Semiocosma platyptera (Plate [XII]., fig. 8, 8a larva, 8b pupa).
This is one of the largest of the Tineidæ found in New Zealand, measuring fully fifteen lines across the expanded wings. Its larva (Fig. 8a) is abundant under the bark of dead henau trees (Eleocarpus dentatus), feeding on the soft inner surface, but leaving the hard wood untouched. In colour it is pale yellow, the head and prothorax are dark brown and corneous, and the remaining segments are provided with two horny warts, from which numerous hairs arise; its legs are all very small, and the caterpillar is considerably attenuated posteriorly; it is very active, wriggling about with great violence when disturbed.
The pupa (Fig. 8b) is enclosed in a compact cocoon, constructed of minute fragments of wood, firmly woven together with silk, and attached to the inner surface of the bark, where it may be soon found by careful searching, and the finest specimens may thus be easily reared in captivity.
The perfect insect appears about November, and may be often observed at rest on the trunks of trees; its pale hind-wings are completely concealed by the dark upper pair, which render its discovery very difficult. The sexes may be at once distinguished by their size, the males being much smaller than the female (Fig. 8) and usually lighter in colour.
CHAPTER VII
The Order Neuroptera, as here considered, is a very limited one, consisting only of the seven small families, which comprise the Lace-wings, Ant-lions, Caddis-flies, and a few others. It forms a most convenient passage from the insects undergoing a complete metamorphosis with a quiescent pupa, to those which are active during the whole of their life, as the larvæ are widely different from the adults, but the pupæ, although incapable of walking or eating, approximate very closely in structure to the perfect insects. I regret that my observations have been at present restricted to three families only, i.e., the Hemerobiidæ, Sialidæ, and Phryganidæ, which will consequently have to represent the entire series. I understand, however, from Mr. A. S. Atkinson, that a species of Myrmeleontidæ (Ant-lion) is not uncommon round Nelson, and doubtless future investigation will reveal insects belonging to the other families.
Family Phryganidæ.
Oxyethira albiceps (?) (McLach.) (Plate [XIV]., fig. 3, 3a larva, 3b pupa).
This insect occurs in the neighbourhood of ponds and streams during the summer. Its larva may be found commonly in the green, slimy weed floating in large masses on all stagnant waters. Being very small it is rather difficult to detect, and is best procured by washing a small quantity of the weed in a saucer of water, when the little insects will be at once seen walking about at the bottom. On examination with the microscope the case will first arrest attention, being of a most unique structure. Its shape is best described as closely resembling that of a minute pocket-flask, very much flattened at the lower end and almost transparent. Its surface is slightly corrugated, and the neck of the flask constructed of a much denser material than the body. It is open at both ends, the posterior end being perforated by a long shallow slit, which extends for nearly the whole width of the case, thus admitting a free circulation of water round the larva, which is also able to turn round and project its head and anterior segments through the lower aperture, thus occupying the reverse position to that shown in the illustration (Fig. 3a). It is, however, prevented from actually leaving the case by its abdomen, which is too large to be withdrawn from either end. The head and thorax of the larva are very horny in comparison with those portions permanently retained in the case, the legs being constructed to fold up into the smallest possible compass, a cavity existing in each joint for the reception of the preceding one—a structure which is almost universal among the caddis-worms. The two organs, situated on the posterior segments, are doubtless respiratory in their function, a large air-tube taking its rise from each and ramifying through the body in all directions. When alarmed these insects retreat into their cases with lightning rapidity, remaining concealed until the danger is passed. Their food probably consists of the green weed, although they are perhaps carnivorous, feeding on the rotifers and other animalculæ, which swarm in the water where they are found.