750 CLASS IV. INSECTA. 



decaying matter (Sepsis) or in cheese and fat (Piophila). The cheese 

 skipper is the larva of P. casei. They also injure dried and smoked meat. 

 Fam. 40. Chloropidae (Oscinidae). The larvae live in the stems of 

 wheat and grass and do much damage, or mine in the leaves of such plants 

 as the beet-root ; others act as scavengers. In the autumn the images 

 sometimes turn up in countless swarms, usually in the same building at 

 intervals of some years. They are amongst the commonest insects to 

 get into eyes whether of man or beasts. The Frit-fly, Oscinis frit, and the 

 Gout-fly, Chlorops taeniopus, are well known corn pests. 

 Fam. 41. Ulidiidae. 

 Fam. 42. Platystomidae. 



Fam. 43. Ephydridae. Some of this family breeds in salt lakes such 

 as those of Utah, and a few occur in urinals. They exist in vast 

 numbers in many of the Mexican lakes, where both the larvae and flies 

 drift in heaps on to the shores and are collected by the Indians and made 

 into palatable cakes. 



Fam. 44. Helomyzidae. Dark, small flies frequenting the shade and 

 twilight, laying their eggs in animal dejecta or amongst fungi. 

 Fam. 45. Dryomyzidae. 



Fam. 46. Borboridae. Small, dark flies with clear wings. Some 

 species of Borborus, which is a British genus, are however wingless. They 

 breed in dung and have some use as scavengers. 



Fam. 47. Phycodromidae. Small greyish flies with a darker abdomen. 

 They occur on the beaches of both seas and lakes and seem to breed 

 amongst the vegetable jetsam. 

 Fam. 48. Thyreophoridae. 



Fam. 49. Seatophagidae (Scatomyzidae). Moderate-sized, slender 

 flies, frequently hairy. They breed in the dung of various animals and 

 are generally known as dung-flies. 



Fam. 50. Geomyzidae. A small family of small flies whose larvae, 

 in the cases known, mine in the leaves of grass and corn. 



Fam. 51. Drosophilidae. Small flies which haunt decaying fruit, etc., 

 in which their larvae live. They also occur in tinned fruits and in pickles 

 and amongst the refuse of cider- and wine-presses. Drosophila. 



Fam. 52. Psilidae. These generally dark flies are met with on the leaves 

 of bushes and undergrowth. The larvae, when known, burrow in plant- 

 stems or in fleshy roots. Psila rosae causes the disease of "rust" in 

 carrots. 



Fam. 53. Micropezidae (Tanypezidae). Moderate-sized, slender flies 

 with long legs which frequent decaying matter both animal and vegetable. 

 Their larvae are unknown. 



Fam. 54. Trypetidae, Fruit-flies. Spotted yellow or brown flies with 

 mottled wings. The larvae live in galls on the stems or fruits of plants. 

 In America Trypeta pomonella does much harm to apples, as does Ceratitis 

 capitata to peaches. 



Fam. 55. Sapromyzidae. Wings rarely spotted. The larvae some- 

 times live under bark or in the tunnels bored in wood by other insects 

 or in rotten vegetation. 



Fam. 56. Lonchaeidae. This family is often included in the preceding. 

 Its larvae have been found in stems and roots and in dung. Lonchaea. 

 Fam. 57. Rhopalomeridae. 



Fam. 58. Ortalidae. Usually metallic flies with spotted or -striped 

 wings. The larvae occur under the bark of certain trees and in fruit, but 



