48 Tachinidae. 



almost no apical cross-vein is formed. From the angle may issne a 

 branch or prolongation of the discai vein, either only as a fold, more 

 or less darkened, or as a real shorter or longer veinlet. In a few cases 

 the apical cross-vein may be more or less to quite obliterated, the 

 discai vein then not reaching the margin. The lower branch of the 

 postical vein hes at base beneath the postical cross-vein and goes 

 rectangularly down to the anal vein, so that it is like a cross-vein, 

 and the anal cell is short. The anal vein does not reach the margin 

 except in rare cases {Bucentes and species of Actia^ Hypoderma). 

 Axillary vein more or less distinct. Costa shows two more or less 

 visible interruptions, one a little behind hiimeral cross-vein, the 

 other just at end of mediastinal vein. At the base of the cubital vein 

 there is nearly always a few bristles on both sides of the wing, some- 

 times the bristles on upper side stretch longer out to nearly the 

 whole length, and in some cases also subcostal and postical vein 

 may bear bristles. Alula well developed, generally rather large. — 

 Squamulæ large, the lower by far the largest and often very large; 

 only in Rhinophorinae it is somewhat reduced, the inner margin 

 bending away from scutellum and the squamula being somewhat 

 narrow and elongate, reminding of the shape in Coenosia. At the 

 margin the squamulæ are quite short-haired or with longer hairs 

 only at base on outer side; they are generally bare on upper surface, 

 only in a few cases haired. 



The development of the Tachinidae is rather well known and 

 has been much studied on account of their importance for the forestry 

 and also on account of the biologicai interest connected with the 

 study of these parasitic flies. The larvæ are in general cylindrical 

 or elongated oval; those of the Sarcophaginae and Calliphorinae are 

 more of the common Muscid shape, elongated conical, tapering 

 anteriorly, cut behind. As all cyclorrhaphous larvæ they have three 

 stages, separated by two moults (in Gastrophilus there seems to be 

 four and in Hypoderma (lineatiim and bovis) five stages, see Boas: 

 Hestebremserne, Tidskr. f. Veterinær. 2, XXI, Laake: Journ. of 

 Agric. Research XXI, 1921 and XXVIII, 1924 and Bishoff, Laake, 

 Brundrett and Wells: U. S. Dep. of Agric, Depart. Bull. 1369, 1926). The 

 larva consists of twelve segments, the head included. Above the mouth 

 opening are two small antennæ-like organs, consisting of the more or 

 less fused antennæ and maxillary palpi. In the first stage they have 

 one, in the later stages two mouth hooks sitting on a pharyngeal 

 skeleton. They are, as other cyclorrhaphous larvæ, amphipneustic, 



