42 TRANSACTIONS, NATURAL HISTORY SOCIETY OF GLASGOW, 



V. 



ON THE OCCURRENCE OF MICRODON 

 MUTABILIS, LIN., IN THE WEST OF 

 SCOTLAND. 



BY P. CAMERON, V.-P. 



[Read 27th November, 1883.] 



At Ballantrae, Ayrshire, I found last year in a 

 nest of the Common Ant, Lasius niger, situated 

 in the stump of an old tree, a curious object, 

 which, when I first saw it, and before examina- 

 tion, I took for a slug. It was elliptical, brownish- 

 grey in colour, flat on lower side, the sides of the 

 ventral surface ciliated, the back reticulated, convex, 

 and bearing anteriorly two projecting horns (which 

 are the processes by which they breathe). A note 

 by Laboulbene {Ann. Soc. Ent. Fr. Bull. 1882, p. 118 

 and p. 128) gave me some indication as to what 

 the creature was, and the finding of more specimens 

 during the spring of this year near Glasgow, enabled 

 me, by the aid of a paper by G. A. Poujade (Ann. 

 Soc. Ent. Fr. 1883, p. 23, PL 1), to recognise them as 

 the larvae and pupae of the fly Mlcrodon mutahilis, 

 Lin. All that seems to be known about the larva 

 is that it is always found in the nest of the above- 

 mentioned ant, that it is generally found in the 

 lower galleries, and that before turning into a pupa 

 it goes near the surface. The larvae, I observed 

 myself, were resting motionless, and adhered closely 

 to the sides of the gallery, from which they were 

 only with difficulty removed. No one has ever 

 noticed them feeding in the nests ; the ants pay 

 little or no attention to them, so it would appear 

 that they are not injurious to their hosts ; and few 

 of the larvae are found in one nest. The group of 



