245 



much the same manner as do those of Mycetophilidae, hiding away 

 in chinks in the bark of trees, and frequently feigning death when dis- 

 turbed. They are much more active than Rhyphus and generally shun 

 the light, whereas the latter do not appear to do so. The food con- 

 sists of exuding sap of trees. 



Tribe Eucephala 



I have retained in this tribe, which is one of those proposed by 

 Brauer, three superfamilies, removing Bibionoidea to Oligoneura. 

 The tribe contains an assemblage of families that show a consid- 

 erable range of variation in the structure of practically all parts of the 

 body in the larvae, but these all possess a complete head with opposed 

 mandibles and usually a well-developed labium. The antennae are 

 usually well developed, consisting in Chironomidae of four to six 

 joints, but in Mycetophiloidea, exclusive of Bolitophilidae, these 

 organs are rudimentary, being usually very slightly elevated clear 

 spots, contrasting sharply with the dark color of the remainder 

 of the head. Peripneustic forms are present in Bolitophilidae, 

 Mycetophilidae, Sciaridae, and Chironomidae, while some of the other 

 families contain species that have rudimentary abdominal spiracles. I 

 have decided upon the present grouping of the genera after a consider- 

 ation of the characters of all the stages. This arrangement is quite 

 different from that outlined by de Meijere* in a paper that appeared 

 when my manuscript was almost completed. I am not dogmatic with 

 regard to my arrangement of the families concerned, and it should 

 prove interesting to students to compare the results as presented in 

 the two papers. 



As this paper is primarily intended as a handbook for the ready 

 identification of immature forms of Diptera and not as a discussion of 

 affinities, it is deemed inadmissible to bolster the classification suggest- 

 ed by lengthy argumentation. The proving or disproving of the sug- 

 gested affinities is left to the future, and probably to other students. 



In order to locate species of the tribe it is necessary to make use 

 of the keys to the various stages of Nematocera on a previous page. 



The structure and habits of the species are dealt with under the 

 family, subfamily, or generic headings. 



*Zool. Jahrb., Abt. f. System. Geog. u. Biol., Vol. 40, Pt. 3-4, 1916, p. 307. 



