3 20 



THE RIVER-SIDE NATURALIST. 



The insects included in the family Perlidce have the 

 wings incumbent during repose ; the reticulations vary. 

 The head large ; ocelli three ; abdomen frequently with 

 two articulate setae ; tarsi always simple. They frequent 

 damp places. Those indigenous to this country are divided 

 into five genera 



I, Per/a ; 2, Isogenus; 3, Chloroperla; 4, Nemoura; 5> 

 Leuctra. 



In the genus Per/a (Geoffroy) the insects are usually of 

 large size, and the sexes are very dissimilar, the males 

 having the wings much abbreviated. Their legs are also 

 longer, and their general habits very dissimilar to the 

 females, which have large expansive wings and shorter 

 legs, the palpi in both sexes of different length, the maxil- 

 lary ones much longer. 



PERLA MARGINATA. 

 i, Perfect Insect; 2, Larva. 



Perla marginata is the Stone-Fly of the north of England 

 and Scotland, where it abounds in June and beginning of 

 July. Described as follows : 



" Fuscous ; antennae as long as the body ; head moderate, 

 black, varied with yellow, with some glossy elevated spots, 

 a longitudinal dorsal channel having an elevated line on 

 each side ; abdomen more or less ochreous or yellowish 

 on its sides and towards the apex ; setae as long as the 

 antennae ; legs yellowish ; wings fuscescent with darker ner- 

 vures ; pupa pale, fuscous, with dusky spots " (Stephens). 



