388 BRITISH LEPIDOPTERA. 



first three segments deep black, divided down the middle by a fine 

 yellow line on each of these three segments, whilst on each side of the line 

 is a round orange-yellow spot. Barrett describes the larva as " pale 

 grey, whitish beneath, with black head, the three following segments 

 having each a rather narrow, dark grey, horny plate, which almost 

 embraces the segment ; each has a blackish dividing line down the 

 middle of the back and whitish spots on the sides ; the legs are large 

 and well-developed, with black claws." This description evidently 

 does not belong to the larva of A. opacella, and Hamm notes that "the 

 larva taken by Barnes at Wellington College did not agree with 

 Barrett's description, for this larva had lateral orange spots on the 

 prothorax." These orange-red spots are quite a character of the larva 

 of A. opacella. They are sometimes found also on the metatborax. 



Comparison of laev^e of Acanthopsyche opacella and Pachy- 

 thelia villosella. :;: — The heads of the larva? of both species are 

 similar in shape, but whilst that of P. villosella is rough, almost 

 granular, and dull in appearance, that of A. opacella is smooth and 

 polished, showing only a very faint reticulation. In colour, the head 

 of P. villosella is yellowish-white mottled with blackish (the pale and 

 dark colour in about equal proportions), that of A. opacella is black 

 with a narrow white line from apex of clypeus to crown. The thorax 

 appears similar in each except that the central suture of the dorsal 

 plate on the metathorax is hardly apparent in P. villosella, whilst it is 

 distinct in A. opacella (this may be in part due to the darker colour of 

 A. opacella). A difference is observable in the appearance of the thoracic 

 plates similar to that exhibited by the heads, and the coloration 

 is equally different, for whilst P. villosella has a pale yellowish-white 

 mediodorsal band, very broad whitish subdorsal bands, and narrower 

 lateral bands (the mediodorsal across the pro- and mesothorax only, 

 the subdorsal and lateral" across all three thoracic segments), the bands 

 so broad as to leave only broad black bands of the ground colour, A. 

 opacella has a polished black thorax, with a narrow white mediodorsal 

 line across the pro- and mesothorax, and an orange spot on each side of 

 the posterior subdorsal area of the prothorax. The 2>i'olegs are similar in 

 shape and appearance, but the central depression of the foot is larger, 

 darker, and consequently more marked in A. opacella. The number of 

 hooks appears to be about four fewer in the latter than in P. villosella. 

 The plates at base of setse are more conspicuous in P. villosella than in 

 A. opacella. The abdomina are very different in colour, that of A. 

 opacella is smoky-black on the dorsum, whilst that of P. villosella is 

 almost uniform pale whitish-brown (Bacot). 



Pupation. — When the larva is fullfed it finds a suitable locality for 

 fixing its case and the hitherto open end of the case is spun to the 

 selected object and the larva turns round in its case. The hitherto 

 closed end of the case is then lengthened in the shape of a funnel, the 

 latter being soft and elastic, although the end is not quite open till 

 after the female has burst from the pupa (Weaver). The larva (espe- 

 cially the female) spins a fluffy silken cocoon inside the larval case 

 before pupation. This effectually fills up the entrance, and possibly 

 acts as an effective bar against the entrance of many enemies (Cowl). 



* The larva of A. opacella in hybernating skin (probably almost full-fed), 

 freshly killed, in spirit ; that of P. villosella possibly in last skin, killed and kept in 

 spirit since the spring of 1898. 



