210 TROPICAL MEDICINE AND HYGIENE 



causes of cutaneous and intestinal myiasis, and also all 

 as mechanical carriers of disease, especially the common 

 house-fly and other Muscidae (in a general sense). 



The characters of the spine or arista at the base of the 

 third joint of the antennae and variations in the fourth 

 longitudinal vein enable the group to be subdivided into* 

 several families. 



The more important are : 



(1) Anthomyidffi. Arista plumose to tip ; first posterior cell open 



(fig. 87) ; large squamae, and eyes in male contiguous. 



(2) Muscida (in restricted sense). Arista plumose to tip; no 



bristles on abdomen except at tip ; first posterior cell more 

 or less narrow at apex (fig. 88) ; abdomen, four visible 

 segments. 



(3) Sarcophagida. Arista plumose in part only ; tip always bare ; 



thorax usually light and dark stripes, and abdomen marbled 

 in the same colour. 



(4) Tachinidtz. Arista bare ; abdomen hairy, often with spines ; 



squamae very large. 



(5) CEstrida. Head large, lower part swollen ; arista usually bare; 



ocelli present, mouth-parts ill-developed, often rudimentary. 



Mefonofum 



(After Williston.) 



FIG. 89. i, 2, 3, indicate first, second, and third pair 01 legs; Meso. t 

 mesopleura ; Sterno., sternopleura ; Ptero.^ pteropleura ; Meta.^ metapleura ; 

 Hypo. , hypopleura. The presence or absence of hairs on this last is of great 

 importance and enables the important genus Musca to be separated from other 

 genera. 



The first four of these used to be all included under 

 Muscidae, and are sometimes now grouped together as 

 the super-family Muscoidea. 



