CHAPTER VII 



DIPTERA OR FLIES ; APHANIPTERA- OR FLEAS ; THYSAXOPTERA 



OR THRIPS 



Order VII. Diptera 



Wings two, membranous, usually transparent and never very lar;/< ; 

 behind the wings a pair of small erect capitate bodies 

 li alteres frequently concealed under membranous hoods. 

 No distinct prothorax, all the divisions of the thorax being 

 united to form a large mass. Mouth-parts very variable, 

 formed for suction not for biting, frequently assuming the 

 form of a proboscis that can be retracted and concealed in a 

 cleft of the under side of the head. The metamorphosis is 

 very great, the larvae bearing no resemblance whatever to the 

 perfect Insects, but being usually footless grubs or maggots ; 

 frequently the head is indistinct, small, and retracted. 

 Pupa variable, either exposed and rather hard, with the 

 appendages of the body more or less adherent ; or enclosed 

 in a scaly capsule looking like a seed, and when extracted, 

 soft and delicate, with the appendages not fastened to the 

 body incapable of movement. 



THIS definition of the Diptera, or two-winged flies, is framed 

 without reference to the fleas, which are wingless, or to a few 

 other parasitic wingless Diptera, such as the sheep-tick. Although 

 the Order is of enormous extent, these exceptional cases are 

 remarkably few. About 40,000 species of Diptera have been 

 discovered, but these are only a tithe of what are still unknown 

 to science. The Order is not a favourite one with entomologists, 

 and by the rest of the world it may be said to be detested. 

 Flies do not display the sort of intelligence we appreciate, 



