MUSCULAR SYSTEM. 265 



much in form as those organs themselves. We have already taken a 

 general notice of them in our description of those organs. Different 

 layers are detected in them, the exterior of which retains and turns 

 back the prepuce; the inner ones, which lie between the valves them- 

 selves or pass on to them, open and shut them. Straus, in his anatomy 

 of the cockchafer, has given a very elaborate description of all these 

 muscles as they are found in that insect, and which is the less desirable 

 to be repeated here, as from the (indeed but limited) investigations 

 made by myself in other insects, they are subjected to very considerable 

 differences. The more comprehensive representations of all the modi- 

 fications of the external as well as internal sexual organs, which I 

 purpose one day undertaking, will then serve to fill this gap, and until 

 then these indications may suffice. 



181. 



THE MUSCULAR SYSTEM OF LARVJE. 



The muscular system of the larvae of those orders of insects having 

 an imperfect metamorphosis agrees with that of the perfected creature, 

 with the exception of the mere indication of the presence of the 

 muscles of the wings ; we have therefore nothing further to say of 

 them than that these muscles of the win^rs, during; the several moult- 



O ' O 



ings, and particularly during the pupa state, acquire the size they are 

 intended to retain during the imago state of the insect. 



But the muscular system of the other orders, particularly of the 

 Lepidoptera and Hymcnoplera, is very different; the larvae of the 

 Coleuptera display much more conformity with that of the developed 

 beetle, for they are of all the most perfect larvte, and in the structure 

 of their feet agree very much with their perfected state. 



The most conformable muscular distribution in all larvee is found in 

 the abdomen, in which two straight, broad, band-shaped muscles 

 descend both the ventral and dorsal sides and connect every two seg- 

 ments together, the muscle itself being intimately united with the 

 connecting membrane of the several segments. 



Beneath these two large muscles, which may be called the longi- 

 tudinal muscles of the back and belly, lie smaller ones, which pass 

 obliquely from the connecting membrane at the anterior margin of a 

 joint to the corresponding part of the posterior margin of the same 

 joint, which may be therefore called the oblique dorsal and ventral 

 muscles. They strengthen the connexion of the joints together, and 



