TRACHEATA 373 



long slender legs. The mesonotum bears a V-shaped mark, 

 and the abdomen is long and cylindrical. Their larvae burrow 

 underground, and do considerable damage to crops by gnawing 

 roots, etc. They are known as leather-jackets, and are of a 

 whitish-brown colour and grub-like appearance. Tipula oleracea, 

 T. maculosa, and T. paludosa are all common English species. 



Family Ceoidomyiidae (gall-flies). — This is a family of 

 small Diptera, which give rise to galls in plants. Their wings 

 have few nervures, usually three longitudinal ones ; they are 

 rounded at their free ends ; the point of attachment is, how- 

 ever, very narrow. The antennae have numerous joints, and 

 are moniliform. The proboscis is short and the legs long. The 

 females have a well-developed ovipositor, by means of which they 

 puncture some plant and deposit their egg therein. This in 

 some cases gives rise to a gall, in which the larvae develope. 

 The pupa stage may also be undergone in the gaU, or it may 



Fig. 210. — Cecidmiyia destructor 

 (the Hessian-fly). 



1. Insect. 



2. Larva. 



3. Pupa or "flax seed.", 



All magnified. 



be free. The larvae of some of the Cecidomyias produce 

 parthenogenetic ova, from which young are born, a phenomenon 

 known as paedogenesis. Cecidomyia destructor is the well- 

 known Hessian-fly. C. salicis produces galls on willows. 



Family Tabanidae (horse-flies). — Tabanus is the horse-fly, 

 a large Dipterous insect. The male does not bite, but lives on 

 the nectar of flowers. The bite of the female, however, is 

 very painful and poisonous. Cases have been recorded of horses 

 on the prairies being worried to death by these insects. The 

 larvae of Tabanus are said to live upon snails, those of allied 

 genera live in water. 



Family BOMBYLIIDAE. — Very hairy flies, swift in flight, 



