254 '1 he Descent I'f Man. Paht II 



It IS liardly woitt wliile saying anything abont the propoi-tion oi 

 the sexes in certain spei-ies afl even groups of insects, for the males 

 are unknown or very rai-e, ami the females are partbenogeuetic, that 

 is, fertile with ut sexual union ; examples of this are attbrded by 

 several of the Cynipida;.*" lu all the gall-making Cynipidse known 

 to Mr. Wiilbli, the females are four ur five times as numerous as the 

 males ; and so it is, as he informs me, with the fiall-maliiny- Cec.domyiiss 

 'Diptera). With some common tpecies of Saw-flies (Teiitliredinae) 

 Mr. F. Smith has reared hundreds of specimens from larviu of all 

 sizes, but has never reared a single male : on the other hand, Curtis 

 says,*" that with certain species (Alhalia), bred by him, the m: les were 

 ti ) the females as six to one ; whilst exactly the reverse occurred with 

 (he mature insects "f the same species caught in the fields. In the 

 laiiiily of Bees, Hermann Miiller," collected a large number of 

 siieciiufus of many s|.ecics, and reared others from ti.e cocojiis, and 

 counted the sexes. He found that the males of some spei-ies gieatly 

 exceeded the females in number ; in others the reverse occurred ; and 

 in others the two sexes were nearly equal. But as in most oases the 

 males emerge from the cocoons before the females, ihey are at the 

 cnmmeiicemeut of the breeding season practically in excess. Miillei' 

 also ob. erved that the relative number of the two sexes in some 

 species differed much in d.fferent localities. But as H. Miiller has 

 himself remarked to me, these remarks must be received with 

 some caution, as one sex might more easily escape observation tlian 

 the other. Thus his broliber Fritz Miiller has noticed in Brazil that 

 the two sexes of the same species of bee sometimes frequent different 

 kinds of flowers. With respect to the Orthoptera, I know hardly 

 auylhiiif!; about the relative number of the sexe^: Korte,*' howe\er, 

 says that out of 500 locusts which he examine;!, the males wei-e t.o 

 ihe females as five to six. With the Neuroptera, Mr. Wal.-h states 

 that in many, but by no means in all the s-pccies of the Orion.nous 

 giou|i, theie is a great overplus of males : in the genus Hetspiina, also, 

 the males are generally at least four times as numercais as the females. 

 In certai'i species in the genus Gomphus the males are equally in 

 excess, whilst in two other species, the females are twice or thri. t; 

 as numerous as the males. In some European species of Psocus 

 thousands of females may be collected without a single male, whilst 

 with other species of tlie same genus both sexes are common.*'^ in 

 England, Mr. MacLachlan has captuied hundreds of the female 

 Apalania muUebris, but has never seen tI.e male; and of Boreus 

 hyi'mi{lis imly four or five males have been Sieii heie."° Mith m st 

 of till sc species (excepting the 'J'enthredinse) there is at prc'sent no 

 evidence that the females are subject to parthenogenesis ; and tijus we 

 Bc c how ignorant we are of tlie causes of the apparent discrepancy in 

 the proportion of the two texes. 



In tie other Classes of tlie Articulata I have been able to collect still 



•' Walsh, in 'The American En- derheuschrecke,' 1828, p. 20. 



tornologist,' vol. i. 1869, p. 103. " ' Observatimis on X. American 



f. Sniitli, ' Kiicord of Zoologica.' Neuroptera,' by H. Hagen and B. 0. 



Uttrattire,' 18li7, p. 3'i8. \\'al.<h, ' Proc. Ent. Soc. Phila- 



" ' Farm Insects,' pp. 45^6. delphia,' Oct. 1803, pp. 168, 223, 



"^ *AnwenJung der Darwinschen 239. 



Lchri' Vcrh. d. a. V. Jahrg. i.viv.' " 'Proc. Ent. Soc. London, Fob 



"' 'liie .Strich, Zuo- oder Wan- 17,1868. 



