are
blackish-brown, and sparsely covered with scales_, the hind pair being
semi-transparent. The body is very hairy, and deep black. The antennæ are
broadly bi-pectinate at the base, becoming almost filiform towards the
apex. The female insect is apterous, having a close superficial
resemblance to a large maggot. The head and thorax are very small, and
the legs and antennæ rudimentary. The extremity of the body is furnished
with a two-jointed ovipositor, and there are a few scattered yellowish
scales on various parts of the insect. Its length is about 1 inch.
The eggs of this species are deposited inside the old case, which the
female insect never leaves during the whole of her life. The young larva
when first hatched is about 1/8 inch in length. Its head and three anterior
segments are corneous and much larger than the others, which are rather
soft with the exception of the last one. These little {124}larvæ are
extremely active, and immediately after hatching leave the old case, and
roam in all directions over the tree, letting themselves down from branch
to branch by silken threads. They carry the posterior portion of their body
elevated in the air, walking whilst doing so by means of their strong
thoracic legs.
The food-plants of this species are numerous. The following are a few of
them: Manuka (_Leptospermum scoparium_ and _ericoides_, _Cupressus
macrocarpa_, _Pinus insignis_), and various species of willow, &c. These,
it will be observed, include several introduced trees. In fact, the insect
is a very general feeder. About three days after leaving the egg, the
little caterpillar constructs a minute, conical-shaped, silken case, which
it carries almost in an upright position on its posterior segments. Later
on in life this case becomes too heavy to be held vertically, and is
afterwards dragged along by the larva, and often allowed to hang downwards.
The case has two apertures--a large one in front, through which the head of
the larva is projected, and a smaller one at the posterior extremity, which
allows the pellets of excrement to fall out of the case, as soon as they
are evacuated.
Owing to the apterous and completely helpless condition of the female
imago, it is evident that the dispersal of this insect must take place in
the larval state. Distribution is of course quite impossible without a
female being transported in some way, and from observations made on a good
many larvæ of various ages, I am disposed to think that the migration of
this insect to new localities takes place at an early age, possibly soon
after its emergence from the egg. On this account I think that the
occurrence of the moth in both North and South Islands is of great
interest, as it would seem to indicate the existence of some connection
between the two islands, at a period not sufficiently remote to have
allowed any appreciable modification to take place in the insect's
structure and habits. At the same time, it should be borne in mind, that
the protection afforded the larva by its case, and its ability to feed on
so many different plants, may have rendered any modification unnecessary
for the preservation of the species during recent times. The length of the
full-grown caterpillar is about 1 inch. The head is dull yellow speckled
with black. The first three segments are very hard, dark brown, with
numerous white markings. The remaining segments are considerably thickened
near the middle of the insect, rudimentary prolegs being present on the
seventh, eighth, ninth, and tenth segments of the larva. The anal prolegs
are very strong, and are furnished with numerous sharp hooklets, which
retain the larva very firmly in its case. As the caterpillar grows, it
increases the length of its domicile from the anterior, causing it
gradually to assume a more tubular form, tapering towards the posterior
aperture, which is enlarged from time to time. The outside is covered with
numerous fragmentary leaves and twigs of various sizes, placed
longitudinally on the case, and, frequently, near the anterior aperture the
materials, owing to their recent selection, are fresh and green. The
interior is lined with soft, smooth silk of a light brown colour, the
thickness of the whole fabric being about the same as that of an ordinary
kid glove, and so strong that it is impossible to tear it, or indeed to cut
it, except with sharp instruments. The size of the case, when the
caterpillar is mature, varies considerably, ranging from 2¼ to 3 inches or
more in length, and about ¼ inch in diameter, the widest portion being a
little behind the anterior aperture.
During the day the larva closes the entrance, and spins a loop of very
strong silk {125}over a twig, the ends being joined to the upper edges of
the case on each side; in this way it hangs suspended, the caterpillar
lying snugly within. I have often known a larva to remain thus for over
three weeks without moving, and afterwards resume feeding as before; this
probably occurs whilst the inmate is engaged in changing its skin. At night
the larvæ may be seen busily engaged: they project the head and first four
segments of the body beyond the case, and walk about with considerable
rapidity, often lowering themselves by means of silken threads; the only
locomotive organs are, of course, their strong thoracic legs, which appear
to easily fulfil their double function of moving both larva and case. If
disturbed, these insects at once retreat into their cases, closing the
anterior aperture with a silken cord, which is kept in readiness for the
purpose, and pulled from the inside by the retreating larva. This operation
is most rapidly performed, as the upper edges of the case are flexible, and
thus fold closely together, completely obstructing the entrance. When full
grown, this caterpillar fastens its case to a branch with a loop of strong
silk, which is drawn very tight, preventing the case from swinging when the
plant is moved by the wind, and also rendering the insect's habitation more
inconspicuous, by causing it to resemble a broken twig. The anterior
aperture is completely closed, the loose edges being drawn together and
fastened like a bag. The posterior end of the case is twisted up for some
little distance above the extremity, thus completely closing the opening
there situated. It is lined inside with a layer of very soft silk spun
loosely over the sides, and partly filling up each end. In the centre of
this the pupa lies with its head towards the lower portion of the case, the
old larval skin being thrust backwards amongst the loose silk above the
insect.
