101 



of the flashes. Small electric bulbs had been used to imitate both 

 the male and the female flash, and this had been so well achieved 

 that the " flashing" of the bulbs had been answered by the females 

 or the males, as the case might be. 



Mr. E. Step's exhibits included the following British Crustacea: — 

 A female Portunns piiher, with the mass of ova attached to the 

 appendages of the abdomen ; Callianassa suhteyranea ; Thia polita, 

 male and female; Galathea .svy^rt/^Z/'cz-fl, and examples of the same 

 species parasitized by I'leurocrijpta (jalaUcc, its presence shown by a 

 considerable bulging of the carapace on the left side ; Ebalia tuberom, 

 Hijaii cnarctatas ; and Xantho incisus. 



Mr. Step also exhibited the rare dipteron Of/codes {libbosus, on 

 which he read the following note : — 



" This little hump-backed spider-fly was taken in my garden at 

 Ashtead last summer ; and I am indebted to Mr. Andrews for its 

 identification, and for references to records of its previous capture. 

 It is a representative of the family Acrocerida, whose members are 

 characterized by a weakness for destroying spiders by feeding upon 

 them internally as larvte. Oi/codes iiibbosus is an exceedingly local 

 species, and apparently rare in its few localities. Curtis (quoted iDy 

 Verrall) records it from Wimbledon Common and the adjoining 

 Coombe Wood ; and a specimen in the Oxford Museum is labelled 

 " Richmond Park, July 4th, 18B5." Its principal locality today 

 appears to be the New Forest ; but it has been recorded also from 

 two localities in Herefordshire, and one in Suft'olk ; to which must 

 now be added Ashtead, Surrey. The head of the fly is remarkably 

 small, and consists almost entirely of the two compound eyes. The 

 great disproportion between the tiny head and the high rounded 

 body, gives one the impression that the latter would be normally 

 much smaller, but that it has been inflated by some diseased con- 

 dition. This eflect is intensified by the fact that the thorax is 

 covered by a rather matted coating of whitish-grey hairs, which 

 gives it the appearance of a house-fly that has been killed on our 

 windows in autumn by the activity of the fly fungus. It is just 

 possible that it may not be as rare as supposed, but that specimens 

 may be passed with a cursory glance in the belief that they are 

 merely diseased house-flies. 



"Having regard to the fact that the food of the larva is plentiful, 

 and that feeding under cover it runs few risks, one would expect the 

 fly to be quite common. But it has an enemy who takes effectual 

 steps to keep down its numbers. This enemy is a hyuaenopteron, 

 Crabro internijjtus, a little wasp that makes tunnels in decaying wood, 



