SOMATIC MUTATIONS AND ELYTRAL MOSAICS OF 



BRUCHUS. 



J. K. BREITENBECHER, 



Contribution from the Zoological Laboratory of the University of Oklahoma, 



Second Series, No. 10. 



INTRODUCTION. 



During the years 1918 to 1920 thirty-one unusual females were 

 discovered in cultures of Bruchus quadrimaculatus* These un- 

 usual types were normal insects except that the elytra were of 

 different colors. Such striking differences as these constitute what 

 the geneticists term mosaics, and because they appear in the elytra 

 the author describes them as elytral mosaics. It is a noteworthy 

 fact, proven by the experiments, that these mosaics are not trans- 

 mitted ; it is necessary, therefore, to assume that these peculiar 

 differences must originate in somatic tissue. It will be evident 

 from the experiment, described herein, that these mosaics manifest 

 an order of dominance in agreement with that of mutations. The 

 author, therefore, concludes that these elytral mosaics are caused 

 by somatic mutations. 



It is also a noteworthy fact that these mosaics were more abun- 

 dantly manifested during the period in .which the author was in- 

 vestigating the genetics of the first three mutants (red, black, and 

 white) which he had discovered in the progeny of the so-called 

 " four-spotted cowpea-weevil," Bruchus quadrhnaculatus Fabr. 

 In a previous paper (Breitenbecher, '21) the behavior of these 

 mutants was described and a multiple allelomorph system demon- 

 strated for the factors which involve the four-body and elytral 

 colors as discovered previously for Bntclnis. Here the author 

 proved that the order of dominance for these four-color factors 

 was red, black, white, and tan (the wild type). The females and 

 males of the wild type have tan elytra and bodies, while the females 



* Since this paper was sent to press, 17 new mosaics have been observed, 

 making a total of 48 to date. 



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