298 



Nematocera, and for this reason I have placed them in this super- 

 family. 



SUPERFAMILY CHARACTERS 



Larva. — Head complete; mandibles opposed; antennae well de- 

 veloped. Abdomen with lateral abdominal spiracles, functionless in 

 Simuliidae and possibly so in Scatopsidae ; prothoracic and anal 

 spiracles large in Bibionidae and Scatopsidae, the anal pair separated 

 and more or less elevated; abdomen in Simuliidae with apical pro- 

 trusive blood-gills. 



The larvae of Simuliidae superficially resemble those of some 

 Chironomidae, but may be separated by the long mouth-brushes, 

 which consist of many slender branches upon a common base, open- 

 ing and closing fanwise. Somewhat similar mouth-brushes are found 

 in some related, and also in some quite unrelated, forms, and are evi- 

 dently independently developed to meet the requirements of a particu- 

 lar mode of life. 



Pupa. — The pupae of all the families are short and stout, and 

 those that I have examined present a wide diversity of characters. 

 In Simuliidae we find the pupae partly enclosed in cocoons, the struc- 

 ture of which varies somewhat with the species, and in the pupae of 

 all species of the family the respiratory organs consist of a number of 

 slender filaments attached to a common base on each side of thorax 

 anteriorly. The abdomen is armed with short spines in transverse 

 series, which aid in retaining a hold upon the surface of the cocoon. 

 Scatopsidae, or at least the species known to me, differ in having the 

 pupa free, the thoracic respiratory organs furcate, and the abdomen 

 without spines, but with the spiracles elevated. Bibionidae have 

 neither elevated thoracic respiratory organs nor abdominal spines, and 

 show a more primitive structure throughout. The pupae of all the 

 families have the legs straight — a character which readily separates 

 them from the pupae of the chironomid and culicid groups. 



Imago. — Antennae 8- to 12-jointed; eyes of male sometimes 

 contiguous above and with the facets of the upper half much larger 

 than those of the lower; eyes of female separated; ocelli present or 

 absent ; proboscis short, in part chitinized in Simuliidae. Wings large, 

 the veins of the anterior portion much stronger than those of the 

 posterior ; posterior cross-vein never present. 



Family BIBIONIDAE 



The larvae which I have examined differ from those of every 

 other family I have seen in three particulars : the false segment behind 



