Liothula omnivora, n.s.
Expanse of wings—14.5 lines.
Length of body—8 lines.
Hab.—Canterbury, New Zealand, especially in the neighbourhood of Christchurch.
Fig. A represents the male perfect insect. Larva varying from light to dark dull brown, mottled with dirty white, sometimes with a pinkish
shade. Head and three first segments retractile. The cases of full-fed larvæ vary in size from 1.½ to 3.½ inches, long, narrow, and tapering, colour varying from light to dark grey, generally smooth but sometimes ornamented with pieces of twig or leaves laid on longitudinally in somewhat regular order, inside thickly lined with fine brown silk. The case is exceedingly tough. I have tested its strength and found that fracture takes place at 32 lbs. The larva is found feeding on all kinds of trees and shrubs, both evergreen and deciduous, not even rejecting the common laurel, and I have named the insect omnivora on that account. I noticed it first on willow trees, when I came to the colony in 1862. Willow, wattle, and coniferous trees appear to afford a particularly favourite food. The cases found on the willow and wattle are generally smooth and plain, but those on the coniferous trees are frequently embossed with small pieces of twig and foliage laid on longitudinally in an order that seems to indicate design. Until fully grown the larva moves about with the case from leaf to leaf feeding with its anterior segments and prolegs extruded. Attached to the interior of the mouth of the case are silken threads which the larva, when disturbed, draws so as to close the orifice. The larva before assuming the pupa state fixes the case by repeated bindings of silk round a twig, as shown in plate IX., on firmly attaching it to the trunk of the tree. The larva whilst feeding suspends the case by a thread. The case is very small at first, the larva commencing to form it soon after birth; and, as the larva increases in size, so is the case enlarged, the larva adding to it from time to time as a mason builds a chimney. Fig. 1 represents a case fixed to a twig of willow with the pupa skin extruded; fig. 4, a case containing a partly-grown larva as suspended when at rest.
Notwithstanding the security afforded by the case, a dipterous insect (somewhat resembling a common bluebottle-fly, but not larger than a common house-fly) is very destructive to the larva. I have found as many as nine out of every ten cases filled with the cocoons of the fly. The fly (fig. 2) is represented at rest on the case.
I find the cases have become much less common in my garden than formerly, which I attribute to the increase of birds.
Fig. 3 represents a portion of the branch of a larch fir, with a case of this insect attached. The silk wound round the branch prevented the return of the sap, and caused an extraordinary swelling of the upper part of the branch. It was found by Mr. James Townsend, at Christchurch.