370 C. R. Osten Sachen: 



The gi'oatest differenee betwecn the Tlierevklae and the tlirec above- 

 mentioncd normal families of Tromöptera consists in tlieir earlier 

 stagcs; however the great mobility of the larva of Thereva in hun- 

 ting for prey, favored by its Serpentine shape and tough consistency, 

 may be premonitory of the first, mobile stage of the larvae of the 

 other groups. Besides the Therevidae. the Cyrtidae also seem to 

 be comparatively frequent in N.-Z. Three species of Cyrtidae, re- 

 presenting as many genera, have been brought from that conntry. 

 One of them, Oncodes hrunneus, seems to be exceedingly common. 

 Thus, of the four families of Diptera, composing the Superfamily 

 Tromöptera^ the Therevidae and Cyrtidae seem to be much more 

 common in N.-Z. than in Europe or in North America. The Bom- 

 hylidae, on the contrary, flourishing in the rest of the world, seem 

 to be exceedingly rare in N.-Z. I have never seen a Bombylid (or 

 still less a Ncmestrinid) from N.-Z. in any coUection, and none have 

 been mentioned, as far as I know, in literature, except the tvvo spe- 

 cies oi Nevria^ in Schiner's Novara-work, qnoted as Coming from 

 Auckland, N.-Z., bnt the origin of which still requires contirmation, 

 as these is no other authority for tho locality.') Such a striking re- 

 sult, although based upon rathcr nieagre data, has its significancc, 

 the more so as both Bombylidae and Nemestrinidae are very 

 abundant in Australia. This result seems to me a potent argu- 

 ment for the opinion that the Therevidae are an ancestral form 

 among the Tromöptera. 



The Scenopinidae, according to the received opinion, may be 

 placed alongside of the Therevidae, although they are glabrous and 

 bristlelcss, while Therevae have a regulär System of macrochaetae 

 on the thorax. 



The Superfamily Eiiergopoda. The raison d'etre of this 

 group is easily found in the trausitional forms interposed between 

 its principal families. While the bulk of the Kmpidae (Empis, 

 Hhamphomyia etc.), have aerial habits and therefore pseudoholoptic 

 heads, the Tarhydromiae, Hemerodromiae, Clinocerae etc. are 

 more decidedly pedestrian (some of them hardly fly at all) and 

 therefore dichoptic heads begin to prevail among the males, and 

 thus make an approach towards the Dolichopodidae, with whom 

 thoy have many other characters in common.-) Haliday very early 



1) One of these Neiiriae has been described by Macquart from 

 Eastern Australia; the locality of the other is vaguely described by 

 Fabricius as „the Islands of tlie Pacific Ocean". 



-) Observe, fOr instance, that the eyes of the decidedly pe- 

 destrian genera of Thnpidae tcnd to greenish, like thoso of the Do/i- 

 chopodidae, while aerial Kmpidae have more reddish and brownish eyes. 



