486 



DIPT ERA 



or covered in large part ivith hair. Leys slender, clavjs small, 

 ivitJwut distinct empodiu7n, usually with only minute pulvilli. 

 Proboscis very long or moderate, ccntennae three-jointed, terminal 

 joint not distinctly divided, sometimes large, sometimes hair-lihe. 

 This is a very large family, including 1500 species, and is of 

 great importance to both naturalist and economist. Two well- 

 marked types, formerly treated as distinct families, are included in 

 it — (1) the Bombyliides with very long exserted rostrum, and 

 humped thorax; and (2) Anthracides, with a short beak, and of 

 more slender and graceful form. iS'"one of these flies are blood- 

 suckers, they frequent flowers only, and use their long rostrums in 

 a harmless manner. The members of both of these groups usually 

 have the wings ornamented with a pattern, which in Anthrax 

 is frequently very remarkable ; in both, the clothing of the body 

 is frequently variegated. Their powers of flight are very great, 

 and the hovering Bomlnjlius of early spring is endowed with an 

 unsurpassed capacity for movement, remaining perfectly still on 

 the wing, and darting off with lightning rapidity ; Anthrax is 

 also most rapid on the wing. In Britain we have but few- 

 species of Bombyliidae, but in warm and dry climates they are 

 very numerous. The life-history of these Insects was till recently 



unknown, but that of Argyro- 

 moeba {Anthrax) trifasciata has 

 been described by the French 

 naturalist, Fabre, who ascertained 

 that the species is parasitic on the 

 Mason-bee, Chcdicodoma muraria, 

 that forms nests of solid mas- 

 onry. He endeavoured to dis- 

 cover the egg, but failed ; the 

 parent -fly oviposits, it appears, 

 by merely dropping a minute 

 egg while flying over the surface 

 of the mass of masonry by which 

 the grubs of the Chalicodo^na are 

 protected. From this egg there 

 is hatched a minute delicate ver- 

 miform larva (Fig. 232, A). In 

 order to obtain its food, it is necessary for this feeble creature to 

 penetrate the masonry ; apparently a hopeless task, the animal 



Fig. 232. — Argyromoeia trifasciata. I 

 Young larva ; B, adult larva ; ( 

 pupa. Frauce. (After Fabre, 

 A, Greatly, B, C, .slightly magnified. 



