CHAPTER VII

_COLLECTING OVA, LARVAE, AND PUPAE_

We have already observed that insects should, as a rule, be set as soon as possible after their capture; and it would therefore seem that this is the proper place for instructions in this part of the work. But it so happens that butterflies and moths are to be obtained by means other than those already described, and we shall therefore consider these previous to the study of the various processes connected with the setting and preserving of our specimens.

Were we to confine our attention to the capture of the perfect forms only, our knowledge of the _Lepidoptera_ would be scanty indeed, for we should then be ignorant of the earlier stages of the creatures' lives, and have no opportunity of witnessing the wonderful transformations through which they have to pass.

Such an imperfect acquaintance with butterflies and moths will, I hope, not satisfy the readers of these pages; so it is intended, in the next two chapters, to give a little assistance to those who would like to know how to set to work at the collection of their eggs and larvae, how to search for the pupae, and how to rear the insects from the stage at which they are acquired till they finally emerge in the perfect form.

These portions of an entomologist's work certainly take up a great deal of his time, and also require much patience and perseverance; but the advantages derived cannot be over-estimated, for in addition to the knowledge gained of the early stages of insect life, this kind of work will enable him to place in his cabinet a number of gems he would otherwise have not and probably know not. Occasionally a prize may be obtained in the form of a cluster of eggs (_ova_) of a rare species, in many instances the larvae are to be obtained with comparative ease, while the perfect insects of the same species are not often seen or not easily captured, and many a rare pupa has been dug out of its hiding place during a season when the entomologist had but little other work to occupy his time.

These and other similar subjects we shall now consider in turn.

_Collecting Ova_

The collection of ova may be carried on more or less throughout the year. A number of moths are out in February, and even in January if the weather is mild. These soon lay their eggs, which are hatched about the time that the buds of the food plant are breaking. From this time till late in the summer the ova of various species are being deposited, the average period from laying to hatching being from two to three weeks. Then, during the autumn, when the leaves of food plants are turning brown and crisp, ova are still being laid, but these remain unchanged till the new buds of the following spring are bursting.

Of course if you intend searching for the ova of particular species you must previously ascertain the favourite haunts of those species, become acquainted with their food plants, and also with the season or seasons during which the eggs are laid. But the few following hints will suffice as general instructions for the search.

In nearly all cases we must expect to find ova on the food plants of the respective species, but at times, especially with certain moths, we may come across them in the most unlikely spots. Thus, it sometimes happens that a moth settles on a street lamp, and lays her eggs on the framework round the glass, or even on the glass itself. The same thing may take place on the sash or glass of a brightly lighted window.

Such occurrences, however, we must regard as accidental and comparatively rare, and therefore we confine our searchings for ova to the food plants of the species we require.

As a rule the under sides of the leaves will yield the most, but we have already noticed (page 18) that some moths leave their eggs exposed on the upper surface. Again, some larvae feed on flowers and seeds and fruit, and the eggs of such are deposited on these parts. Those insects which feed on the leaves of shrubs and trees often lay their eggs on trunks, branches and twigs. Sometimes these are laid singly, sometimes in dense clusters; and it is not unusual to find them arranged in rings or spirals with great regularity. When examining the trunks of trees for ova it is necessary to look well into the crevices of the bark, for some insects take particular care to lay them in deep sheltered chinks; but others take no such precautions, and deposit them on exposed ridges or plain surfaces where they are easily discovered.

One difficulty of the ova collector lies in the fact that many insects lay on the upper branches of large trees. Of course a search for these is out of the question; but in places where the trees have been cut down a few years previously, and where a consequent undergrowth has developed, there are considerable chances of success with these species. Young saplings of trees often yield well, especially in places where tall trees of the same species are absent. It may be mentioned, too, that some moths (page 294) actually lay their eggs beneath the surface of water, depositing them on the under surfaces of floating pond weeds; and others (page 298) even enter the nests of wasps and bees for the same purpose. It is clear, then, from these few remarks, that the work of an ambitious collector of insects' eggs is by no means a monotonous task; for his employment takes him into the meadows and woods, leads him to the banks of ponds, and even compels him to tear down banks and hedges for the nests of _Hymenoptera_ at the risk of a sting or two.

