1920.] 135 



posterior angles. These depressions are more sharply defined than the similar 

 depressed areas in I, indujacea. Length 6^ mm. 



Hal. Basilan (C. F. Baiter: 11908). 



Closely allied to /. incligacea Pasc. but differing in colour and in 

 the uniformly dark antennae. From /. hasalis Waterh., from Java, 

 which has similarly bicolorous elytra and dark antennae, it differs in its 

 larger size, in the testaceous colour of the fore part of the body, and in 

 the deep blue instead of brown apical half of the elytra. 



2. Isclialia philijjpinus, sp. n. 



Upper side testaceotis, with a broad spear-shaped sulural brown patch on 

 tlie elytra which reaches neither the base nor the apex. Under side of 

 pro- and mesothora.v testaceous, of metathorax and abdomen piceous Avith a 

 (lark blue metallic tint ; antennae and legs piceous, the former almost black, 

 both with slight dark blue metallic reflexions. Thorax campanulate, the sides 

 not angulate in the middle. Length 6^ mm. 



Rah. Mt. Makiling, Luzon (C. F. Baker: 6035). 



Closely allied to /. dimidiata in structure, differing chiefly^ in colour 

 and in the shape of the thoi-ax, the disc of the latter with vaguely defined 

 impressions similar to those of I. indigacea. 



April ISith, 1920. 



DIMORPHISM IN THE ANTENNAE OF A MALE MIDGE. 

 BY F. W. EDWARDS, B.A., F.E.S. 



JDimorpbic males are of very rare occurrence in the Diptera,* even 

 among those species which have strongly-developed secondary sexual 

 characters. The following case, which has recently come under my 

 notice, may therefore be of some interest. 



The species concerned is Trichocladius ephippium Zett. (Cr/'cofopus 

 ephippium of YerralFs List of British Diptera), a Chironomid tly which 

 is found abundantly in all parts of Britain. It occurs in great numbers 

 by the river Ivel at Kadwell, Herts, and I have frequently collected 

 normal males and females there. As is usual in this subfamily, the 

 males have 14-jointed strongly plumose antennae, while the females 

 have them shorter, 7-jointed, and with only a few short hairs; the 

 basal joint is smaller than in the male, and the followuig joints bear 

 special " taste-bristles." 



* ExHmpleB are to be found in certain Sciarinae (.Pnyxia seabiet), the males of which have 

 dimorphic wings : another possible case is Kieffer's Forcipoiiiyiri Ae/erocera, described froni a male 

 with antennae reeembling ttiose of a female. The eye-stalks ol Ackiat are variable in lenjjth but not 

 truly dimori'liic. 



