Mr Lamb, Male secondary characters in the Diptera 475 



An unusual type of male secondarif characters in the Diftera. By 

 D. G. Lamb, M.A. 



[Read 16 May 1921.] 



Secondary sexual characters may be classed as persistent or 

 sporadic: the former occur with much regularity throughout a 

 genus or family, the latter crop up suddenly in isolated species 

 of a genus, and are often similar in form in quite unrelated famihes. 

 Examples of the persistent type are the antennal dimorphism of 

 so many nematocerous and other famihes, and the male eye 

 holopticism in many famihes. The sporadic types are such as: (1) 

 frontal processes as in Ceratitis sp., (2) very varied types of leg 

 adornment, which is a common form, probably connected with 

 courting habits, (3) replacement of head bristles by hair tufts as 

 on some Chrysosomatinae, (4) costal lumps as in the two quite 

 unrelated species, Pemphigonotus mirahilis (Chloropids) and Omma- 

 lius Lema (Asilids), (5) differences in the palpal structure, as in 

 many Dohchopids and others. The hst could be extended, but one 

 thing is apparent, all the characters of either type are peripheral in 

 their position on the insect. 



I The author has recently completed the study of certain famihes 

 of flies contained in the collections made by Dr H. Scott in the 



I Seychelles, the descriptions of which will appear in a forthcoming 



I volume of the Percv Sladen Expeditions Reports, Trans. Lmn. 



\Soc. London, Ser. 2, ZooL, vol. 18. Amongst these are some 

 exceedingly interesting forms belonging to the Dohchopodidae. 

 These belong to a new genus, Craterophorus, which is probably to 

 be referred to the subfamily Chrysosomatinae; these differ from 

 other known species of fly in having centrally placed secondary 

 characters; further each of the three species constituting the genus 

 bears the same set of characters, one of which is nearly unique, 

 the others being absolutely so. The genus is apparently endemic, 



. being found in the native forests of the Island of Mahe. There 

 are no tarsal or antennal differences between the sexes. The 

 special characters under consideration are four in number: (1) the 

 Aving of the male (Fig. 1) is quite different in shape from that of 

 the female (Fig. 2) having a sharply angled posterior margin; this 

 peculiar form of wing is almost if not quite unique. The other three 



I characters are more strictly central; they are shown m the photo- 

 graph (Fig. 3) and diagram (Fig. 4), these characters are as follows: 

 (2) the Dohchopodidae are usually devoid of alulae, but m these 

 species one is developed though it is of a totally exceptional form. 



