Therevidae. 133 



Metapleura with long hairs. Abdomen consisting of seven not trans- 

 formed segments; it is generally somewhat long, conical {Exapata has 

 a short, broad abdomen). Legs somewhat long, slender, provided 

 with stronger or weaker bristles. All tibiæ with apical spurs. Glaws 

 not strong: two pulvilli but no empodium. Wings with the costal 

 vein extending all round the margin; the cubital vein forked, thus 

 two cubital cells ; the discai cell formed exclusively 'of the discai vein, 

 between it and the upper branch of the postical vein a postical cross- 

 vein; three veins issuing from the discai cell; five posterior cells, the 

 fourth more or less narrowly open or closed near the margin. Alula 

 well developed ; squamula alaris developed with a short fringe at the 

 margin, squamula thoracalis not developed but the frenulum distinet, 

 broad towards the angulus. In rest the wings are borne somewhat, 

 more or less open, in some species very slightly open, nearly parallel. 



The larvæ are elongate, vermiform, cylindrical and pointed towards 

 each end. The body apparently consists, with the head included, of 

 twenty segments on account of a number (7) of segment-like parts 

 formed by the chitinised connecting membrane — intermediate seg- 

 ments — interpolated between the abdominal segments. The head 

 is small, chitinised, not retractile; the mouth parts consist of a median 

 labrum, small, hook-shaped mandibles and somewhat soft maxillæ 

 with a palpus; there are small antennal papillæ, but no eyes. The 

 larvæ are amphipneustic with prothoracic spiracles and a posterior 

 pair lying apparently on the last segment but two. — The pupa is 

 free; it has the antennal sheaths lying on the front side of the head, 

 directed to each side. The thorax has on each side a strong bristle 

 or thin spine, and the abdominal segments have girdles of long bristles; 

 the last segment terminates in a somewhat long, thin, at the apex 

 bifid spine, 



The larvæ live in the earth or sand, sometimes also in dung, in 

 decaying wood or in fungi; they are carnivorous and devour other 

 larvæ; the pupæ are found at the same piaces as the larvæ. 



The Therevids are medium sized flies; they occur in thickets and 

 bushes and in low herbage ; they are most often seen sitting on the 

 leaves. They are generally thought to be predaceous. 



Of the family 89 species are known from the palæarctic region 

 and 76 species from North America; none is known to be common 

 to both regions, 



I am acquainted with no case of parasitic Hymenoptera on 

 Therevids. 



Therevids earlier recorded from Denmark: — Kramer (Spec. Insectol. 

 Dan. 1760) records one species, Musca piebeja; Briinniche (Prodr. 



