152 
Prof. Miall and Mr. N. Walker on the 
The larva of Psychoda humeralis, Meig., found by 
Gimmerthal (No. 7) in rotten potatoes, answers the 
description of the terrestrial-tailed larvse, as given above. 
The species to which it belongs is a Psychoda in the 
narrower sense. (It was a lapsus calami on the part of 
Haliday, as I have already shown above^ sub Nos. 11 
and 12, when he placed it among the Pericomse.) 
When Gimmerthal says, *^the spiracles are plainly 
visible along the sides, as in a caterpillar/' he must have 
been misled by Bouche. I have had occasion to observe 
a larva of the same group in North America, and found 
it to be amphipneustic. In a MS. note among my 
papers I find stated, " the anterior spiracles of the first 
thoracic segment are very apparent in the shape of short 
tubes. Large tracheal trunks can be seen distinctly 
running into the tail. The body is dirty whitish, 
with extremely short, erect bristles; there were no 
lateral bristles like those figured by Bouche. The seg- 
ments are marked by distinct incisures and transverse 
wrinkles. 
The larvae I have been hitherto discussing belong to 
the group of the terrestrial-tailed larv£e of Psychoda in 
the narrower sense of Haliday. It remains for me now 
to reproduce the passages of Walker's Ins. Brit, con- 
cerning the larvae of Pericoma, Haliday, and Ulomyia, 
Haliday. They are : — 
(P. 256.) Pericoma. "Larva with rows of hairs; 
inhabits water; bent into a ring; the tufts of curved 
hair detaining a covering of mud.'' 
(P. 260.) P. nuhila, Meig. Reared from larvae found 
on fallen leaves, immersed in the water of pools or slow 
streams." 
(P. 261.) Ulomyia, The larva lives in clear, running 
water, and has, like a dorsibranchial Annelid or Phyllo- 
doccy down the back two rows of acute, lanceolate, 
foliaceous, branchia-like appendages; each row consists 
of three pairs on each segment, viz., a pair on each of 
the three folds or subdivisions of the segment. Other- 
wise most like the larva of Pericoma, Ulomyia hirta 
was reared from larv^ found on fallen leaves lying in a 
waterfall of a clear rivulet." 
Dr. F. Miiller (No. 14) in 1888 described and figured 
two Brazilian aquatic larvae, belonging perhaps to as yet 
undescribed genera of the same family. 
