SCIENTIFIC SURVEY. ;lgj^ 



in general footless, soft vermiform, ringed grubs, of a cylindrical- 

 conic form, attenuated in front, and thickened and obtuse behind, 

 with a head of variable form, furnished with two retractile hooks ; 

 the terminal segment of the body in many, and also that imme- 

 diately succeeding the head, furnished with two spiracles, in some 

 species inserted upon horn-like appendages. The pupa, which is 

 very unmature in its form, with a swollen head, is enclosed within 

 the contracted and indurated skin of the larva, which sometimes 

 assumes the form of an oval, horny exasticulate mass, but in other 

 species retains more of its former appearance." Westwood. 



Tachina is parasitic upon caterpillars, and destroys great num- 

 bers in the same way as Ichneumons. Some of them are parasitic 

 in the nests of bees. Sarcophaga, the flesh fly, is viviparous, the 

 larvae being placed upon the meat by the parent fly. 



Musca Caesar, the blue bottle, and vomitoria, the flesh fly, lay 

 their eggs also upon meat and decaying animal matter, the larvae 

 developing with great rapidity. The larvae of the House fly live 

 in dung. Antliomyia raphani is the grub that attacks the radish 

 roots. Other species live in onions, turnips, and the pulpy parts 

 of leaves, and in rotten substances and dung. The species are very 

 numerous ; they are rather small and fly feebly. 



Ortalis and allies produce galls in plants, or lay their eggs in 

 fruit, such as raspberries, &c. They are found in shady places ; 

 their wings are generally spotted. Tephritis asteris causes the 

 large swellings in the stems of tall asters. Oscinis, in Europe, 

 does great damage to cereals by laying its eggs in the flowers of 

 grain, the larva afterwards consuming the grain itself. Thus by 

 collecting heads of wheat and composite flowers and keeping them 

 in boxes, &c., these flies maybe reared, and much light thrown 

 upon their history and modes of attack. Many of these small flies, 

 like the micro-lepidoptera, are leaf-miners, and can scarcely be dis- 

 tinguished from them when in the larva state. 



Hippohoscidae, (Spider-flies.) These are small, flat-bodied flies, 

 of disgusting appearance and habits, which by their large clawed 

 legs run over the surface of quadrupeds and birds with great 

 agility, burying themselves in the fur or feathers. 



Nyderihia, or Bat-tick, is a wingless genus, with long legs and 

 a spider-like body, and has similar habits to the Hippohoscidae. 

 Mellophagus ovis is the Sheep-tick. " These singular creatures are 

 not produced from eggs, in the usual way among insects, but are 



