( 141 ) 
IV. The Life-history of Pericoma canescens (Psyclio- 
didge). By Professor Louis C. Miall, F.K.S., 
and Norman Walkee. With a Bihliograjphical and 
Critical Appendix, by Baron Osten Sacken^ Hon. 
r.E.s. 
[Read Feb. 6th, 1895.] 
. Plates III. and lY. 
Little appears to be known of the life-bistory of any 
members of this family. Short and dry accounts of the 
larva and pupa of Psychoda phalsenoides {nervosa), 
which is found on decaying vegetation, are given by 
Bouche,* Perris^t and Curtis. J Fritz Miiller has 
described the peculiar respiratory organs of several 
larvae of this family, which occur on wet rock-surfaces 
at Blumenau (Brazil). He notices in particular that 
open spiracles and tracheal gills co-exist in them. At 
the end of the abdomen are two large spiracles sur- 
rounded by a circle of hairs, and leading to the tracheal 
trunks. Each trunk sends off branches to two or three 
pairs of ventrally placed anal papillge, which are finger- 
shaped and retractile, being retracted in air and pro- 
truded in water. In one species the larva, on entering 
the water, sometimes takes down with it an air-bubble, 
which clings to the hairs around the spiracle. § 
The larvae and pupas of one species of this family have 
turned up in considerable numbers in a paved channel 
receiving over-flow^ water from the stream at Meanwood, 
near Leeds. It is found also on the banks of a muddy 
pond at Adel, near Leeds. The larva feeds upon green 
algae, and is found entangled in the filaments. It is 
wetted with water, and must often be immersed for a 
long time together. It is not, however, altogether 
Naturg. d. Insekten, pp. 28, 29, pi. ii., figs. 20-22 (1834). 
+ Ann. iSci. Nat. Zool., 2e ser., torn, iii, po. 346-348, pi. 6b 
(1840). 
:|: Journ. Roy. Agr. Soc, vol. x., p. 403, pi. v., figs. 47-50 
(1850). 
§ Entom. Nachrichten, Sept., 1888. 
TRANS. ENT. SOC. LOND. 1895. — PAET I. (aPRIL.) 
