New Zealand Entomology/Collecting Insects
CHAPTER II
Collecting Insects.
So many excellent essays have been written on collecting insects that it would probably be a most difficult task to supply much fresh information on the subject; but as many of my readers may be unable to consult works specially devoted thereto, the present chapter will, perhaps, be of some value in showing them a few of the most convenient methods of collecting insects in New Zealand.
Coleoptera, or Beetles, may be found almost everywhere. Overturning logs and stones, peeling off bark, and cutting into the solid wood of trees, all produce a great variety of species. A small axe and an iron wrench, shaped something like a chisel, but bent round at the upper end, are the best instruments for working old trees. The bark should be all stripped off and examined, as well as the surface of the log underneath. The same remarks apply to stones, which should be searched as well as the places from which they were removed. Sacks, if left about the fields for a few weeks, often harbour good beetles, and when found they should always be pulled up and examined.
An umbrella, held upside down under flowering shrubs in the forest, will often be found swarming with beetles after the plants have been sharply tapped with a stout walking-stick. The same object may be attained by spreading a newspaper, or sheet, under the trees and then shaking them; the beetles will fall on to the sheet, and may then be captured. The only advantage of the umbrella is that it can be more readily used in awkward places, such as on steep hill sides.
The dead bodies of birds and animals also contain peculiar species; they may be held over the umbrella and shaken into it, when the inhabitants will fall out, and can easily be obtained. Dead fish on the sea beach are often very productive. Moss and fungi are unfailing resorts of many of the smaller species of Coleoptera, and can be examined in the winter when the entomologist is otherwise idle.
Beetles should always be brought home alive. The small round tin boxes sold with Bryant and May's wax matches will be found very serviceable for this purpose. These boxes are far better for all kinds of collecting than either pill- or chip-boxes, as they do not break when knocked about. A separate box should always be given to a large or rare species, but most of the smaller kinds will travel quite safely in company, especially if a wisp of grass or a leaf is put into the box to give them foothold.
Beetles must be killed with boiling water, and left immersed some hours before setting. They must be pinned through either the right or left elytron, and each collector must always keep to one side, as nothing looks worse than to see some of the specimens pinned on the right and others on the left side. When pinned the beetles are set on a corked board, the legs, &c., being placed in a natural position, and retained until dry by means of pins and pieces of paper and card. The smaller species should be mounted with transparent gum on a neat piece of card, which can be pinned in the store-box or cabinet with the others. The greatest care should be taken to set symmetrically, so that the limbs on the right-hand side of an insect are in the same position as those on the left.
Hymenoptera may be captured with the ordinary butterfly-net, and are found abundantly during the summer. The larger species are pinned through the centre of the thorax, and set in the same way as Coleoptera, the smaller ones on card with gum. These insects should, if possible, be made to fly into the vessel of boiling water, as by this means they generally die with their wings expanded, which is a great assistance when setting them. This can usually be managed by holding the box containing the specimen immediately over the water, and giving it a sharp tap with the finger of the other hand.
Diptera are also captured with the net, and pinned in the same way, but should be killed with the laurel bottle.
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.
The cages I have been in the habit of using are made of two or three thicknesses of cardboard bent round into a cylinder and strongly pasted together. They may be of various sizes, from three to four inches in diameter up to eight or ten, and constructed so that one will go inside the other. The height should exceed the diameter by about one and a half inches. The cylinders should be made so as to stand exactly level on a flat surface, and they should have two rows of small openings round the sides for the admission of air. It is a good plan to have four of these openings in each row and place them opposite one another. They should be covered on the inside with gauze, stiffened with green or brown paint, as the dark colour will enable the observer to see inside more readily. A circular piece of glass is fitted into the upper end of the cylinder, and fixed by means of paste and paper. The base of the cage consists of two round pieces of wood, one about half an inch smaller than the other, the smaller one nailed exactly in the centre of the larger piece. These are made so that the cardboard cylinder fits accurately on the outside of the smaller piece of wood. The whole cage is then neatly covered with white paper inside and brown outside. A complete view of the interior can of course be obtained by looking in at the top, while the cages can be stowed away one within the other when not in use. A stone ink-bottle should be put on the floor of each cage and filled with water, into which a sprig of the food-plant can be introduced. Care must be taken to plug up the mouth of the bottle, so that the larvae may not crawl down the stem of the plant into the water and thus meet with an untimely end. This may readily be done by means of a cork with a hole bored in it for the stem to pass through, or a plug of moss or blotting-paper. Members of almost all the orders can be reared in these cages, as jam-pots full of earth may easily be introduced, in the place of the stone bottle, when required for species which bury. A circular piece of blotting-paper should be placed over the bottom of each cage, while larvæ are feeding in them, and renewed when at all soiled. The excrement must also be removed when the larvæ are supplied with fresh food. As a rule, this is only necessary about twice a week, as the water will keep most plants fresh for quite a lengthened period. When it is necessary to remove a larva it should always be done with a fine camel-hair brush, never with the fingers. Generally, however, it is better to allow the larvæ themselves to crawl from the old sprig on to the new one, which they usually do in a few hours after the food is changed. The old plants should of course then be taken out so as to afford more room for fresh air.
Many female moths may be induced to lay their eggs in captivity, especially if put in a box with some of the food-plant of the larva. It is extremely instructive and interesting to rear an insect from the egg. When the young larvæ first emerge they must be kept in a tumbler with a piece of glass put over the top, as they might escape through the ventilators of the cages, but they ought to be transferred immediately they are large enough. When rearing a lot of caterpillars from a batch of eggs, care should be taken to avoid overcrowding.
A collection of insects should always eventually be placed in a neatly constructed cabinet. They should be arranged in rows, systematically, with the correct names under each species, and the name of the order or group at the commencement of each drawer. Numerous modifications in arrangement are often needed to meet the requirements of different sized insects, but an inspection of any good collection will at once explain the general principles. Camphor should be pinned in the corner of each drawer or store-box, and the whole collection fumigated with carbolic acid, or equal parts of oil of thyme, oil of anise, and spirits of wine, every six months. These can be introduced in a watch glass containing a small quantity of the chemicals on a pellet of cotton-wool, care being taken not to stain the paper at the bottom of the drawer. For the same reason, while using carbolic acid, the camphor should be taken out, as otherwise it will "sweat." All boxes for the reception of insects must of course be lined with cork and paper.
It is most important that an accurate record should be kept of every specimen that is placed in the collection. This may be done by attaching to the pin underneath each insect a small numbered label, which refers to a book containing locality, date of capture and other particulars.
I have found it a good plan to give every species a number, and every specimen a letter. Thus, supposing Vanessa gonerilla is numbered "6," the first specimen taken would be "6a," the second "6b," and so on, all the specimens, perhaps, having different dates and localities. This system is very convenient when specimens are sent away to be identified by another entomologist, as, provided the collector always retains a single specimen of the species which he desires named, it obviates the necessity of having his specimens returned, the number showing at once to what species the name refers. At least five lines should be allotted to each species in the collection journal, and the writing should be small but distinct.
A collection formed in this manner will not only be a constant source of pleasure to the collector and those who succeed him, but very probably of great value in deciding many important questions in entomological science.