Diptera 257 



composed of eight to twelve segments. The compound eyes are 

 large, in the male occupying most of the head-area ; there are three 

 simple eyes. The wings are broad, with six longitudinal nervures 

 and only one or two cross-nervules ; the legs are short and stout, 

 the shins having often large spines, and the feet three terminal pads. 

 The larv2 are somewhat flattened and spindle-shaped maggots, the 

 body-segments bearing tubercles and bristles; they feed on roots of 

 living plants or in decaying vegetable matter. Most of the Bibionidz 

 are dull black in colour. 



Siniuliidae. — The SimuIUJa or Sand- midges are a small family 

 comprising only a single genus (Simulium). The head is partly over- 

 hung by the thorax ; the compound eyes of the male are enormous 

 and globular, but there are no simple eyes, and the eleven-segmented 

 feelers are thick and only slightly longer than the head. The wings 

 are relatively large with seven longitudinal nervures but only a 

 single cross-nervule; the legs are stout and unarmed. The upper 

 lip of the female is developed as a hard piercer, and tlie insects, 

 occurring in swarms in some parts of the world, cause great 

 annoyance to men and domestic animals by their attacks, as they 

 suck blood greedily. The larvs (fig. i6o, a, b) live in water, attached 

 to stones or rushes by a sucker at the tail-end. In addition to the 

 feelers and the usual jaws, the head carries a most remarkable pair 

 of jointed appendages which bear long flexible hairs; the motion of 

 these brings organic food-particles within reach of the mouth. The 

 pupa (fig. 160, f, </), has branching gill-filaments on the prothorax, 

 and rests in a pouch-shaped, silken cocoon (fig. i6o, i) (170). The 

 Simuliidi are generally distributed. 



Chironomidae. — The Chh-onomidii or Midges are distinguished 

 from the Simuliidi by their elongate feelers and legs, and narrow 

 wings ; from the Cecidomyid^ (with which they agree in the absence 

 of simple eyes i they are distinguished by the costal nervure reaching 

 only to the wing-tip. The head is small and largely hidden beneath 

 the thorax, and the feelers have from six to fifteen segments which, 

 especially in the males, bear whorls of hairs, often exceedingly long. 

 The larvse live in water ; they are long cylindrical grubs often of a 

 bright red colour '"blood-worms") with paired sucker-feet on the 

 second and last thirteenth) body-segments, and, usually, thread-like 

 gills on the eleventh and twelfth. They often form sandy tubes for 

 protection. The pupa is not enclosed in a cocoon ; it breathes by paired 

 gill-threads on the prothorax, these have the form of feathered stars. 

 The Chironomidse are w^orld-wide in their range ; several genera live 

 on the sea-shore and have marine larva: (169, 170). 



Psychodidae. — The PsychodiJa are a family of very small, densely 

 hairy, moth-like flies. The small head is almost hidden under the 

 thorax ; the feelers have sixteen segments, and there are no simple 

 eyes. Only six or seven abdominal segments are visible, but the 

 male claspers are very prominent. The wings have seven longitu- 

 dinal nervures, but the cross-nervules are all near the wing-base. The 



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