^''iHOi" ] PROCEKDINGS OF THE NATIONAL MU.SEUM. 583 



PROPORTIONS or SEXES IN ISSUINO. 



I)c Goer recorded tlio singular fact tliat nialo i)arasitos alono were 

 l)rodu('(Ml in considorablo iiiuiilH'rs from oiu* k-af-rolliiii,^ cati-rpilhii- and 

 only females from another (Memoires, i, 58:3), antl on this as a basis 

 Kirby and Spcnco (IV, 223) conjectured tliat the ejjfjs producing; the two 

 sexes are arranged separately in the two ovaries. Unfortunately l)e 

 Geer's ol)servation has never been repeated, so far as I know, while 

 iiuiltifarious instances are recorded in which individuals of both sexes 

 have issued in varying proportions from the same host; and the propor- 

 tions are very variable even with the same species. West wood reared 

 20 males and 3(5 I'viniilva oi' J^tcroiiuilus piqxinoii from a chrysalis <tf \'nn- 

 cssa nrtien\ and Walker reared 82 males and 2(1 females of the same spe- 

 cies from a single chrysalis. Riley has reared 25 9 and 28 S specimens of 

 the same parasite from a chrysalis of PapUlo tiirnus, and 41 <? , 39 9 from 

 another. Scudder has reared 17 S , 108 9 from a (dirysalis of lUisilarchia 

 un'hi2)pus^ and the same author has reared and counted over 2,000 from 

 Picris rajxc in I-'rance (Butterflies of New I-^ngland, p. 121.">). llis 

 experience with regard to the proportion of the sexes was as follows: 

 " In almost all cases where the total luuuber was very great, the males 

 exceeded the females; as a whole the fenuiles averaged a little over 35 

 to a little over 25 males, and in only one-third the instances where (he 

 number of the females fell below the average the males outnumbered 

 them. The most excessive case was 84 males to 12 females, or 7 to I,'' 

 Of the sanu^ l)arasite Webster {Insect Life, i, 225) records a rearing of 

 G8 <J , 4 9 8i)ecimens from a chrysalis of Pnntin pmtndicc. 



With other species c<)unts have not been so fre(pient. kSc.udder 

 reared i , 70 9 specimens of Trichogramma minutissimum from five 

 Q^^>i of Papilio ulaucus. Kiley reared 12 9,8 S of Podarfrion jiKiutis 

 from a single eg^^ case of Stagniomantis Carolina, and the notes of the 

 Divisiouof Entomology show 14 9 , 1 -^ of the same species from another 

 egg case of the same host. 



Other isolated counts like this could l»e made iii iiuiiibei from the 

 biological collection of the National .Museum, but W()uld accomplisii 

 notliing beyond showing an extri'me variability in the proportiiuis of 

 sexes. Could we have an accumulation of counts of the same parasite 

 allecting the same host, with cormlinate observations such as are iiuli- 

 cated by iScudder in his remarks on rtcromalxs iniparum, interesting 

 results could without <loul)t be obtaiuj'd. His statement, for instance, 

 that in almost all cases where tlie total ninnber was very great the 

 males exceeded the females and the reverse, is well worth fhou;;ht and 

 the labor of verifying it and conducting many adtlitional counts, for it 

 ai)parently allbrds a new argunuuit to the tew who still contend that 

 sex is influenced by larval food. Tiie lunnerical relationship is, how- 

 ever, probably insignilicant, and the cases in which the males so greatly 

 l)reponderate are probably to l>e explained on the ground that these 