One of the most productive sources of eggs is undoubtedly the possession of captured females. When you are out netting butterflies you often see a female that is evidently engaged in her matronly duties. Instead of seeking food from the various flowers in her path, she pays attention only to the foliage, looking out a suitable leaf on which to deposit her eggs. Should you meet with an insect thus engaged which you would like to rear at home, or of which you would like to know the egg, secure it in a perforated pill box with a leaf of the proper plant; and it will often supply you with abundance of eggs for your purpose, in many cases depositing them in the box before you arrive home. The eggs of numerous species of moths are also to be easily obtained from captured females.

Some insects do not seem inclined to deposit their eggs in captivity as freely as when at large, and in order to induce them to do so we must, as far as possible, put them in their natural conditions. Let them have plenty of room, and supply them with fresh twigs of their food plants, kept green by standing them in vessels of water. It is also advisable, supposing you are not well acquainted with the dispositions of the species you have, to keep a portion of the box well shaded from direct sunlight, and allow another part to be as bright as possible; for some species will not lay in a bright light, while others will not do so without it.

Again, while some deposit their eggs within a few hours of quitting the pupa case, others do not lay for several days. With regard to the latter, it is frequently necessary to feed them while in captivity, by placing in the box a piece of rag or sponge that has been dipped in honey or syrup.

Each batch of ova should be carefully examined with a view to knowing them by sight on a future occasion. A sketch should be made in your note book, showing every detail that you can make out with the aid of a good lens. Then observations concerning the season, colour of the eggs, the situation in which deposited, arrangement, and any other useful particulars, should be entered.

In the next chapter some hints will be given concerning the management of ova and the rearing of the larvae from the time of hatching.

_Collecting Larvae_

This occupation is generally far more productive to the entomologist than searching for ova. The latter are very small, usually well concealed, and to be detected only by a careful scrutinising use of the eyes; but the superior size of the larvae, the frequent bright colouring, and the fact that they are easily beaten from their hold, render the searchings of their hunters comparatively easy and fruitful.

Before setting out on a larva-hunting expedition, there are a few requisites to prepare. These include not only the implements for your work in the field, but also the cages in which you intend to rear your little captives. The latter are described a little later on under the head 'Rearing Lepidoptera,' and the former we will now briefly summarise.

The outfit must consist of a quantity of suitable boxes, a stout hooked stick, a strong net, and a white material to place under the herbage while you are 'beating.'

'Larva boxes' are usually made of zinc, and have little sliding doors in the lids, so that the lids need not be removed while out of doors after the fragment of the required food plant has been inserted. Such boxes are not by any means essential. Small tin boxes will answer all purposes nearly as well, providing a number of small holes be made in them for the admission of air. Chip boxes are also fairly satisfactory, but these also should be perforated. The best way to do this is to push a red-hot iron wire through the chip, making about half a dozen small holes in each box. This method will give you clean holes of a uniform size without otherwise injuring the boxes.

Metal boxes possess the advantage that they keep the food plants moist for a long time, while chip boxes allow them to dry rather rapidly. Yet there are some larvae that do far better in the latter, since such a quantity of moisture exudes through their skins that they soon become uncomfortably wet if their apartment is not well ventilated. Under these circumstances perhaps it is better to take a supply of both, so that changes may be made as found necessary.

One grave objection to chip boxes, however, is the weakness of the material. They are easily crushed by pressure, and a bottom or a top disc of wood often falls out; but this is easily overcome by gluing narrow strips of calico round the top and bottom edges. Chip boxes should always be treated in this way, and they will then last five or six times as long.

Your supply of boxes should always include one large one of metal in which to bring home a supply of food for the larvae. If you have a botanist's vasculum, by all means take it, for nothing can serve this purpose better. If not, any rather large square tin box will do, and this may be carried in your satchel, or a couple of hooks may be soldered to it so that a leather strap can be fixed for slinging it over your shoulder.

The net required is that commonly known as the 'sweep net.' It must be very strong, for it has to submit to rather rough usage. The frame must be made of thick wire; and the bag, which need not be more than a foot deep, should be of strong calico or holland.

Now with regard to the white material previously mentioned. This may be a square of calico, hemmed round the edges. Nothing is more convenient than this, as it occupies but little room in the pocket when not in use, if neatly folded. The material need not be thick, but the larger it is the better. Many prefer a white umbrella or an ordinary umbrella with a white lining, but as this is only a matter of taste and convenience you must decide for yourself as to which you will use.

