NATURE 
31 
a INSECTS * 
ON THE ORIGIN AND METAMORPHOSES OF 
i, Ill. 
. THE INFLUENCE OF EXTERNAL CONDITIONS ON THE 
ji FORM AND STRUCTURE OF LARV 
| liens facts recapitulated very briefly in the preceding 
chapters show, that the forms of insect larva depend 
greatly on the group to which they belong. Thus the 
same tree may harbour larve of Diptera, Hymenoptera, 
Coleoptera, and Lepidoptera ; each presenting the form 
typical of the group to which it belongs, 
Fic. 1, Larva_of_the Cockchafer (Melolontha). (Westwood. Int. to the 
M Classification of Insects, v- z., p. 194.) 2, Larva of Cetonia, 3, 
Larvaof Trox. 4, Larvaof Oryctes. 5, Larva of Aphodius. (Chapuis 
and Candeze, Mem. Soc. Roy. Liege, 1853. 6, Larva of Lucanus. 
(Packard, ‘‘ Guide to the Study ot Insects,” Fig. 403). 
If, again, we take a group, such, for instance, as the 
Lamellicorn beetles, we shall find larve extremely similar 
in form, yet very different in habits. Those for instance 
of the common cockchafer (Fig. 1) feed on the roots of 
grass, those of Cetonia aurata (Fig. 2) are found in ants’ 
nests ; the larvz of the genus Trox (Fig. 3) on dry animal 
substances ; of Oryctes (Fig. 4) in tan-pits : of Aphodius 
Fig. 5) in dung; of Lucanus (the stag-beetle, Fig. 6) in 
w 
- 
‘Fic. 9, Larva of Sitaris humeralis. 
(Fabre, Ann. d. Sci. Nat. Ser. 
4, vol. vii.) rva of Sitaris humeralis. in the second stage. 
31, Larva of Sitaris humeralis, in the third stage. 12, Larva of Sitaris 
humeralis, in the fourth stage. 13, Pupa of Sitaris. 
10, 
Tm the -present chapter it will be my object to show 
that the form of the larva depends also very much on its 
mode of ‘life. Thus, those larve which are internal 
parasites, whether in animals or plants, belong to the 
vermiform state ; and the same is the case with those 
which live in cells, and depend on their parents for 
food. On the other hand, larve which burrow in 
* Continued from yol. vii. p. 489. 
wood have strong jaws and generally somewhat weak 
thoracic legs ; those which feed on leaves have the 
thoracic legs more developed, but less so than the carni- 
vorous species. Now, the Hymenoptera, as a general rule, 
belong to the first category: the larve of the Ichneu- 
mons, &c., which live in animals,—those of the Cynipida, 
which inhabit galls,—and those of ants, bees, wasps, &c., 
which are fed by their parents, are all fleshy, apodal 
grubs. On the other hand, the larvae of Szvex, which are 
wood-butrowers, quit the type which is common to the 
majority of the order, and remain in the egg until they 
have developed small thoracic legs. Again, the larvze 
of the Tenthredinidz, which feed upon leaves, closely 
; 
Fic. 7, Larva of Brachytarsus (Ratzeburg, Forst. Insecten). 8, Larva of 
Crioceris (Westwood, l.c.) 14, Larva of Sirex (Westwood le.) 15, 
Egg of Rhynchites, showing the parasitic larva in the interior. 16, 
the parasitic larva more magnified. 
resemble the caterpillars of Lepidoptera, even to the 
presence of abdominal prolegs. There is, however, some 
little variety in this respect, some species having eleven 
pairs, some ten, some nine, while the genus Lyda has only 
the three thoracic pairs. 
Again, the larvze of beetles are generally active, hexapod, 
and more or less flattened: but on the other hand with 
those species which live inside vegetable tissues, such as 
the weevils, they are apod fleshy grubs, like those of 
Hymenoptera. Pl. 2, Fig. 6, represents the larva of 
Fic. 17, Egg of Platygaster (after Ganin). 18, Egg of Platygaster 
‘Hiscineahe central ate 19, Egg of Platygaster after the division of 
20, Egg of Platygaster more advanced. 21, Egg of 
the central wall ; D 
22, Egg of Platygaster showing the rudi- 
Platygaster more advanced. 
ment of the embryo. 
the nut-weevil, Balaninus (Pl. 1, Fig. 6), and it will be 
seen that it closely resembles Pl. 2, Fig. 5, which represents 
that of a fly (Anthrax), Pl. 1, Fig. 5, and Pl. 2, Figs. 7, 8, 
and 9, which represent respectively those of a Cynips or 
gall-fly (Pl. 1, Fig. 7), an ant (Pl. 1, Fig. 8), and wasp 
(Pl. 1, Fig. 9). Nor is this the only group of Coleoptera 
which affords us examples of this fact. Thus in the 
genus Scolytus (Pl. 1, Fig. 4), the larve (Pl. 2, Fig. 4), 
