DURHAM DIPTERA. 205 



XXVIII. 318. 



9 (6). Abdominal bows isolated and not extending over the 

 side margins; wings usually with a dark splash 

 near the costa after the middle. 



10 (11). All legs entirely yellow. (162 1. festivum, L.) 



11 (10). Fore femora black about the base. 



(1622. vernale, Lw.) 



12 (5). Abdomen with two "golden bows" more conspicuous 



than the others. 



1623. Chrysotoxum bicinctum, L. 

 Hesleden, 2 $ , 2, 30-8-99. 



320. Microdon, Mg. 



The larva? of this genus are extraordinary slug-like creatures 

 (VII. 13). They have been found in colonies of Formica 

 fusca and under loose willow bark. The flies frequent damp 

 places, under leaves and in grass. 



1 (2). Scutellum orange. ( r 5 2 5« mutabilis, L.) 



2 (1). Scutellum blackish green. 



3 (4). Legs mostly yellow ; frons narrow ; thorax with a 



patch of black hairs between the wings. 



(1626. devius, L.) 



4 (3). Legs mostly dark brown ; frons broad ; thoracic patch 



of black hairs absent. (1627. latifrons, Lw.) 



Family XXIX.— CONOPID^E. 



The known larva? are parasitic on Hymenoptera and 

 Orthoptera. 



TABLE OP GENERA AND SPECIES. 



1 (14). Third antennal joint with a short terminal style ; 



ocelli absent. 



Sub-Family Conopin^e. 



2 (11). Femora not abnormally thickened at the base ; second 



abdominal segment not remarkably narrower and 

 longer than the others. 



