OF THE LARVA OF PYG^RA BUCEPHALA. 183 



just above the upper end of 46, and passing downward is inserted just below the lower 

 end of 53. 



No. 52 is absent. 



No. 55 is single in the sixth segment. 



Nos. IG and 17 approach nearer to one another, and separate a little from 18. 



Nos. 47 and 48 are absent. 



No. 49 in the fifth and sixth segments is completely double, and stronger than in the 

 fourtli segment, which indicates that the prolegs of these segments act in a somewhat 

 different manner. 



The gastric muscle 9 rises, as in the larva of Cosstis, on the upper side of 21. 



Seventh Abdominal Segment. — 0\ving no doubt principally to the absence of prolegs, 

 this segment differs much from those that immediately precede it. Thus 47, 48 and 56 

 are entirely absent. 49 and 50 also, though present and weU-developed, are much shorter 

 than usual. 



On the other hand, in the sjiecimens I examined there were two new muscles Ijdng 

 under 10 and 11, and inserted below them in front. 10 and 11 approach one another in 

 front, and sometimes even unite together. 



No. 25 has completely imited with 24, and 26 lies on the lower side of these two muscles. 



To represent 31, 32, 57 and 58, there are fom* small variable muscles which seem to be 

 of little importance. 



No. 46 also is very thin and weak, so that it is probably of little functional utility, and 

 only present to fulfil the general law of arrangement of the muscles. 



No. 51 is single and small. It rises at the lower end of 49 and passes to the front of 

 34, as in the anterior abdominal segments. 



No. 62 is absent. 



No. 53 is parallel and similar to 54, though a little shorter ; these two muscles are very 

 unlike ia front, but become gradually more and more alike. 



No. 56. As there are no prolegs to tliis segment, the series of muscles marked 56 is 

 absent. 



Nos. 57 and 58 are represented by two small muscles parallel and similar to 31 and 32. 



Eighth Abdominal Segment. — In this segment the muscles have become much narrower 

 and weaker, and 31, 32, 33, 34, 50, 53 and 56 are absent. 



Nos. 12 and 13 have almost coalesced, so as to form one small muscle, and the same 

 has taken place with 14 and 15. 



No. 4 has entirely disappeared, while 3, on the other hand, is double ; as also happens 

 in the larva of Cossus. 



Nos. 7, 8, 10 and 11 have become parallel, and seem to form one series. 



In the Ninth Abdominal Segment the diminution of the muscles in size and number has 

 proceeded still fm-ther ; 3, however, is double, as in the preceding segment, and 4 makes 

 its appearance again. 



Indeed the number of missing mviscles is much greater than of those which are pre- 

 sent. These are, Nos. 1, 2, 3, 4, 5, 6, 7, 16, 17, 18, 21, 37, 38, 50 and 51. 



The first six of them resemble the same muscles in the prececUng segment. 



