36 Dr. D. Keilin on the Larvce &c. of 



to Meigen(1818, t. i.p. 230), who found a young undeveloped 

 male of this fly in Polyporus versicolor. 



Zctterstedt (1851, t. x. p. 4071) quotes Behrens, Avho 

 hred this insect from a fungus Avhich he found on Jvylans 

 reyia. 



According to Winnertz (1863, p. 669), the larvse of 

 D. fasciata live in difl^'erent Polyporus and especially in 

 P. versicolor and ferrugineus ; he quotes also Kaltenbach 

 who bred J), macroptera, Winnertz, from Polyporus ignarius. 

 Schiller (1864, i. p. 428) reared D. fasciata from various 

 Polypori. 



Frauenfeld (1866, p. 200) found the larvse of this species 

 in Polyporus squamosus ; he also gave the first description ol: 

 the larval and pupal stages of this fly. Unfortunately, his 

 very short description does not contain any figure, and may 

 be applied to many other dipterous larv«. The only 

 characters of his description worth mentioning are the 

 following: (1) the intersegmental spaces are deeply con- 

 stricted, (2) the first segment of the thorax is large, and 

 (3) the posterior end of the body bears two protuberances 

 ended by a sharp spine. 



^Ye have, finally, to mention that the collection in the 

 Entomological Museum of Cambridge contains the pu] £e 

 and adults of Uitomyia fasciata, Mg., reared by Fryer (1910) 

 from Polystictus versicolor collected at Chatteris (Cambs) 

 and by H. Scott (1910) from the same fungus collected from 

 beech-stumps at Henley-on-Tliames. 



I received the larvae and pnpse of Ditomyia fasciata, which 

 will be described here, from Mr. F. W. Edwards, who found 

 them in a fungus, which he believes to be Polystictus veisi- 

 color, growing on old beech-stumps near Cainbridge and at 

 Baldock, Herts. 



Later on, I collected myself a few of these larvae in a 

 piece of wood covered and penetrated by the mycelium of a 

 fungus. 



According to Edwards, in nature the larvae usually live 

 upon the old fungi, but in his breeding-jars he observed 

 them attacking the fresh fungi also. 



The larvae are opaque white in colour and have very little 

 power of movement. Pupation takes place within the 

 fungus without the formation of any cocoon ; before the 

 emergence of the adult the pupa bores its way to the surface 

 and comes halfway out. 



The larva is 9*3 mm. long, with very deep intersegmental 

 grooves (PI. IV. fig. 14). 



