49 2 DIPTERA CHAP. 



been said to suck blood from Vertebrates, but this appears to be 

 erroneous. The metamorphoses of a few species have been ob- 

 served. Ferris has called attention to the close alliance between 

 the larvae of Tabanidae and of Asilidae, 1 and it seems at present 

 impossible to draw a line of distinction between the two. So 

 far as is known, the larvae of Asilidae are terrestrial and 

 predaceous, attacking more particularly the larvae of Coleoptera, 

 into which they sometimes bore ; in Laphria there are numerous 

 pseudopods, somewhat of the kind shown in Fig. 230, but less 

 perfect and without hairs ; the head and breathing organs appear 

 to be very different. According to Beling's descriptions of the 

 larvae of Asilus, the head in this case is more like that of the 

 figure, but there are no pseudopods. The flies of Asilidae and 

 Tabanidae are so very distinct that these resemblances between 

 their larvae are worthy of note. 



Fam. 25. Apioceridae. Moderate-sized flies marked with Hack 

 and ivhite, with an appearance like that of some Muscidae and 

 Asilidae ; with clear wings, the veins not deeply coloured ; antennae 

 short, with a short, simple appendage ; no empodium. But little 

 is known as to the flies of this family, of which only two genera, 

 consisting of about a dozen species, are found in North America, 

 Chili, and Australia. Osten Sacken is inclined to treat them 

 as an aberrant division of Asilidae. Brauer looks on them as 

 primitive or synthetic forms of much interest, and has briefly 

 described a larva which he considers may be that of Apiocera, 

 but this is doubtful ; it is a twenty-segmented form, and may be 

 that of a Thereva. 2 



Fam. 26. Empidae. Small or moderate-sized flies of obscure 

 colours, grey, rusty, or black, with small head, somewhat globular 

 in form, with three-jointed antennae, the terminal joint long and 

 pointed ; usually there is a long slender beak ; the legs are elongate, 

 frequently hairy ; the tarsi bear long pulvilli and a small em- 

 podium. The Empidae are an extensive family of flies, with 

 predaceous habits, the rostrum being used by the female as 

 an instrument for impaling and sucking other flies. They are 

 occasionally very numerous in individuals, especially in wooded 

 districts. There is great variety ; there are nearly "200 species 

 in Britain. The forms placed in the sub-family Hybotinae are 

 curious slender little Insects, with very convex thorax and 

 1 Ann. Soc. ent. France (4) x. 1870, p. 221. 2 SB. Ak. Wien, xci. 1885, p. 392. 



