: 
32 . : NA TURE 
The egg is soon hatched in each chamber, anda small, legless, 
and extremely delicatelarva crawls forth, and seizesuponthe victim | 
close to it. So tender is the Jarva that the least roughness of the 
sides of the chamber would destroy it, and the least struggle on 
the part of the poisoned weevil grubs would kill it; but all this 
has been made safe, and the little thing eats into its living prey, 
and when one is finished it attacks another, until all are eaten 
up. This is the life of the larva, It is incapable of walking any 
distance, and simply leads a life of gormandising on the flesh and 
juices of weevil grubs, It never emerges from the chamber, and 
when it has no more to eat, spins a cocoon of silk around itself, 
and sleeps therein during the late autumn, the winter, and until 
the spring, Then a change in form ensues, and a pupa, which 
greatly resembles the perfect insect, appears under the skin 
which is shed. In the course of a few weeks the perfect false 
wasp escapes from the pupa skin, digs its way into the world, 
and emerges to enjoy the destiny already described. 
Many other false wasps which belong to the same group of 
insects as this Odynerus have a somewhat corresponding life 
cycle, and choose many curious kinds of prey, but the formation 
of the safeguard of {the tubular ante-chamber places this kind in 
advance of all others. It is then an example of very perfect 
metamorphosis with high instinct, and, like in all other instances 
of what is termed perfect metamorphosis, there is an intermediate 
stage of a quiescent pupa between that of the larva and imago, 
both of which are able to lead independent and distinct kinds of 
lives, and to take food. 
Considered as isolated examples, these two instances of 
metamorphosis are perfectly inexplicable, except on the theory 
that the successive changes—shape, structure, and habit— 
were especially given to the species at their origin, by special 
creation. When, however, the nature of the very different 
metamorphoses of other insects, which closely resemble these 
in structure, is examined into, this view does not give entire 
satisfaction, and an uncomfortable feeling arises, that we with 
finite understandings are tying down the operations and myste- 
rious ways of Omnipotence to our own limited standard. 
But before proceeding any further, it is necessary that the 
nature of some of the structural alterations which occur during 
metamorphosis should be stated. By so doing a distinction can 
be appreciated between ordinary continuous growth or progres- 
sive development, and the changes which occur during the per- 
fect metamorphosis of an insect. Consider shortly the nature of 
the change of outside form. A young larva of a butterfly or 
moth has a head which is not separated by a neck from the long 
body, and the whole is divided more or less distinctly into rings 
or segments. The three segments next to the head form the 
chest and support the true legs, and are succeeded by nine others 
belonging to the body or abdomen, There are then thirteen in 
all, The body segments are nearly equal, but the last is the 
smallest, and it, together with some of the other rings, supports 
what are termed false legs or claspers. They are continuations 
of the skin, and do not exist in all larvz of butterflies and moths ; 
and, although they are extremely useful in enabling the insect to 
hold on and to crawl, they disappear in the pupa state with the 
last skin-shedding. Thus there is the head segment, and three 
chest segments, and nine body segments, and on the side of each 
of these, excepting the head, is a point, which usually marks an 
opening where air tubes or trachez enter the body to ramify over 
the whole of the internal structures. When within the egg, and 
before it was perfectly formed, the head of the larva consisted of 
at least four separate pieces, but these united and coalesced in 
one before birth. None were destroyed, but the edges of the 
separate portions fused together. A corresponding fusion and 
blending of certain of the chest and body segments occurs during 
metamorphosis, and there is neither a destruction nor new crea- 
tion of parts to produce the extraordinary difference between 
the long body of a caterpillar, the short swathed figure of the 
pupa, and the great chest and small abdomen of the butterfly. 
The same anatomical elements are present, but they are more or 
less modified, 
The first skin sheddings of the caterpillar do not add 
to or alter its segments, but the last skin shedding which 
occurs during a period of immense internal change exposes the 
pupa or chrysalis to view, and all the characteristics of the skin 
of the larva are lost. On commencing this last skin shedding, 
the chest segments, 2, 3, and 4 (Fig. 1) of the caterpillar, increase 
in size, and the insect really soon begins to shorten. The small 
Tortoise-shell butterfly larva is thus suspended, with its skin on, 
for some ten or twenty hours before the chrysalis is revealed. 
