TROMOPTERA 471 



small cross-vein is prominently present ; anal cell always long and con- 

 tracted or closed near the hindmargin ; ambient vein complete. Squam?e 

 (both alar and thoracal) small or at the utmost moderate in size, but 

 occasionally {Toxophora) with remarkably long fringes. 



The perfect insects are never very large and never very small ; they 

 are essentially aerial, and the Bomhylidce possess a hovering power which 

 is developed sometimes to a most remarkable degree, while the Thercvida: 

 are very active and the males sometimes execute frantic aerial dances. 

 They are essentially sun-lovers and never blood-suckers, and though the 

 T]ierevid(c are reputedly " Kobber-Flies " the statement requires confirma- 

 tion. The larvae are parasitic and (as far as is known) have two very 

 distinct stages of development in the Bomhylidcc, the mobile one after 

 hatching and the torpid one after reaching their intended host, while in 

 the Thcrevidm they are very active in their earlier stages. 



The Tkomoptera are easily distinguished from the EREMOCHyETA by 

 the presence of only two pad-like pulvilli, and usually by the presence of 

 distinct bristles on the thorax and legs ; even when these bristles are 

 absent still spicules and an apical circlet of spines exist on the tibise, and 

 usually the spicules or spines beneath the hind femora are of a stronger 

 nature than those which occur in any EKEMOCHiETA. The Dermatina 

 are distinguished by their remarkable absence of pubescence and bristles, 

 by their pedestrian heavily built legs, by their different antenna?, and by 

 the totally distinct system of venation in which the discal vein always ends 

 before the wing-tip. The Energofoda (certainly in the Asilidcc) possess 

 strong stout bristles on the thorax and legs, or at any rate have 

 coarse dense pubescence in place thereof, and are essentially pedestrian 

 and predaceous species apparently without any powers of hovering * or 

 dancing. 



The Tromoptera (in the sense adopted by me) include only the 

 Bomhylidcc and Thcrevidm, but in the sense of the founder (Osten Sacken) 

 included the Nemcstrinidce, Cyrtidcv, and Sccnojnnidcr. The reason for 

 Osten Sacken's inclusion of the first two of these families lay in the stress 

 which he placed in the aerial habits of the superfamily, while I have been 

 more impressed by the structural characters afforded by the total absence 

 of bristles and the presence of three pad-like pulvilli and consequently 

 have included them in the Eremoch^ta. As regards the Sccnopinidm it 

 is probable that Osten Sacken himself would not have included them in 

 his Tromoptera, but placed them there in association with the Therevidm 

 "according to the received opinion." 



Osten Sacken's words (Berl. ent. Zeitschr., 1896, p. 368) in connection 

 with the founding of the Superfamily Tromoptera are worthy of quota- 

 tion, but it must be borne in mind that he included the Ncmestrinidce, 

 Cyrtidce, and Scenopinidce. 



* Colonel Yerbury informs me that be has seen the male of a species of Promachus (or some allied genus) 

 hovering over the female vphen courting. 