If your field of operations is only a little way from your head quarters, and quantity of luggage therefore not a serious consideration, you may provide yourself with a heavy mallet, loaded if necessary with a pound or two of lead. This will prove very useful in shaking larvae from trees and large branches. Lastly, take a pencil and a note book or writing paper for your observations in the field.

Now for the choice of the season. Larvae are to be found all the year round. Early in the spring, as soon as the buds are bursting, some break out of the eggs recently laid by the moths that appear in February and March. Later on, during April and May, a host of both butterflies and moths are busy arranging for their broods. Then, throughout the whole of the summer, thousands of caterpillars of all sorts and sizes are to be met with everywhere. And finally, during the bleak winter months, you may amuse yourself by digging the hybernators out of their hiding places where they rest themselves till the spring sun again calls them out to refresh them with the young and tender leaves of a new year. Thus, unless you are merely intending to search out certain species you happen to require, there is not much difficulty in settling on the season.

The day selected should be dry, for your work lies among the herbage of banks, meadows, and woods, and nothing is more unpleasant than wading through a wet and dense vegetation, or beating down on yourself a shower of large drops from the branches of trees and shrubs.

Having reached the hunting ground, the first thing to do is to look out for _signs_ of the presence of larvae rather than for the larvae themselves. Healthy vegetation with sound leaves must be passed by as untenanted; but the presence of partly eaten foliage immediately arouses suspicion.

A little experience will soon enable you to distinguish between the ravages of larvae and of slugs, snails, wasps, &c. Some of the smaller larvae certainly eat out clean holes like those cut by _Hymenopterous_ insects, but as a rule they bite away at the edges, leaving the midrib and the larger veins standing out almost naked.

By looking well into the edges of the eaten leaves, it is easy to see whether the marauders have been recently at work. If they are dried up and discoloured, it is not of much use to search; but if still green and moist, you may feel almost sure that the hungry larvae are not far off.

In this case you will carefully turn over the leaves to examine the under sides, and also the leaf stalks and branches or stems; but you must be prepared for all kinds of protective mimicry. Little green caterpillars will be seen lying on the midrib or veins, so straight and so still that they are scarcely perceptible. Others are snugly tucked in a depression of a leaf with the same result. Then we must also be prepared for the artful little tricks of the larvae of _Geometrae_ (p. 268), by which they imitate stalks and twigs so closely that a sharp eye is necessary to discriminate between the two.

While thus searching we may meet with the cast skin of a caterpillar. This gives us fresh hopes, and so we continue our careful examination. At last, on grasping a leaf in order to turn it over for inspection, we feel something hairy or something soft and smooth. But lo! it is gone. It is one of those numerous caterpillars that feign death and drop to the ground on the slightest sign of danger. We search below for it, but the density of the vegetation renders this hopeless, and we are just about to start off in search of a more productive locality when we espy a quantity of the excrement of larvae lying on a little bare patch of ground close by. This gives us a new idea. Here is another indication of the presence of the creatures we require, one that we can put into practice; and by-and-by we learn that in many cases this is really the surest sign of their whereabouts.

We look at these little pellets of excrement, and gain at once some idea of the _size_ of the larvae that produce them. Then we observe whether they are fresh and moist, or dry and stale. If the latter, it is not of much use to examine the leaves above; but if otherwise, there is little doubt of our meeting with larvae, as the present position they occupy is so truly marked. The leaves just over them are carefully examined, either by turning them over as before described, or, if the height of the foliage admits of it, by placing our heads below and looking upward.

If we find that the larvae are some of those that endeavour to escape by feigning death and allowing themselves to drop at the slightest disturbance, the net is always kept beneath the leaves we are touching in order to intercept them in their downward journey.

Continuing the search, we meet with leaves that are rolled up and bound with silk threads, and others that are drawn together and similarly bound. These are carefully uncurled and pulled asunder with the result that active little larvae are exposed to view, or, it may be, pupae are discovered. In some cases flowers are drawn together in just the same way, and an examination reveals one or more of the species that prefer petals and other parts of flowers to the green leaves.

