OF THE LARVA OF PYGiERA BUCEPHALA. 177 



mentioned in connexion with those muscles. The fascicles of which this series is com- 

 posed vary considerably in number and form in different specimens. 



No. 57 (perhaps part of x of Lyonet) rises near the middle of the upper side of 56, and 

 passes straight back to the posterior end of the segment. 



No. 58 (perhaps part of x of Lyonet) rises close to 57, and passes backward and down- 

 ward to the posterior end of the segment. 



Besides these muscles, there are two small ones (86 and 87) which lie under and parallel 

 to 53, and another (88) which runs under and transverse to 46, 47, 48 and 53. 



Anterior Segments. — The fii'st two abdominal segments are very similar to one another, 

 and may therefore conveniently be considered together. The chief differences which exist 

 between them and the third abdominal segment depend on the absence of prolegs. 



It has been already mentioned that the muscle 2, belonging to the second abdominal 

 segment, is quite free from the skin, being attached by its ends to the corresponding 

 muscle of the preceding and succeeding segments. The other superior longitudinal muscles 

 very closely resemble those of the third abdominal segment. In the first abdominal 

 segment there are the two follo^\ing variations : — Fu'st, Nos. 10 and 11 are either united 

 together in front, or at least closely approach one another, — a tendency which is more 

 developed in the two posterior thoracic segments, where they have completely coalesced ; 

 and secondly. No. 6 sends off a branch from the upper side of its anterior end. 



Nos. 10 and 11 reach to the fore end of the fij-st abdominal segment, and converge in 

 front or sometimes unite. 



In the ventral longitudinal series. No. 18 of the first abdominal segment is considerably 

 swollen anteriorly, so as to overlap 21, which in this segment is inserted as nearly as 

 possible on the same transverse line as 16, 17 and 18, and under the latter. 



No. 22 of the same segment is single in front. 



No. 27 was absent in the thu-d abdominal segment ; in the first two it rises on the 

 dorsal side of 28 and passes forward pai'allel to that muscle. 



Nos. 29 and 30 are small in the second abdominal segment, having the same attach- 

 ment posteriorly, but not passing so far forward. In the first abdomin&l segment it is 

 diflicult to distinguish them from 31 and 32. 



In the fiii'st abdominal segment, the four small muscles marked 29, 30, 57 and 58 ap])ear 

 to correspond with those so named in other segments ; but it is diflicult to determine 

 which is which. 



No. 85 is completely simple in the first abdominal segment, where also 36 is wanting. 

 In this segment also there are only three muscles to represent 40, 41, 42, 43 and 44, 

 though it is difficult to say which of the five have disappeared. 



In both these segments 46 is inserted under or rather outside of 49 above, and in fi-ont 

 of it below ; the dorsal end of 49 is inserted just above 46, and above 51 below ; and 48 

 is in general quite single. 



Nos. 47, 48, 50, 52, 53 and 56 are completely absent in both segments. 



Third Thoracic Segment. — ^The muscles in this segment differ so much from those 

 that have been pi'eviously described, that in many cases I feel very doubtful whether I 

 have used the right numbers to represent them. A careful examination of the thorax in 



