Diptera: Nemocera vera^ N. anomala and Eremochaeta. 425 



The relationship of these two sections of fhe Nem. vera towards 

 each other, the difference in the larvae notwithstanding, is well ex- 

 pressed in tlieir general appearance, and in the analogous striicture 

 of their heads, ej'es and antennae. (In the next chapter of this paper 

 we shall have the opportunity to study these characters and affini- 

 ties in greater detail.) 



The Nemocera anomala are distinguished by sonie characters 

 which never appear among the Neniocera vera. Thus holoptic heads 

 occur here, not only in the male (Bibio, Rhyphus, Simidiiai^), 

 but also in both sexes (OrphnepMla and some Blepharoceridae) . 

 The eyes are offen bisected, the facets upon the npper side being 

 larger; these two halves of the eyes are sometimes bicolored (Si- 

 imdwmj, or they are separated by a distinct groove, or even by a 

 transverse unfacetted stripe (Blepharocera, male Bibio). The an- 

 tennae do not show, on the joints of the flagellum, those aggregations 

 of hairs in verticils and pencils, which I have called sensitive 

 hairs, and which are peculiar to the Nemocera vera. Three very 

 distinct ocelli occur in the Blepharoceridae, Bibionidae and BJiy- 

 phidae\ they are wanting in the Simididae and Orj^hnephilidae. 

 The empodia and pulvilli, in some genera, have an uncoramon de- 

 velopment; the legs are sometimes particularly strong {Bibio, Di- 

 loplius, Simulium); the sexes, in these same three genera, are rc- 

 markably diiferentiated in their whole appearance. The number of 

 genera in these families is small (only a Single one in the Simididae 

 and Orphnephilidae, three in the Rhyphidae, and about eight in 

 each of the two other families); the number of species in these ge- 

 nera in most cases is likewise small (except in the Bibionidae and 

 Siimdidae). A certain nionotony prevails, in forms and coloürs, 

 within the same genus, notwithstanding an extensive, sometimes spo- 

 radic, geographica! distribution ; the metamorphoses are also peculiar. 

 At the same time it is a significant fact that just like the Limnobina 

 anomala among the Tiptdidae, the Nemocera anomala seem to 

 represent archaic forms, remains of bygone entomological horizons. 



There must have been an age when the type of structure of the 

 Nemocera anomala, combining filiform palpi and filiform antennae 

 with holoptic heads and developed pulvilli, was more abundantly re- 

 presented than it is now. What remains at present of that type are 

 the cosmopolitan Bibionidae, Simnlidae and Khyphus; also Orphne- 

 pMla, which may be considered as cosmopolitan, as it has been 

 already found in different parts of P^urope, as well as in North and 

 South America. The only genera of this group which have a narrow 

 gcographical ränge are Pachyneura from Lapland, and the paradoxical 



