62 TRANSFORMATIONS OF INSECTS. 
drawn under the posterior margin of the one which immediately 
precedes it. This occurs in all the segments which form the 
abdominal region of the future moth, the nine posterior ones of the 
larva. When the period of changing into the pupa state has 
arrived, a much greater shortening takes place in the muscles of 
the fifth and sixth segments, and in some insects this is carried to 
so great an extent, that the whole body becomes constricted in the 
fifth segment like an hour-glass, and is thus divided into two dis- 
tinct regions—the thorax and abdomen. The same change takes 
place also in the muscles of the first and second segments, by 
means of which the region of the head is divided from that of 
the thorax. The fifth segment becomes almost entirely atrophied, 
and the sixth very much shortened. A part of the fifth segment 
forms a portion of the posterior surface of the thorax of the 
perfect insect, while the remainder constitutes the petiole or neck 
which connects the abdomen with the thorax, the sixth being 
the first true segment of the abdominal region.” 
The engravings of Vanessa urtice (page 41) will assist in the 
comprehension of these changes, as will also the drawing of the 
larva, pupa, and moth of Sphinx ligustri. In this last engraving 
the segments are marked so that the alterations in the three 
phases may be recognised. 
“Exactly the same changes take place in hymenopterous insects, 
and in every other species in which we have had opportunities 
of watching them. It is the opinion of Dr. Ratzeburgh, that the 
head in hymenopterous insects is composed of two segments of 
the larva, because just before the change into the nymph or pupa 
state, a portion of the head is found beneath the integuments of 
the second segment. The fact is indisputable, but the explanation 
of it appears to be this:—The true head of the hymenopterous 
larva consists of but one segment, which is provided with the 
organs of manducation and sensation, the same as in the /e7- 
doptera,; but the head in this larva ceases to become larger 
after a certain period, while the other segments of the body 
continue to grow, and ultimately acquire a diameter more than 
double that of the head. Now the parts which are to form the 
head of the future nymph continue also to grow beneath the 
unyielding cranium, from which, as the change approaches, they 
