I I Kllll.k IM-:KVATIONS ON St'PERM MF.RARY 



( IIK< M< >-< >MES. AND SEX RATIOS IN 



MABROTICA SOROR. 



X. M. STEVENS. 

 ^i Tl KM MKKARY CHROMOSOMES. 



lii iln- -iiniiiHT iif 1910 while I was enjoying the privile. 

 .nnl ho-pii,ility uf ihf Marine Biological Laboratory at I. a Julia. 

 < 'alifornia. I \<>k advantage of the opportunity to study the 

 malt 'o-rin cell- of Diabrotica soror from a new locality, Ilaxini; 

 pn-\ iou-lv >und suj>ernumerary chromosomes \ar\in^ 



in uuiiil.iT fi .in one to five in about 50 per cent, of the male 

 individuals of Diabrotica soror at Mountain View. < 'aliti nia. 

 and /'. a 12-punctata at Bryn Mawr, I'a., I \\a inten --led 



\\ln-ther sujK-rnuineraries would be found in ilu- >aine 

 pr-'piinimi in a third locality. 



Pestes IK-HI a hundred individuals were studii-d in aceto- 

 (aimiiH pn paratimi-. The greater part of the mati-rial \\a- 

 ciillrct-d in a corn-field in the open country between 1. a Julia 

 and tin new laboratory which is two miles north t tin- town. 

 A h u \\in- "litainrd from a rose-garden in La Joll.i .iiid one lot 

 o| os m.,1, -, .mil females was collecteil for me \>\ Mi-- M\nU- 

 |<'liii^<ni on (..MI in a gardi-n at National < itv, ju^t -omh of 

 San l>i(^n. lndi\ idual records were kept for earh loi. Imt the 



i'iiditi.iii- \\iih respect to number of supernumeraries pn\ed to 

 l-e aliout the same for the three collecting Around-.. 



To m\ .-nrpii-e I found supernumeraries scarce. In the tir-i 

 J5 male- examinrd, Ji had no supernumeraries and 4 one; while 

 out <.f tin- lu-t 25 examined the same >ummer at Mountain 

 \'ie\\ 15 had no supernumerary, 7 one and ; two; and in the 

 tir-t 25 at Mountain View in 1909, there \\.-n i ^ with no super- 

 numerary, ') with one, 2 with two and i \\iih three. In the 

 I. a Jolla material the 89th individual was n-.irhed before a 

 of two supernumeraries was met with, and in the first 100 

 male> ;() had no supernumerary, 20 one, and I two. The follow- 

 er 



