( 483 ) 
XIX. RemarJcs on the homologies and differencRS between 
the first stages of Pericoma, Hal., and those of the 
new Brazilian species. By Baron C. R. Osten 
Sacken, Ph.D., Hon. F.E.S. 
[Read Oct. 2nd, 1895.] 
The introductory paragraph, of Dr. Miiller's paper 
sufficiently explains its scope, whicli is to call attention 
to a group of very remarkable aquatic larvae of Psy- 
chodidse, discovered by Mm in 1881 in the environs of 
his residence in Southern Brazil, but of which he was 
unable, at that time, to make a more thorough inves- 
tigation. He has already made a short allusion to these 
larvse in the Zool. Anzeiger,^'' 1881, p. 499 (compare 
also Bertkau^s Entomol. Bericht, 1881, p. 145), and has 
called attention to their remarkable structural analogies 
with the larvae of Blepharocerid^e, which occur in the 
same running waters. Since then, in the '^Entomo- 
logische Nachrichten,"' Berlin, 1888, p. 273, Dr. F. 
Miiller has published a short article, accompanied by 
three figures, on the mode of breathing of two species of 
the same larvae. 
What Dr. Miiller offers us at present is a set of 
drawings of the early stages of the said Psychodidas, 
prepared in 1881, but never published. They are 
accompanied by an explanatory notice. The study of 
these insects is of extraordinary interest as a most 
remarkable instance of the power of adaptation among 
aquatic larv^; but in order fully to bring out this 
interest, they should be compared with some ordinary 
type of Psychodid larva. I'he present volume of the 
Transactions affords us the best occasion for such a 
comparison, as it contains the only scientifically satis- 
factory description of such a larva in Prof. L. C. Miall's 
and Norman Walker's paper : The Life-history of 
Pericoma canescens." I shall therefore attempt such a 
comparison. 
The principal of Dr. Miiller's figures (Tab. x., fig. 1) 
represents, much magnified, a dorsal view of the larva of 
TRANS. ENT. see. LOND. 1895. PAfiT 17. (dEC.) 
