1921.] 25 



wings varies a good deal, though they never overlap. In Mffn'ocnemiis 

 and the Ortliocladius group tlio wings are held in a roof-like position, 

 the steepness of the angle varying i)artly with the hreadtli of the wing, 

 those species with the hroadest wings showing the steepest roof ; the 

 wings of the females heing usually hroader than those of the males, 

 the roof-like jwsition is more notieeahle in this sex. Tn this group the 

 wings are usually in contact hy their upper (posterior) edges. In 

 Cricotojjus and the related Trichocladius, however, the wings are 

 slightly divaricated and the angle of the roof is comparatively slight ; 

 in these species we thus see an approach to the next group. 



The C\\\vonommi {Chironomus, Tanytarsus, and some small allied 

 genera) hold their wings flat or almost flat ; in Chironomus thev are 

 usually practically touching hy their inner (posterior) edges, while in 

 Tanytarsus they are more divaricate, lying quite free at an angle of 

 about 30° on each side of the body. In the genus Cliironomits, how- 

 ever, I have come across two species which are exceptions to the general 

 rule in holding their wings in a roof-like position. These sjiecies are 

 C. Jlarimanus Mg., as determined by Verrall (a species somewhat 

 resembling the common Pavatendijjes alhimaniis Mg.) and C. incertus 

 Wlk., a small green species. 



Tanypinae. — These insects do not raise their front legs. In the 

 Diamesa -group, as in Trichotanypus and the dark species of Tanypus, 

 (subgenus Afacropelopia, e. g. M. nehulosus Mg.) the wings are held 

 in a roof -like position, while in the lighter-coloured Tanypus (s. str.) 

 they are held flat and diverging at an angle of 4o° on each side of the 

 body. 



Ceratopogoninae. — There is great uniformity throughout this sub- 

 family, almost all the species settling in the normal manner with the 

 wings overlapping flat over the back, and all the legs in contact with 

 the surface. I have, however, recently found one notable exception. 

 Stilohezzia flavirostris Winn, (though not the other British species of 

 this genus) keeps its wings divaricate at an angle of 45"^ on each side. 

 Mallock mentions two American species {S. picta and S. antennalis) 

 which have this habit; the latter of these seems to be the American 

 representative of S.Jfavirostris. 



Orplinepliila when alive looks like one of the Ceratopogoninae. 



SiMULIIDAE. 



The front legs are often raised and waved about. The wings 

 overlap. j) 



