In Galleria mellonella L. denervation of intersegmental muscles in the 4th, 5th 

 and 6th abdominal segments in the final instar larva or prepupa causes them to 

 degenerate during metamorphosis although they normally persist throughout 

 the pupal stage. In the Saturnids Hyalophoracecropia'L. smdAntheraeapernyi 

 Guer. similar operations had no effect in a comparable period of time. Variations 



between insects of different groups is to 

 be expected but such a difference be- 

 tween such closely related insects \vas sur- 

 prising. I suggested that the difference in 

 response might be related to the occurren- 

 ce of pupal diapause in the saturniids and 

 not in the wax-moth. This hypothesis has 

 since been tested. 



Experiments on involution 

 of muscles 



Fig. 1. Diagrams to show ventral, la- 

 teral and dorsal longitudinal muscle 

 bands of the abdomen of a saturniid 

 larva (left) and the parts of these bands 

 that persist in the pupa (right). The 

 pattern shown in segment III of the 

 pupa may occiu* in Antheraea poly- 

 phemus. 



The multivoltine Actias sehne Hbn. and 

 the egg-diapausing Antheraea yamamai 

 Guer. were used and it was found that 

 ganglionectomy frequently resulted in 

 muscle degeneration in abdominal sege- 

 ments 4,5 and 6. These results supported 

 the hypothesis but similar experiments 

 made with Antheraea pernyi reared in long- 

 day photoperiod and hence non- diapaus- 

 ing gave identical results to those obtained лvith diapausing broods. 



In the work described so far the condition of the pupal intersegmental 

 muscles in the 3rd abdominal segment was purposely disregarded because 

 studies on Antheraea polyphemus had shown that the pattern of persisting 

 muscles in that segment varied. It was found, however, that the pattern 

 of intersegmental muscles in the 3rd segment of the pupa of Antheraea pernyi, 

 Actias selene and Samia cynthia Mel. was constant (Fig. 2.). 



The 3rd abdominal ganglion Avas removed from fully grown larvae of 

 A. pernyi, A. selene and S. cynthia. The resulting pupae frequently lacked 

 part or all of the muscles of the 3rd segment (Fig. 3). In kS. cynthia and A. selene 

 only the muscles in the 3rd segment were affected but in A. pernyi section (a) 

 of the dorsal band of the 4th segment always degenerated. 



In 8. cynthia the removal of the 4th ganglion as well as the 3rd had no 

 effect on the muscles of the 4th segment. In this respect 8. cynthia differs 

 from A. selene in which removal of both ganglia results in degeneration in the 

 4th segment (Fig.3). 



100 



