366 C. R. Osten Sachen: 



derivation is analogous to that of the Greek word „iQ>]fioy.6fii]i'\ de- 

 prived of liair), characterized by tlie absolute want of macrochaetae, 

 by the prcdoininance of holoptic hoads in the male sex, by the pre- 

 sence, in most cases, of three pulvilli and of five posterior cells, 

 by the more or less distinct developnient of the posterior squamae 

 (which do not exist in the Nemocera), and by other charaeters. 

 The larvae of this Superfamily belong to a peculiar type, called the 

 long-headed larvae (Marno).') 



After separating the J^remochaeta (1891), as a Superfamily, 

 from the rest of the Orthorrhapha Brachycera, I attempted the 

 grouping of the remaining families of this Suborder. All these fa- 

 milies, with the exception of the Mydaidae, Cyrtidae and Ncme- 

 sirinidae, are chaetophora, as I called them in 1884, that is, 

 macrochaetae-bearing. I found confirmed, in this case, some gene- 

 ralizations concerning the distribution of the macrochaetae, whicb I 

 had foreshadowed in that same year (Essay of comparative Chaeto- 

 taxy, Trans. Ent. Soc. London, 1884, p. 500 — 501). Such gene- 

 ralizations are: 



1) That among aerial Diptera, macrochaetae are scarce, while 

 among the pedestrian Diptera they are abnndant. 2) That the 

 aerial Diptera show a distinct prevalence of holoptic heads, 

 which is generally connected with power of hovering (in the Essay 

 I called it poisiug). The pedestrian Diptera, on the contrary 

 have, for the most part, dichoptic mal es, or, at least i)seudo- 

 holoptic oncs, as I wonld call some of thom (for instance those of 

 some JRwpidae; the ex))lanation will be givcn inimediately). .'!) Tiiat 

 the aerial Diptera, in consequcnce of tlioir mode of lifo, have weaker 

 legs, of simple structure,-) principally fit for alighting, and are usu- 

 ally provided with peculiar ada])tations in the venation. The i)e- 

 destrian Diptera use the legs not for alighting only, but for rnnning, 



^) My papor in the Berl. Ent. Z. 1892 has the words to be con- 

 liniied at tlio end (p. 46G), because I intended to piiblish on Ihe J^re- 

 mocliaeta as dotailed a sfatement as I had done for the Nemocera. 

 'l'he paper was in an advanced state of preparation, bnt I postponed 

 its publication for the purpose of a betler study of the aiicestral 

 forms, so abnndant in that Superfamily. I have not found in Mu- 

 seums as nnuch as I expected, and so, from one postponernent to the 

 other, the paper remained unpublished lo this day. I still hope to see 

 its coniplelion and publication. 



-) Tlie use of the legs for cleansing (head, wings etc.) and the 

 adaptations for that end, are, I suppose, common to all Diptera (sniall 

 bristles, or spinules on the legs, cspecially the tibiae), and for this rea- 

 son are taken for granted in my text. 



