75 INSECTA, 
the form of which, as well as that of the tube itself, varies accord- 
ing to the species. 
In fixing their portable dwelling, they so manage it that the aper- 
ture, which is at the point d’appui, is never obstructed. 
The nymph is furnished anteriorly with two hooks, which cross 
each other and somewhat resemble a rostrum or snout. With it, 
when the period of its last metamorphosis has arrived, it perforates 
one of the grated septa in order to procure egress. 
Hitherto immovable, it now walks or swims with agility, by means 
of its four anterior feet, which are free, and furnished with thick 
fringes of hairs. The nymphs of the large species leave the water 
altogether, and climb on various bodies, where their final change is 
effected. -The small ones simply rise to the surface, where they are 
transformed to winged Insects, in the manner of the Culices and va- 
rious Tipulariz; their exuvium serves them for a boat. 
In some the inferior wings are evidently wider than the others, 
and plaited. 
SERIcOSTOMA, Lat. 
Where, in one of the sexes, the maxillary palpi are in the form of 
valvulz, covering the mouth in the manner of a rounded snout, and 
triarticulated; under them is athick and cotton-like down. Those of 
the other sex are filiform, and consist of five joints(1). 
PHRYGANEA proper. 
Where the mouth is similar in both sexes, and the maxillary palpi 
are shorter than the head and thorax, and but scarcely pilose. 
P. grandis; Rees.; Insect., II, Ins. Aq. cl, 2, xvii. The largest 
species in France; antennz as long as the body; superior wings 
greyish-brown, with cinereous spots, a longitudinal black stripe, 
and two or three white dots at their extremity. 
The tube of its larva is invested with little pieces of bark, or 
ligneous matters arranged horizontally. ; 
P, striata, L.; Geoff., Insect., II, xiii, 5. About an inch long; 
fulvouss; eyes black; nervures somewhat darker than the rest of 
the wing. 
P. rhombica; Res., Insect., II, Ins. Aq., cl, 2, xvi. Length 
(1) A genus established on a species from the environs of Aix, sent to me by 
M. Boyer de Fons-Colombe, and which has been also brought from the Levant 
by M. de Labillardiére. 
