OF THE LARVA OF PYGÆRA 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 z 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 v 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 first 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 following variations :—First, 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 first 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. 
i No. 27 was absent in the third abdominal segment; in the first two it rises on the 
dorsal side of 28 and passes forward parallel to that muscle. i 
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 abdominal segment it is 
difficult to distinguish them from 31 and 32. 
In the first abdominal segment, the four small muscles marked 29, 30, 57 and 58 appear 
to correspond with those so named in other segments; but it is difficult to determine 
Which is which. : : å 
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, 
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. i 
Third Thoracic Segment.—The muscles in this segment differ so much from seit 
that have been previously described, that in many cases I feel very doubtful whether 
have used the right numbers to represent them. A careful examination of the thorax in 
and in front 