The male and female pupæ may very easily be distinguished. The male pupa is
rather attenuated, and has all the organs of the future moth plainly
indicated on the integument, as is usual with lepidopterous pupæ. The
female pupa, on the contrary, is merely a chain of segments, with a few
faint indications of rudimentary organs on the anterior extremity. It is,
moreover, much larger than the male pupa.
The insect remains in this condition during the winter months. About
September the male pupa works its way down to the lower end of the case,
forces open the old aperture there situated, and projects the head and
thorax, the pupa being secured from falling by the spines on its posterior
segments, which retain a firm hold in the silk. Its anterior portion then
breaks open, and the moth makes its escape, clinging to the outside of its
old habitation, and drying its wings.
The perfect insect must be about from September till December, but I have
never then observed it. The only specimen I have seen was noticed flying
very rapidly in the street in Wellington, in July. I was at first unable to
tell what species it was, as it had a most unusual appearance on the wing,
but its subsequent near approach enabled me to ascertain for certain that
it was a specimen of this insect. In captivity I have also noticed the
extreme activity of the male when first emerged. Indeed this moth is so
vivacious, that it often happens, owing to the emergence usually taking
place very early in the morning, that specimens are more or less injured by
their efforts to escape, before they are discovered in the breeding cage.
This restless energy of the male is no doubt essential to the insect's
well-being, as the females, hidden away in their cases and incapable of any
movement, must of necessity be very hard to discover. The power of
locomotion lost in the one sex is thus doubled in the other. Considering
the protection {126}afforded this insect by the case, which it inhabits
during its preparatory stages, its enormous mortality from the attacks of a
parasitic dipteron (_Eurigaster marginatus_) is very remarkable. In this
connection the following analysis of 38 cases, gathered at random, may be
of interest:--
26 had parasites.
8 were dead.
2 contained eggs.
2 contained living pupæ, 1 male and 1 female respectively.
Amongst some of these parasites I once obtained a specimen, which was in
its turn infested by a secondary or hyper-parasite, belonging to the genus
_Pteromalus_, in the order Hymenoptera. Eighteen of these minute insects
emerged from a single pupa of _E. marginatus_. The method by which the
_Pteromalus_ introduces its eggs into the dipterous larva, which is in its
turn enclosed in a caterpillar, is not at present known to entomologists;
but it seems probable that the eggs of the hyper-parasite are either
deposited in the eggs of the dipterous insect, or else on the very young
larvæ, before they penetrate the skin of the caterpillar.[66]
Genus 2.--OROPHORA, Fereday.
"Ocelli present. Antennæ 2/3, in male moderately bi-pectinated
throughout. Labial palpi rudimentary, hairy. Abdomen densely hairy.
Fore-wings with veins 4 and 5 short-stalked, 7 and 8 out of 9. Hind-wings
with veins 4 and 5 stalked, parting-vein well defined, 8 connected by bar
with cell beyond middle, and additional vein (9) rising out of 8 before
bar."
We have one species.
OROPHORA UNICOLOR, Butl.
(_Psyche unicolor_, Butl., Proc. Zool. Soc., London, 1877, 381. _Orophora
toumatou_, Fereday, Trans. N. Z. Inst. x. 262, pl. ix. _Orophora
unicolor_, Meyr., Trans. N. Z. Inst. xxii. 212.)
(Plate XIII., fig. 7 [M].)
This odd-looking little insect has been found by Mr. Fereday, at Rakaia.
The expansion of the wings is hardly 1 inch. _All the wings are rather
broad, rounded, and very sparsely covered with dusky brown hair-like
scales_; the body is very hairy, and the antennæ are slightly
bi-pectinated. The female is apterous.
The life-history is thus described by Mr. Fereday: "I have never seen the
larva. Its case measures in length about 16 lines (1-3/8 inches); the
exterior is covered with pieces of stems of grass from a line to 5 lines in
length, laid longitudinally and in the manner of thatch; the interior is
thinly lined with fine silk. The cases are found fixed to the twigs of the
Wild Irishman (_Discaria toumatou_), but it may be inferred from the
covering of the case, that it probably does not feed on the shrub but upon
the tussock grass, generally growing where the shrub is found. It is some
years since I found the cases on _Discaria toumatou_, growing in the
river-beds of the Rakaia and Waimakariri, on the Canterbury Plains, and I
did not find any case in its earlier stage before the larva had fed up and
changed into the pupa state."[67]
All Mr. Fereday's specimens were bred from the cases, and to the best of my
belief no one has ever observed the insect on the wing. It is evidently a
very scarce species, and is probably restricted to a few river-beds in the
South Island.
{127}VII.--THE TORTRICINA.
Not dealt with in this volume.