258 



The Orders of Insects 



larvae live in decaying vegetable matter. The family is widely 

 distributed. 



Culicidae. — The CuHcida or Gnats are distinguished from the 

 preceding families by the w^ell-developed wing-neuration ; seven 

 longitudinal nervures are present, several of v/hich are forked, and 

 there are cross-nervules in the middle region of the wing-area. The 

 body, the wings and the very slender legs are hairy and scaly (fig. 9, 

 g, h). The long feelers have fifteen segments which are clothed 

 with whorled hairs, those of the male being very long and dense (fig. 

 9, H). The jaws are greatly elongated in some genera — -such as 

 Culex which includes the common gnats and mosquitoes — and the 

 sharp, horny mandibles and hypopharynx of the females can inflict a 

 severe bite on the mammals whose blood they suck ; in the male of 

 these insects the palps are remarkably long and hairy. The larvs 

 live in water; they are active grubs with large head and thorax and 

 slender flexible hind-body, by the lashing of which they swim quickly 

 through the water (fig. 72 j). They usually hang head downwards 

 from the surface, taking in air through a special tube which branches 

 from the hinder end of the body and is guarded by a valve of leaf-like 

 plates. The incomplete pupa (fig. 72) breathes through a pair of 

 respiratory tubes on the prothorax ; the openings of these rest in 

 contact with the surface as the pupa floats freely (170). The Culicidae 

 are world-wide in their range. 



Tipulidae. — The TipuHJie or Crane-flies ("Daddy-long-legs") are 

 easily distinguished from all other Nematocera by their large size, 

 their exceedingly long legs, their wings with the longitudinal 

 nervures all present and mostly forked and with numerous cross- 

 nervules, and by a distinct transverse suture across the mesoscutum. 

 The head is prominent and rounded, without simple eyes ; the 

 feelers have from six to nine segments. The hind-body is long, 

 cylindrical or spindle-shaped with seven or eight visible segments, with 

 prominent claspers in the male and ovipositor in the female. The 

 larvjE of the typical Crane-flies ( TipuUna^ in which the terminal segment 

 of the palp is long and whip-shaped) are stout, tough-skinned grubs 

 (" leather-jackets ") which live underground and feed on roots ; the 

 pupa partially raises itself out of the ground to allow the fly to emerge. 

 Among the Llmnobiina; (distinguished from the Tipulinx by the ter- 

 minal palpal segment being shorter than the last but one as well as by 

 neurational details) several genera have aquatic larv^. The Crane-flies 

 are numerous in genera and species, and are found throughout the world. 

 Rhyphidae. — -The Rhyphidte are a small family of flies distinguished 

 from the Tipulids by the absence of the suture across the mesoscutum, 

 and from all other families of Nematocera by the presence of a dis- 

 coidal cell in the wing area, formed by a cross-nervule between the 

 two median nervures towards the wing margin. The larvae feed on 

 decayinjj;- vegetable matter. The family only includes a single genus 

 of which one species {^Rhijphus fenestralis) is not uncommonly found on 

 the windows of houses. 



