48o 



NEUROPTERA 



C the position of the wing on the exterior of the body is due 

 to the stripping off of the chitinous integument, or to a process 

 of eversion. or to both. 



Fig. 324. Development of wings 

 of Phryganeidae. (After Dewitz.) 

 A, Portion of body-wall of 

 young larva of Trichostegia ; 

 ch, chitin, forming at r a pro- 

 jection into the hypodermis m ; 

 r and d forming thus the first 

 rudiment of the wing. B, The 

 parts in a largely grown larva ; 

 , c, d, b, the much grown hypo- 

 dermis separated into two parts 

 by r, the penetrating extension 

 of the chitin ; v, mesoderm. C, 

 "Wing-pad of another Phryganeid 

 freed from its case at its change to 

 the pupa ; b, d, outer layer of the 

 hypodermis, m, of the body-wall ; 

 V, inner layer without nuclei. 



There are about 500 species of this family of Insects known as 

 inhabiting the European region, and about 1 5 of this number occur 

 in Britain. These are arranged by M'Lachlan ^ whose zealous 

 and persevering work at this neglected family of Insects is beyond 

 praise in eight sub-families, on a system in which the structure 

 of the maxillary palpi plays a principal part ; they are called 

 Phryganeides, Limnophilides, 

 Sericostomatides, Leptocerides, 

 Oestropsides, Hydropsychides, 

 Ehyacophilides, Hydroptilides. 

 The first three of these form 

 the division " Inaequipalpia,** 

 in which the number of joints 

 in the maxillary palpi differs 

 in the two sexes, but is always 

 five in the female. 



Phryganeides. This group 

 includes the largest forms of 

 the family, and appears to be 

 almost confined to the tem- 

 perate regions of the northern hemisphere 



\^ 



Fig. 325. Cases of British Trichoptera. A, 

 Of Odmitocerum albicorne ; A}, its ter- 

 mination ; B, quadrangular case of Crtm- 

 oecia irrorata ; B^, mouth of case. 



This feature in 



^ Monograph of the British Trichoptera in Tr. ent. Soc. London, tliird series, vol. 

 V. 1865 ; and Monographic Revision of the European Trichoptera, 1874-1880. 



