SUPERNUMERARY CHROMOSOMES IN DIABROTICA. 



pected to affect the somatic characteristics of the insects. If, 

 however, i he supernumeraries of Diabrotica come originally from 

 different regi< >ns - >f A', there would seem to be no reason why they 

 should not bear functional genes for sex and other characters. 

 The in. ile alv. 'in. tins A" so far as my experience goes (over 



700 male- , but one would suppose, if the supernumeraries are 

 functional in heredity, that one A' and a supernumerary might 

 frequently deii-niiim- the development of a female, and if so 

 there -hould be males without A', but with a supernumerary 

 in its place, h may. of course, be true that the abnormal di\ i-i-ui 

 V pp-dii- in. -up. inumeraries in itself indicates a de-.-iu-rati- 

 or non-functional condition of that particular A' chromosome, 

 and ther. its progeny the resulting stipernuinera< 



This \\uiild tall in line with Schleip's ('ll) s ' :n in regard 



i" the rejected A" chromosome in the spcrmato-em -sis of the 

 lieniiaphiodi ration of .-1 n^iostomum nigru .. that it 



had ahead\ bec< une non-functional at an earlier stage, \\ hence its 

 later beha\ior. It is exceedingly desirable that the female sex 

 elU of il <>ticas should be studied, but I ha\e not been 



able i ni\' favorable mitoses in the adults, or to secure 



lar\ .e oi pupa- I r oin the soil or roots of plants on u hit h they live. 

 N-\eral attempts to breed them have given no iv-uli-,. 



Tin u males each having one supernumerary \\ere 



studied from the point of view of tin- division of the super- 

 numerarie- in the first maturation mitosis. All anaph.tses and 

 metapha-es in each preparation were examined and all cases 

 \\lure it \\.is possible to determine the position and beha\ior of 

 the sii].ernnmerar\' reconled. In the metapha-i- the super- 

 numerary \\as in the equatorial plate in 5} i p< r cent, of <oi 

 cases and out of the j)late nearer one pole of the spindle in 



45.0 per cent. Apparently the supernumeraries, \\lnn they 

 di\ide. do ~o later than the bivalent chromosome-., so all ana- 

 phases \\ere examined on this point. In 55.6 per cent, of the 

 anapha-es found in the 12 testes, the supernumerary was ],e- 

 t \\een the daughter plates, and in 44 percent, it was di\ filing or 

 di\ filed. Here the 56.6 per cent, corresponds closely with the 



54.1 per cent, in the equatorial plato in the metaphase, and the 

 44.4 per cent, outside of the daughter plates in anaph.ises comes 



