66 MODERN CLASSIFICATION OF INSECTS. 
(Mémoires, tom. iii. Mém. 5.) has described many of the varieties in 
the cases formed of leaves, twigs, straws, wood, stone, sand, or shells. 
He has also figured (Jbid., pl.12, 13.) the transformations of P. 
striata (according to Linnzus and Pictet), and, in pl. 14. f. 1—4., 
those of a species which Linnzus quotes as P. grandis, but which ap- 
pears to agree both in the spirally-arranged case, and the spotted wings 
of the imago, with the P. varia (Pictet, pl. 11. f.1.). The cases of a 
minute species are also represented, together with the imago, in the 
same plate, but too vaguely to be determined; they are probably a 
minute species of Mystacida ; whilst, in the fifteenth plate of the same 
volume, he has figured the cases of the larvae of a Mystacida Latr., 
the hind legs of which are greatly elongated. 
De Geer has entered more minutely than Reaumur into the 
details of the habits and structure of these insects, of which he traced 
five species through their different states, These are P. pellucida 
Oliv., Pictet (Mém., tom. ii. pl. 11, 12.), P. grandis (pl. 13. f. 1—17.), 
P. grisea (pl. 13. f. 18—21.), P. fusca? (according to Goéze’s edit., 
vol. ii. p. 442.), and P. bimaculata Zinn., which is evidently a 
Mystacida. He, moreover, figured a variety of cases of different 
forms, of which he had observed the larvae, and of which some 
(pl. 15. f. 15—17.) are of a singular form, being apparently composed 
of fine sand, of an elongate-ovate shape, with a broad mouth and two 
protuberances at the opposite extremity. They probably belong to a 
species of Hydroptila. He, moreover, figured several perfect insects 
of which he had not observed the larvee. 
Rosel (Abhandl. von Ins., vol. ii, Ins. Aquat., tab. 14—17.) has 
figured various cases, together with the transformations of three 
species, which have been cited as P. grandis, striata, and rhombica. 
With the exception of Reaumur’s figures in his fifteenth plate, above 
referred to, and those of De Geer’s of P. bimaculata (all of which are 
destitute of sufficient precision in the details), the various larve 
figured by these authors are all referable to one type of form, 
having the head and three thoracic segments scaly, the legs mode- 
rately long, the basal segment of the abdomen furnished with 
three fleshy protuberances, and the third armed with two short 
hooks, with the external crgans of respiration, consisting of slender 
soft filaments, arising separately, and lying transversely on the 
upper and under sides of the abdomen. Such are the characters of 
the larve of the genus Phryganea, as restricted by Pictet. Those of 