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(Nov. 14, 187 
During this time, the 2, 3, 4, and 5 segments become much en- | 
larged and curved downwards by the action of the muscles of 7) 
their under surface, which are repeatedly contracted and ex- | 
panded slowly. The skin bursts, and the insect then exerts it- | 
) 
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iy 
self to the utmost to extend the fissure along the segments of 
body, and gradually draws out its antennz, or feelers, and 
weak but long legs, and immature“wings, all of which have been 
maturing beneath the old skin, and are covered with an ex- 
tremely delicate tissue. The false legs drop off with the old 
skin, and the pupa hangs in this moist and curious condition for 
a few minutes. Then it makes a few powerful efforts, and con- » 
tracts and expands itself to the utmost by taking in air through 
its air tubes and forcing it out again by bringing the segments 
closer together. The result is to contract the body segments 
along their under surface, and to diminish their length generally. 
The front margin of one segment is drawn up within the hinder — 
edge of the one in front, and especially in the case of the fifth and 
sixth segments. ‘his contraction persists, and in the neighbour- 
hood of the fifth is sufficient to initiate the small waist-like circular 7 
division between the chest and the body, which becomes more dis- 
tinct in the imago than in the pupa. Atrophy and shortening — 
of the fifth and sixth segments occur ; and there are correspond- — 
ing changes in the first and second segments, so as to commence 
aneck. A gelatinous viscid fluid is secreted by the pupa, and it 
covers all its delicate external skin, and by hardening aggluti- — 
nates all beneath. After a while the true skin of the pupa, is 
found separated by air from the dark pupa case outside, : 
After the escape of the imago from the pupa case, if its wings be 
removed, and its head, chest, and body be examined, thedistinction — 
between the number of its segments and those of the full-grown — 
larva will be readily appreciated. The nine body-rings of the — 
caterpillar exist, but are much modified. The two terminal are 
drawn up inside the body, and the first segment has joined itself — 
to the last chest-piece. The shortening is very great, whilst the 
enlargement of the rings which support the wings—namely, the — 
third and fourth—with much consolidation and fusion of them, 
does not compensate for it. As may be supposed, the shortening 
of the internal organs must be extraordinary, and as a matter of — 
fact the nervous cord is shortened, its ganglia are concentrated, 
and the digestive apparatus is diminished in length in a remark- 
able manner. q 
The changes{in the digestive organs keep pace with those — 
of the skin and general shape, and may be briefly described — 
as follows:—When a caterpillar nips off a piece of a leaf 
with its jaws, the morsel is passed into the gullet, which is a 
short tube leading to the stomach. The gullet is composed of a — 
mucous coat which is internal, and of a muscular covering which — 
is external. The mucous coat consists of a delicate structure- — 
less membrane, which is continuous with a corresponding tissue — 
in the mouth in front and in the stomach behind. It is called — 
the basement membrane, and that of the gullet is folded longways, 
when it isempty. When the gullet is crammed with food, the 
folds are obliterated and the membrane is stretched. All the in- — 
side of this membrane is covered with a layer of delicate hex- 
agonal cells, which are very small and thin, and consist of a plain — 
cell wall and transparent fluid contents (Fig. 2). ‘They coverthe — 
basement tissue like a pavement, and the morsel of food comes in — 
contact with them, and they absorb and transmit any vegetable — 
liquids which may escape from the cells of the leaf. Between 
the hexagonal pavement cells here and there are oval depressions 
filled with granular mucus. The basement tissue is slightly de- 
pressed in these spots, and these crypts secrete a fluid whichacts 
like the salivary glands of man upon starchy and sugary fluids. 
Amongst the hexagonal cells are others which have their upper 
surface produced into a short tooth-like projection, that fore- 
shadows a remarkable structure in the perfect insect. Outside 
the basement membrane is a single row of hoop-shaped muscular 
fibres. They are broad and nucleated, but not striated. Each 
fibre encircles the gullet, and tends, with the simultaneous con- 
traction of its fellows, to diminish the calibre of the tube, and 
to throw it into longitudinal folds, Their passive dilatation, on 
the contrary, permits the gullet to become distended. They 
haye, however, the peculiarity socommon in the circular muscular — 
fibres of all animals, of contracting one after the other in series, — 
and of dilating or expanding in the same rhythmical manner. The _ 
result of this progressive contraction is to force the contents of — 
the gullet in the direction of the stomach. The alterations of 
contraction and the expansion permit the layer of muscular fibres, 
which is outside the circular set, and whose direction is longitu- 
dinal, to pull up and shorten the canal, The long fibresare 
