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OF THE LARVA OF PYG^ERA BUCEPHALA. 181 



Nos. 69 and GO have united together. 



No. 61 ovei'laps (50 at the fore end. 



No. 03 is generally, if not always, double. 



Firsi Thoracic Segment. — In the posterior part of this segment several muscles are 

 wanting, and in the anterior they differ widely from the usual type, being principally 

 modified so as to effect rotations of the head. 



The most striking alteration is the presence of the muscle marked 82 (C+of Lyonet), 

 which is attached in front to the posterior border of the head, and passing through the 

 present segment is attached by four heads along the middle dorsal line of the second 

 thoracic segment ; nor did it vary in any of the specimens examined by me. There does 

 not seem to be any muscle comparable to it in the other segments. There are yet three 

 other muscles which seem to be peculiar to this segment. No. 80 rises close to the fore 

 end of 82, and passing over 19, 20 and 26, is attached by two heads near the middle 

 ventral Une, close to 56. No. 81 rises with the preceding and follows nearly the same 

 com-sc, but passes imder 19, 20 and 26. No. 83 rises from the fore side of the spiracle 

 and passes forward to the upper end of 46. 



No. 1 is in this segment divided into two or three separate muscles, which are attached 

 side by side behind, and fixed to the fore part of the segment, or rather into the mem- 

 brane connecting the head with the thorax. 



No. 4 is attached in front, close to 1. 



No. 6 is double ; in some cases however it is united in front. The one fascicle rises 

 under or at the side of 1, the other rather further down, and both are inserted on the 

 ventral side of 4. 



No. 7 lies at the lower side of 6 and parallel to it. r 



No. 8 perhaps is Avrongly identified, since it here lies under 10 and 11, rising close to 

 the fore end of the latter and passing back to the hind end of the former. No. 9 is 

 much broader than iisual. 



Nos. 10 and 11 arc both present, and offer no peculiarity, except that 11 is expanded 

 and sometimes double in front. 



Nos. 12, 13 and 14 are absent. 



No. 15 is a straight muscle, longer than, and lying at the side of, 9. 



No. 16 is completely double ; in fi-ont it hes at the upper side of 17, and under it behind. 



No. 18 rises under the hinder end of 21, and passes forward with a slight incKnation 

 dowTiward to be inserted at the lower side of the fore end of the same muscle. 



Nos. 19, 20 and 26 are parallel to one another; they rise under 17 and 21, and 

 pass forward and upward to be inserted at the anterior end of the segment, not far 

 above 16. 



No. 22 rises under the fore end of 16 and passes backward and upward to the hind 

 end of 6. 



Nos. 23, 28, 29 and 34 seem to be absent. 



No. 31 is pei'haps wrongly identified. It rises under 16 and passes upward and forward 

 in front of the spiracle. 



Nos. 37 and 38 appear to be absent. 



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