Lepidoptera are the most difficult of all to collect, and are at the same time the most attractive to beginners. They may be captured with a net made of fine gauze (mosquito net dyed green is the best material); the frame to support the net is constructed of a piece of cane bent into a hoop, each of the ends being supported in a forked tube shaped like a Y, and the long tube, forming the base of the Y, is firmly fitted on to the end of a walking-stick. This form of net is light, strong, and easily made; the only thing requiring special attention is the Y, but this can be readily made by any tinsmith out of two pieces of gas-pipe of different sizes, the larger one for the stick, and the smaller one for the ends of the cane to fit into. The collector should also be furnished with a number of small tin boxes.[[1]] All this apparatus can easily be packed into an ordinary satchel.
When the entomologist reaches his hunting-ground, he will mount his net and place a number of the boxes in his left-hand coat pocket. The foliage of all trees and shrubs should be vigorously beaten and the insects captured as they fly out. When a moth is taken, the collector will first turn the net half way round so as to close the entrance, and then, directly the insect ceases fluttering, he should carefully place one of the little boxes over it and slip on the lid. The box is then transferred to the right-hand pocket. He will soon learn to do this without in any way damaging the insect. On arrival at home, the insects should be immediately killed in the laurel bottle. This is an ordinary wide-necked bottle with a small bag of well-bruised young laurel shoots at the bottom, covered with a circular piece of card fitting accurately to the sides of the bottle. Laurel shoots can always be obtained about the middle of October, when several killing bottles can be prepared. They must always be wiped out before using, and kept carefully corked. After a few hours the insects should be tilted out of the bottle on to a tablecloth, and pinned exactly through the centre of the thorax. The rough surface of the tablecloth prevents them from slipping during the operation. About one-third of an inch of pin should project below the body of the insect. If a moth or butterfly dies with its wings folded upwards over the back, it must be carefully picked up between the thumb and index finger of the left hand, and the pin inserted with the corresponding fingers of the right hand. When all are pinned they should be transferred to a tin box, lined with cork, which has been previously well damped with water. While pinning them into this box great care must be taken not to allow the wings to come in contact with the damp cork. In about twenty-four hours the specimens thus treated will be ready for setting. This process is performed by means of corked boards of various widths for different sized species. Each board has a groove down the centre for the bodies of the insects to rest in, while the wings are spread out on either side. They should be carefully moved forwards with a fine-pointed needle to the desired position, and retained by strips of tracing cloth pinned firmly down at the ends. These strips must not be removed until the insects are thoroughly dry and ready to place in the store-box or cabinet. In setting Lepidoptera, as with other insects, symmetry and a natural position are the main points to be aimed at, special care being taken that the antennæ, fore- and hind-legs, and wings, are shown in correct positions, the middle pair of legs being of course, in the majority of cases, hidden by the wings. It is almost needless to say that different sized pins should be used for various insects, but this point must be left to the discretion of the collector. Entomological pins of all sizes can be obtained from James Gardner, of 29 Oxford Street, London. Gilt pins are useful for many species which are liable to form verdigris on the pins, and are universally employed by many entomologists, but are probably not so strong as the silvered ones.
Many species of moths are only to be found at night. When working at this time the collector must suspend a bulls-eye lantern round his neck or waist, and can then have both arms free for capturing insects on the wing or at blossoms. Honey mixed with a little rum, and applied with a small brush to the trunks of trees a few minutes after sunset, will, on some evenings, attract large numbers of valuable species, but not infrequently it is quite unproductive. This mode of collecting has been termed "sugaring" by entomologists, and may be employed during the whole summer. The best blossoms for attracting insects in New Zealand are those of the white rata,[[2]] which blooms in the forest from February till April, and from which the collector may generally rely on getting a rich harvest. The insects can usually be slipped directly from the flowers into the killing bottle.
This is much better than netting them, although occasionally one will escape during the process. When dead the specimens should be placed in a small tin box which has been filled with cotton-wool, packed very lightly. In this way a large number of moths may be carried a long distance with perfect safety, and the extremely inconvenient process of pinning them in the field obviated. If Jahncke's patent boxes are employed it is quite unnecessary to kill the moths in the field. They can be boxed directly from the blossoms and taken home alive without suffering any injury.
Lepidoptera, and in fact all insects, are attracted by light, and in some situations the collector will find that he may frequently obtain good species by merely opening his sitting-room window and waiting for the insects to arrive. Much of course depends on the situation of the collector's residence and the nature of the night, which should be dark and warm. I have occasionally tried taking a lamp into the forest to attract insects, but have not met with much success. In swampy and flat situations, no doubt, attracting by light would be very effective, especially if a powerful lamp was employed, in an exposed situation, with a sheet behind it, supported between two poles. This method has been followed with great success by many English entomologists in the fens, but has not yet been tried in the New Zealand swamps, where it would probably be the means of bringing many new and interesting species to "light."
With regard to collecting members of the three remaining Orders but little need be said. Neuroptera can be treated in the same way as Lepidoptera, but they should be set on flat boards. The treatment of the Orthoptera will resemble that of the Coleoptera, but the larger species will require to be stuffed with cotton-wool before setting. A few of the largest species of the Lepidoptera must also be stuffed. For this purpose the specimens should be placed on their backs on a piece of clean glass so that none of the scales may be rubbed off. After the contents have been removed, a little chalk should be introduced into the abdomen with the cotton-wool. Hemiptera can be collected and set like Coleoptera, but some of the more delicate species, such as the Cicadæ, should be killed in the laurel bottle instead of in boiling water.
Before concluding the present chapter I should like to say a few words on the subject of rearing insects, which the entomologist will soon learn to regard as by far the most interesting method of acquiring specimens for his collection.
Members of the Coleoptera are probably the most difficult insects to rear in captivity. Their larvæ may be kept in ordinary jam-pots covered with perforated zinc, and filled with earth or rotten wood. The carnivorous species must, of course, be supplied with the animals on which they feed. Beetle larvæ are often some years in attaining maturity. Many of the Hymenoptera and some of the Diptera are parasitic on the larvæ of the Lepidoptera; they are consequently found in rearing these insects, and their economy should always be carefully recorded.
Lepidoptera are, perhaps, the most satisfactory insects to rear. Most of the larvæ feed on the leaves of different plants, and all that is needed is to keep them well supplied with fresh food.
So great a variety of cages have been devised for the rearing of caterpillars that it would be quite impossible to describe them here. I will therefore only give a short account of those which I have used myself, and have found so convenient that I do not hesitate in recommending them to those entomologists who wish not only to rear insects but to study their habits.