Silken threads always arouse our suspicions. These may be seen lying on the surfaces of leaves, and passing from one leaf to another, or they may be hanging perpendicularly from the branches of trees above. In the latter case a larva may be frequently seen on the lower extremity of the fibre, swinging gently in the breeze, and, should we require it, we have only to place the open box below for its reception.

Hawthorn and other trees are sometimes seen almost devoid of leaves, nearly every bit of green having been greedily devoured by a host of small larvae. In such cases we often meet with dense clusters of silk fibres that may easily be mistaken for spiders' nests. But when we look more closely into the structure we observe that we have discovered instead nests of gregarious larvae, such a large number being in each little community that the deplorable appearance of the tree is at once explained.

A little farther on we meet with a sickly-looking plant in the midst of a number of flourishing individuals of the same species, and stop to make inquiries into the cause of this strange occurrence. Is it due to a poorness of the soil? No, this cannot be the case; for intermingled with its roots are those of its flourishing companions. We pluck a stunted and half-shrivelled leaf and examine it. At first we do not notice the cause of its peculiar condition; but, holding it up to the light, and looking _through_ it, we see a number of little galleries that have been eaten out of its internal soft substance, leaving the thin skin (_epidermis_) almost entirely intact. But nothing more is to be seen. Another leaf is examined in exactly the same way; and here we see the little destroyer, lying motionless in its burrow till a gentle pressure applied against it from outside causes it to wriggle along its narrow passage. This is the larva of one of the little leaf miners mentioned again on page 303.

Reaching a little marshy spot we see a number of water-loving reeds, most of them beautifully green and in a flourishing condition, but here and there in their midst is a poor stunted specimen--another result of the ravages of the larvae of one or more moths. An examination of the blades reveals nothing; but on splitting open the stalk we discover some larvae that have already devoured a quantity of the internal pith, and thus endangered the life of the plant. On inspecting other similar reeds we are at first puzzled as to how the larvae could get inside the stems without damaging the outer portion; but at last we see in each one a little discoloured hole that was eaten out by the young caterpillar just after its escape from the egg. Once within the reed, it found a plentiful supply of food, and there grew at the expense of the plant without doing any further external damage save by causing a stunted growth.

It may be that the stem eaters we have found are just about full grown. If so we examine a number of the stems with a hope that we may find one or two that are just about to change to the chrysalis state, or even a pupa already formed. By this means we may secure one of the perfect insects without the necessity of feeding larvae at home. Such a consideration becomes a most important one when it happens that the required food plant is one that cannot be easily obtained.

Close by the reeds is another water-loving plant in the form of an old willow tree. This is always an attractive object to the entomologist, so it comes in for a share of our inspection. On its leaves we may find several species of the larvae of _Lepidoptera_, including those of some of our largest insects. But a strange feature catches our eyes as we happen to glance at the bark of the tree. Here we see a few holes of different sizes, about which are a number of little fragments of wood that remind us of 'sawdust;' and, examining the ground below, we see quite a little heap of this dust, looking just as if a carpenter had been at work on the spot.

This is not the effect of a saw, however; it is a sure sign of the ravages of wood-eating larvae (p. 224), whose powerful jaws gain them admittance into the very hearts of trees, and the application of the nose to one of the larger holes leaves no doubt of the presence of the large and beautiful caterpillar of the Goat Moth (p. 224).

If we require any of these wood-eaters, either for rearing or for preservation, we must be prepared for a little rather heavy work. A strong pocket knife is not sufficient, but with a good chisel the wood can be gradually cut away, and the galleries traced, till at last we come to the larvae snugly resting in their burrows.

It often happens that the tree thus tenanted is half decayed, and consequently the work is rendered much easier. Also, while tearing away the wood, we often meet with a number of cocoons that have been constructed by the caterpillars for their winter quarters, or as a resting place while undergoing their transformations. These are composed of the wood dust bound together by strong silk fibres, and are often in such a good state of preservation that they form useful illustrations for the cabinet.

As further aids to larvae searching we may mention that many species--chiefly of the _Noctuae_--hide under the surface of the ground or among dense and low herbage during the day, and come out to feed only by night; that many others feed on roots, and are therefore seldom seen above the surface of the soil; also that a good number burrow into fruits, in the interior of which they spend the whole of their larval stage. The best way to secure the latter is to examine the 'windfalls' that lie scattered on orchard lands, for it is a well-known fact that the fruits that are infested with larvae generally fall earlier than others--a result that must be attributed to the damaging work of the larvae themselves.

