CHAPTER VIT 



DIPTERA OK FLIES ; AFHANIl'TEKA OK FLEAS ; THYSANOPTEKA 



OH THKIPS 



Order VII. Diptera 



Wings fv:n, memhrayious, vsvnUy transimrent and never very large ; 

 lehind the unngs a ^)«f/' of smcdl erect capitate hodics — 

 lialteres — frequently concealed under nieinbranous hoods. 

 No distinct j^'^'othorax, all the divisions of the thorax being 

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



formed for suction 7iot for biting, freciuently assuming the 



form of a p)voboscis that can be retracted and concecded in a 

 cleft of the under side of the head. The metamor])hosis is 

 very great, the larvae bearing no resemblance whatever to the 



l^erfect Insects, but being usually footless gruhs or maggots ; 



frequently the Itead is indistinct, small, and retracted. 

 Pupa variable, either exposed and rather hard, ivith the 

 appendages of the body more or less adherent ; or enclosed, 

 in a scaly cap)sidc looking like a seed-, and when extracted, 

 soft and delicate, with the app)(indages not fastened to the 

 body incapable of movement. 



Thls 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, 



