the British Neuroptera-Tlanipennia. 151 



Family I. SIALID.E. 



The characters of the family, so far as native insects 

 are concerned, are those of the genus. 



Genus I. Sialis, Latreille. 



Head transverse ; antennce simple, short ; ocelli absent ; 

 lahrum sub-trigonate and deeply notched in the middle 

 in the (Jj (PI- VIII. fig. 1 g) , rounded in front and with 

 a very slight notch in the 9 * (PL VIII. fig. Ih) ; maxil- 

 lary lohe small, simple ; lahium small. 



Prothorax large, quadrate. 



Abdomen short and robust; in the male provided at 

 the apex above with a fleshy lobe, whence are protruded 

 two downwards-directed sub-transparent appendices; 

 beneath is a valve capable of being moved downwards in 

 a vertical direction. 



Fourth joint of tarsi cordate (PL VIII. fig. li) . 



Wings more or less smoky, the veins very strong; 

 anal portion of the posterior pair moderately developed ; 

 sub-costa and radius becoming confluent before the apex ; 

 costal area with numerous transverse nervules, which are 

 straight or slightly curved, excepting in the ill-defined 

 pterostigmatical region, where they are strongly oblique ; 

 sub-costal area with one transverse veinlet, placed near 

 the middle; transverse discal nervules few, placed in 

 three iU-defined rows. 



Larva aquatic ; very elongate, furnished at the sides 

 with seven pairs of articulated filaments, by means of 

 which it swims, and which also serve for the purpose of 

 respiration ; the abdomen ends in a long setose tail (see 

 Westw. Introd. ii. 50, fig. 64, 18) . When about to change, 

 it forms a cell in the bank ; the pupa is lively, and 

 changes to an imago within the cell. Eggs deposited 

 in large broad masses on the leaves of plants and other 

 objects in the neighbourhood of the water ; but often at 

 a distance therefrom that must cause the young larvae, 

 when hatched, to make a considerable terrestrial journey. 



We have two species which differ especially in the 

 form of the ventral valve in the male. 



* This diversity in the form of the labrum in the two sexes, does not 

 appear to haA'e been hitherto noticed. 