All the larvae collected should be carefully boxed at once, a separate compartment being used for each species, and a few fragments of the food plant being introduced in each case. It is also a good plan to have each box previously lined with moss as a further addition to the comfort of the captives. Without such a precaution some of the more delicate species are liable to injury during their transmission from field to home.

Hitherto we have obtained our larvae by _searching_ only, but there are times and occasions when our boxes may be far more rapidly filled by methods that are not such a tax on our time and patience. Suppose, for instance, that we reach a bush, the mutilated leaves of which seem to show that larvae are present on its branches. We spread our white cloth or open out the white-lined umbrella just under a selected branch, and then tap that branch very smartly with our stick.

Down comes a host of living creatures! Spiders, larvae, beetles, aphides, earwigs, and what not, struggling and running about on our white fabric in all directions, and all mingled with bits of stick, leaves, and fragments of all kinds. We leave the cloth or the umbrella, as the case may be, quite still for a few seconds to allow all the living creatures to get a good foothold, and then, raising it into a vertical position, allow all the rubbish to drop off.

We can now put the cloth down again, and select as many of the larvae as we require, giving our first attention to the nimble runners and loopers that are already near the edge and just on the point of making their escape. This productive method of larva hunting is known as 'beating,' and is particularly applicable to tall herbs and the lower branches of trees and shrubs.

The same principle may be employed in the case of branches that are quite out of the reach of the stick, but the blows are here applied to the trunk, a mallet or some other rather heavy implement taking the place of the stick.

Another splendid method of securing larvae where mere searching would be tedious and unproductive, lies in the use of the sweep net described on page 102. This implement comes into service in waste places that are covered with rank vegetation, in clover and hayfields, and in all spots covered with low herbs.

Walking among the vegetation, the net is swept right and left before you, and the contents examined at frequent intervals. It is advisable to work the different species of herbs separately as far as possible, otherwise there may be some difficulty in the determination of the food plants of the mixed larvae that the net will contain. If, however, this plan is impracticable, you may save time by turning out all the 'sweepings' into one large box, leaving the sorting to be done at home in leisure hours.

_Collecting Pupae_

We have seen that ova and larvae may be obtained in greater or less abundance at all times of the year, so variable are the seasons of the different butterflies and moths. The same remark applies equally well to pupae; but so many of the Lepidoptera spend the winter months in the chrysalis state that this period may be regarded as the harvest time of the pupa hunter.

A large number of caterpillars undergo their change to the quiescent state during the months of August and September, and, of course, remain in this state until the warm days of the following spring or summer. And as insects even in the pupal stage have a number of enemies and dangers to contend with, it is advisable to start your search for them as soon as possible after they have changed.

If you set your mind on searching for particular species, you should endeavour to ascertain the _usual_ time at which such species pupate; make any necessary allowances for the forwardness or backwardness of the season, and then allow a week or two for the change to be completed, for insects should never be disturbed at times when their metamorphoses are in progress.

For general pupa hunting the best season is undoubtedly from the end of August to the end of October, but there is no reason why the work should not be carried on throughout the winter. If, however, you continue your work so late, you must not expect nearly as much success as time advances. You must remember that entomologists are not the only pupa hunters. Many hungry birds are always on the look-out for insects, and seem to enjoy them equally well in all their stages. Those that hybernate on or under the ground are liable to fall a prey to moles and beetles. In addition to these dangers, all pupae are subject to the effects of extreme cold, dampness, or floods.

As regards the choice of a day, very little need be said. Any day that is sufficiently genial for yourself will do for your work, except that periods of hard frost render the ground too hard for digging--the most profitable part of the pupa hunter's task.

The apparatus required is extremely simple: A satchel or large pockets full of small metal or chip boxes, a small garden trowel, and a strong chisel.

If metal boxes are used they should be perforated; in fact, nothing is better than the ordinary larva boxes of the dealers. All the boxes, of whatever kind, should be lined with moss previous to starting work.

The trowel and chisel do not pack well with a number of small boxes, therefore it is a good plan to fix them in a couple of leather sheaths attached to your belt. In this position they are far more handy for use, and the boxes are also in less danger of being crushed or damaged, as they probably would be if in contact with hard and heavy tools.

