_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.