AKGYKAMCEBA. 99 



Anthrax) ; it is more protruding, sometimes quite large, and hanging outside of the 

 abdomen ; its structure is for this reason more apparent, and the ascertaining of the 

 sex of a specimen more easy here than in the other genera. 2. The structure of the 

 ovipositor of the female, the orifice of which is protected by those silky converging 

 fibres that distinguish the ovipositors of Lomatia, Bombylius, &c. 3. The shape of the 

 antennal style, which is bisected by a distinct suture ; this character, as I will presently 

 show, is perhaps the most important distinctive mark of the genus. 4. The shape of 

 the front legs; the tibiae beset with spinules (not smooth as in most species of 

 Exoprosopa) ; the tarsi with distinct joints, beset with spinules at the tip; ungues 

 comparatively large (in Exoprosopa the joints are indistinct, the ungues very small, 

 &c.) ; in the male the front tarsi are generally longer and more slender than in the 

 female. 5. The face is short, not protruding, rather withdrawn ; the proboscis with- 

 drawn within the mouth, with spongy lips. 



The basal joints of the antennae are very short. The third joint has in most cases the 

 shape of a short cone, or of a flattened onion, prolonged into a more or less long 

 slender style ; this style has a distinct suture in the middle, and the relative length of 

 the two portions of the style affords in some cases a useful specific character. Some- 

 times the stout basal portion of the third joint is more elongate, more gradually 

 attenuate, with a short pencil-bearing style at the end, thus showing that the portion 

 of the style before the suture, in the ordinary Argyramoebce, is nothing but a portion of 

 the third joint, and that the style beyond the suture alone is homologous to the style 

 of Exoprosopa (compare the antennae of A. hetrusca and of A. cephus, described by me 

 in the ' Western Diptera,' p. 242 ; I have no specimens of this latter species now 

 before me). This structure, the bisection of the antennal style, is perhaps the most 

 important character of the genus. Schiner, who made a very happy hit in introducing 

 the genus Argyramoeba, overlooked it, and hence did not fully grasp the limits of his own 

 genus. This is proved by the passage in ' Fauna Austr. Dipt.' i. p. 50, footnote, " that 

 if subsequent investigations revealed the presence of a pencil of hairs at the end of the 

 antennae of Anthrax velutina it should be transferred to the genus Argyramoeba" 

 Anthrax velutina has an undivided, filiform style ; the front legs and the structure of 

 both male and female genitals different from those of Argyramoeba ; it belongs to the 

 subgenus Anthrax, within the definition adopted by me in the present work. 



The prge-alar hook peculiar to the ' Anthracina ' exists here too, but is rather small. 

 The ungues are comparatively large, curved, without tooth at the base ; the pulvilli 

 large. 



The prevailing colour of the body is more or less black, often with white spots on 

 the abdomen ; the male in some species has the last segments of the abdomen silvery, 

 while the female is altogether black. The wings are variegated with black in different 

 ways ; often the antero-proximal portion is deep black, with a distinct boundary sepa- 

 rating it from the postero-distal portion, which is pure hyaline. It is worthy of notice 



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