A note book is also a valuable addition to your outfit, as it enables you to make memoranda concerning the trees and localities from which you obtain your pupae.

The best localities for pupa hunting are clearings in woods, parks with numerous large timber trees, and meadows in which large isolated trees are scattered; and the best trees include willows, poplars, oaks, beeches, birches, elms, and hawthorns.

The best thing you can do on arriving at the selected hunting ground is to make at once for isolated trees of large size, and work each one as follows:

First examine well the crevices of the bark, for many caterpillars descend the tree to within a short distance of the ground, and then seek out a snug little crevice in which to spend the winter, often protecting themselves with silken cocoons, or constructing a neat little shelter of gnawed fragments of the wood cemented together.

If there is any loose bark, very carefully force it out with your chisel, and examine both its inner surface and the wood from which it was removed. The wood thus exposed may reveal openings of the galleries of wood-eating larvae, in which case, unless the material is too hard to be broken up with the chisel, you may be able to trace out a few pupae. Where these exist, they are usually to be found very near the entrance, sometimes even protruding slightly from the opening, for the larvae generally place themselves in this position of easy escape when about to change.

Next give your attention to the moss, if any, covering the lower portion of the trunk. This affords a very favourite shelter to many species. Tear it off very carefully, beginning at the top, and watch for loose pupae and cocoons as you do so. Then hold the clumps you have removed over a patch of bare ground or over a spread handkerchief, and pull it to pieces, in order that any pupae it contains may fall out; also examine the fragments carefully for others that may remain attached.

This done, the surface of the ground must be examined. Remove all dead leaves, and watch for pupae that may be sheltered beneath them. If any loose stones lie on the ground, turn them over. Search well into the angles between the roots, and if there are any holes or hollows beneath them or in the trunk itself, pull out all loose matter within, and _feel_ gently above and around for cocoons.

After all loose matter has been removed, there still remains the soil for examination. If this is very hard and clayey, it is probably useless to carry the search any farther; also if very wet you need not expect much; but if comparatively dry and friable there are more hopes of success.

As a general rule the north and east sides of the trunk are drier than those which are exposed to the heavy rains brought by the south and south-west winds, and are consequently more favoured by larvae that are seeking a resting place for the winter.

Most larvae seek shelter in the angles between the roots of the trees on which they fed, but a few species seem to prefer the edges rather than the corners; and in cases where no such angles are formed at the surface, you will do well to examine the earth and turf all round the trunk; but it is generally useless to extend the search more than a few inches from the tree.

After having searched every available nook and corner as far as possible without digging, thrust the trowel obliquely into the soil a few inches from the tree, turn over the sod, and then examine the spot from which it was removed. Now give your attention to the sod itself. If loose and friable, break it up gently, keeping a sharp eye for falling pupae, and also for earthen cocoons that are easily mistaken for little lumps of soil.

If the soil is held together by roots, it must be pulled to pieces, and the fragments shaken over a bare piece of ground where the fall of a pupa or cocoon could be easily seen; and if you have removed a grassy turf, it will be necessary to look between the bases of the blades as well as among the roots.

In this way you may search round tree after tree, wherever the soil is of such a character as to allow of the admittance and shelter of larvae. But the variability of your success will be quite beyond your comprehension. Sometimes you will sight a grand old oak with the most favourable anticipations, and consider yourself quite certain of a good find when you discover, on a nearer approach, the liberal coating of moss that clothes its trunk and the dry sandy soil at its foot; and yet the most careful search ends in nothing but disappointment. At other times you try your luck at tree after tree without ever seeing a single pupa or even a cast-off case, and then, when just on the point of despairing, you search round another that is apparently much less promising, and, to your great surprise and delight, a dozen or two are turned out in a few minutes. Such an occurrence as this is not at all uncommon, and cannot be satisfactorily explained, but we must take things as they come and make the best of them, remembering that pupa searching is one of the best of all entomological operations wherewith to test one's perseverance and patience.

It may be mentioned, in conclusion, that the pupae of _Lepidoptera_ are never to be found far below the surface of the soil. Generally they exist, if buried at all, only an inch or two down, and very rarely at a greater depth than four inches.

In our next chapter we shall learn how to rear the perfect insects from the earlier stages we have been considering.