cv 



these special characters appear to have escaped notice entirely, 

 it is desirable to record them now. 



Of the genus Pycnocentria there were two species, P. evecta 

 McL., and P. aureola McL., in the collection, and scent-fila- 

 ments are i^resent in each. In P. aureola the form of the fila- 

 ments is somewhat obscure, and in no examples were they 

 sufiiciently extended to enable me to take a satisfactory photo- 

 graph. Treatment with caustic potash rendered the filaments 

 invisible. I have been unable with the limited amount of 

 material at my disposal to obtain any very clear idea as to 

 their form and origin. In appearance they are small, somewhat 

 shapeless and white, and protrude from each side of the 

 maxillary palpi. 



In P. evecta the filaments which have a slight purple tinge 

 are more decided in their outline, and the containing walls 

 are hard enough to withstand the action of potash. They seem 

 to originate between and level with the centre of the oculi. 

 When not in use they are retracted and lie across the face 

 inclining towards each other, and are then covered not only by 

 the U2)turned maxillary palpi, but also by a special quadrangular 

 plate, which is hinged along the lower edge and is lined with 

 stout hairs. There is a short branch towards the base of each 

 filament, and still further towards the base is a group of stout 

 hairs. 



The filaments are elastic even after death. They can be 

 extended to a considerable length with the point of a needle, 

 contracting again when the needle is removed, and, although 

 they show a certain resemblance to the filaments in Hydroptila 

 sparsa Curt., they are clearly extensile and not eversile as in 

 this species. 



In addition to these two filaments another filament is found 

 at the base of each anterior wing, and in contrast to the head 

 filaments is covered all over with fine hairs. It is withdrawn 

 when not in use into a sheath, formed by a fold in the wing 

 membrane. Similar filaments occur in P. aureola. 



No trace of androcouia could be found on the head, though 

 there are scale-like hairs on portions of the anterior wings. 

 The filaments occur in the male sex only, and in the females 

 the hairs of the wings are normal. 



