OF THE LARVA OF PYGÆRA BUCEPHALA. . 189 
to give up this task, and do not think that it can be effectually accomplished until we 
know the arrangement which exists in some of the intermediate genera. 
Some, however, of the more remarkable peculiarities of the thoracic segments in 
Pygæra are equally present in Cossus. Thus, the altered position of 1, 8, 8', 18, 22 and 
82 resemble those of D, C and E, c and e and C+. The remarkable muscles, however, 
marked 76 and 77, do not appear to have any close representative in Cossus. 
This comparison, however, is made far more difficult by the arrangement of Lyonet's 
figures, and by the fact that the same letters are certainly not always used for the corre- 
sponding muscles in different segments. 
In the first abdominal segment of the larva of Pontia rapi the larger muscles were 
arranged nearly as in Pygæra, except that 2 was attached to the skin at the posterior end 
of the segment, as in the larva of Cossus. In the larva of Disphragis ceruleocephala the 
muscles 1 and 2 on the one hand, and 16, 17 and 18 on the other, were represented by 
numerous separate fascicles, amounting to at least ten in each instance. 
This separation of the fibres composing a muscle into separate fascicles is carried to a 
much greater extent in the larvæ of Coleoptera, or at least in Dyticus and the wood-feed- 
ing Lamellicorns, which alone I have examined. In these two groups each of the larger 
muscles is represented by at least twenty separate fascicles, which makes it far more 
diffieult to distinguish the arrangement of the muscles. 
The reserves of fat in the larvæ of these Lamellicorns are stored up in large vesicles, as 
much as ‘01 of an inch in diameter, and which, being connected together into thin mem- 
branes, like a mesentery, have a beautiful bead-like appearance to the naked eye. 
The muscular system of the larva of Tipula oleracea and of Ctenophora bimaculata* offers 
us many interesting points of difference. Being unprovided with legs, these little creatures 
move by resting one part of their body against some solid object, and then pushing the 
anterior part forwards. To enable them to do this with facility, an immense number 
of muscles are attached to the inner side of the skin. The total number, indeed, falls 
a little, though very little, short of that in Cossus; yet the real complexity is greater, 
since the average number of muscles in each of the body-segments is rather over m enty 
in Tipula, while in Cossus it is about sixty. This surely shows greater complexity than 
the larger total, which is merely made up by the irrelative repetition of a lesser number 
of muscles in a greater number of segments. 
The joints of the back in the larva of Cossus, like those of Pygæra, allow | 
play than those of the ventral side, and we find the muscles entirely in accordance with 
this structure. On the contrary, in the larva of Tipula and of Ctenophora bimaculata, 
the back can be bent almost, if not quite, as much as the belly; and if this were not already 
known, it might be deduced from the arrangement of the muscles. 
Lyonet remarks (p. 154, 7. c.) that his “a,” which corresponds to my 2 adr) 
quable, en ce que, pendant que les autres muscles droits se terminent aux some pes 
anneaux, son extrémité postérieure passe au 4, 5, 6, 7, 8, et 9 anneaux cette L 
*t s'insère assez avant dans l'anneau qui suit; ce qui vraisemblablement a été ain 
much less 
1, “est remar- 
i d found with, those 
: Mr. Walker was kind enough to name for me specimens bred from larvæ resembling, an 
Which I dissected, = 
Cc 
