AKGTEAM(EBA. 215 



etc. ; (5) the fore tibiae are beset with spinules ; the tarsi have 

 distinct joints, the ungues are I'ather large ; in the 6 the front 

 tarsi are generally longer and more slender than in the § ; (6) the 

 knee-shaped basal angle of the 2nd longitudinal vein and the fork 

 of the 3rd vein generally each bear a short appendix directed 

 backwards. 



The basal antennal joints are very slioi-t, the 3rd short, cone- 

 shaped, or flattened onion-shaped, bearing a more or less slender 

 but distinct style, which is bisected about its middle, the relative 

 lengths of the proximal and apical portions being often a good 

 specific character. 



"Sometimes the stout basal portion of the 3rd 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 Argyrumcebce is nothing but a portion 

 of the 3rd joint, and that the style beyond the suture alone is 

 homologous to the style of Exoprosopa" (Osten-SacJcen). 



Range. World-wide, except Australasia. 



Life-history. The larva of one European species, A. trifasciata, 

 Mg., feeds on the larva of a mason-bee {Chalicodoma), to which it 

 has to find its way through any small crack or gap in the masonry, 

 after which it undergoes a complete change of form. The pupa 

 is provided with special apparatus for penetrating the masonry 

 to escape.* 



Table of Species. 



1. Anal cell closed gentilis, Brim., p. 230. 



Anal cell open 2. 



2. Wings very dark blackish brown at base, 



the colour diminishing distally and poste- 

 riorly, but the lightest part of the wing 



at least pale brown bipunctata, F., p. 217. 



Wings always with some clear surface, 

 with or without various markings 3. 



3. Wings with distinct baso-costal oblique 



band, with or without isolated spots .... 4. 

 Wings without distinct baso-costal oblique 



band 10. 



4. Wings with isolated spots on the clear part 5. 

 Wings without such isolated spots 6. 



5. Distal margin of dark wing-band limited 



to enclosing anterior cross-vein and bases 

 of discal and 4th posterior cells ; spot on 

 fork of 2nd vein and that at base of 

 3rd pcsterior cell quite isolated from the 

 band itself and of some size ; spot at 

 base of 2nd posterior cell small, indi.«tinct 

 or absent distiyma, Wd., p. 218. 



* An excellent tr.inslation of Fabi-e's description is given by Dr. Sharp 

 (Cainb. Nat. Hist., Insect?, pt. ii, p. 486) and by Verrall ( 'British Flies,' v,p.475). 



