some I'artlienojcntlic (Jliiiuiioiiiitl;i'. 223 



Those, 1 believe, are the only cases so far ph'iced on record 

 of the occurrence of parthenofjjeiicsis in this fjiiiiily of the 

 Diptera ; hut 1 am now ahU' to a(hl two others. 



Chironomus r/avaticrus, Kiefl'er. 

 (Tdni/far.ius /If.iilis, 1^uihi>, ? Linn(5.) 



Durinfj the month of May 1917 I collected sonic weeds 

 and nuul from a pond at Letchworth, Herts, in the hope of 

 heinj; able to discover the hirvie of certain (.'ulicidie, hut was 

 then only able tt) rear various species of ('hirononii(he from 

 the material. Amon^ these were a ntinibcr of speciinens of 

 a spt'cifs which I (htcrmined Inter us ('/liruiioinini c/(U'a/i<-rns, 

 KicH". (Hull. Soc. Nat. Hist. Mctz, xxviii. I'Jl.'i, p. 17). My 

 interest in these was aroused in the Hrst place by the fact 

 that this very distinctively marked species had not been 

 recorded from Britain, and was (juite unrepresented in the 

 eollci'tions at the Hritisji Museum ami at Cambridf^e. 

 Seeondly, it was noticeable that all the specimens wiiich 

 hatched (aljout forty) were femak's. Suspecting that this 

 might be a case of parthenogenesis, I isolated a few pupie in 

 a small closed receptacle. Two females hatched, and each 

 of these deposited an egg-mass. From these eggs larv;e 

 devclopj.'d whicli produced female adults on August 10; eggs 

 were laiil ijarthenogcnetieally on Aug. IS, and |)rodnecil 

 larv;e on August 2'3. These for the most i)art died young, 

 owing, 1 believe, to lack of Ibod ; a few lived through the 

 winter and became full-grown in June 1918, but for some 

 reason unknown to me no adults hatched from them. 



1 made a diligent search by sweeping with a net in the 

 n(ighl)ourhood of the pond where the larvie were obtained, 

 but suceceded in tinding only female specimens, and am 

 inclined to believe that in this locality at least no males 

 occur. It is interesting to note that the species was origi- 

 nally (leseribed by KicHer from females only, reared from 

 larvie by Thieniunann. It was also reared by Reaumur 

 from larvie collected near Paris ; he ligures the larva and 

 the female adult (Hist, Ins. iii. p. 179, pi. xiv. figs. 11-16). 

 No other records of the adult of ('. clavaticrus have been 

 UKide, and the species is thus known only in the female sex 

 at present. 



The discovery of the male — supposing it to exist — would 

 be a .matter ot some interest, sincx* it minht give a furtlu-r 

 clue to the correct generic position of the species. From 

 the characters of the adult female alone, ami particularly on 

 account of the cntirdv hire wings Kictter was no doubt 



