[ 173 ] 



XIII. On the Arrangement of the Ctitaneotis Muscles of the Larva o/Tygaera bucepliala. 

 By John Lubbock, Esq., F.B.S., F.L.S., F.G.S. ^c. 



Read February 18th, 1858. 



L/YONBT'S celebrated memoir on the larva of Cossns ligniperda, and Straus-Durckheim's 

 still more beautiful work on llelolontha vulgaris, are the most perfect, and indeed the 

 only monographs we have at all complete, on the general anatomy of any insects. 



The very complicated arrangement of the cutaneous muscles in the caterpillar of Cossns 

 inspired me with the wish to see how far the muscles of other larvae would agree with, or 

 differ from, this type. 



With this view I dissected with great care some larvae of Tipula oleracea and of 

 Ctenophora bimaculata ; but on comparing two or three specimens together, I found to my 

 astonishment very considerable variations. It then occurred to me to compare several 

 specimens together, in order to ascertain the nature and amount of these variations. The 

 lai'vse, however, of the different species of Tiptilidce so much resemble one another, that I 

 could not feel certain that these supposed variations were not rather specific differences. 



In order to remove this element of doubt, I selected the larvae of Fygcera bucephala, 

 which were obtainable in any numbers, and could not be confused with those of any 

 other species. Moreover, as some of these caterpillars live on oak- and some on beech- 

 leaves, I was curious to observe whether this difference in the food induced any alterations 

 in the muscles. It did not, however, appear to have any such effect. 



The full-grown caterpillars are about two inches long, and of a brown colour with dark 

 longitudinal bars. 



I have divided my paper into three sections : — 



First, a description of the cutaneous muscles of the larva of FygcBra. 



Secondly, a description of the variations observed in these muscles ; and 



Thu'dly, a comparison, as complete as possible, of these muscles in Fygcera with the 

 corresponding muscles of other larvae. 



In examining closely Lyonet's drawings, I have always found them inconveniently 

 small : moreover he has represented alternately the two sides of the insect, so as to reverse 

 the directions of many of the muscles ; and as he has also figured the same muscle in dif- 

 ferent plates, it is difficult to ascertain the exact number of muscles in each segment. 



In my drawings I have always represented the left side of the insect, and have never 

 introduced the same muscle into two plates. 



I propose to cormnence my description of the muscles at the third abdominal segment, 

 and then, passing forward on the one hand and backward on the other, to point out the 

 differences which exist in the muscles of the anterior and posterior segments. 



2 a2 



