FURTHER STUDIES ON THE CHROMOSOMES OF THE 



COLEOPTERA 



BY 



N. M. STEVENS 

 With Four Plates 



In three previous papers ('05, '06, '08) the chromosomes of 

 several species of Coleoptera have been described and figured, 

 and the role of the heterochromosomes in sex determination dis- 

 cussed. The following pages are a further contribution to our 

 knowledge of the character and behavior of the heterochromo- 

 somes, and of the methods of synapsis in this order of insects. 



The methods used in handling the material have been the 

 same as in previous work: fixation with Gilson's mercuro-nitric, 

 Flemming's chromo-aceto-osmic, and Hermann's platino-aceto- 

 osmic fluids, and staining with iron haematoxylin or thionin. 

 The aceto-carmine method has been used in testing fresh material, 

 and as a check on the section method. 



PHOTINUS PENNSYLVANICUS (pAM. LAMPYRID^) 

 PHOTINUS CONSANGUINEUS (fAM. LAMPYRID^) 



In my 1906 paper on the spermatogenesis of Coleoptera and 

 other insects, the spermatogonial plate of one of the fireflies, 

 Ellychnia corrusca, was shown on PI. XIII, Fig. 236. The mate- 

 rial was obtained from adults in September at Woods Hole. Only 

 spermatogonia and growth stages of the spermatocytes were 

 present in the testes. The spermatogonial plate contains nineteen 

 chromosomes (Fig. i), two V's, two long rods and fifteen shorter 

 rods. Constancy in form made this material seem very favorable 

 for study of the individuality of the chromosomes, but I have 

 not been able to get the maturation stages. Two other fireflies 



The Journal of Experimental Zoology, vol. vi, no. i. 



