292 



PRODUCTION OF RACES AND SPECIES IN LEPTINOTARSA. 



although of the same parents, do not show these changes. It also appears 

 that both structural and physiological characteristics are modified by this 

 process. 



During the last three years I have been able to experiment with the tropical 

 members of the genus, and although the work is as yet in its earliest stages 

 and very incomplete, the results obtained thus far support and extend those 

 found in decemlineata. Of these I shall give only a few of the clearest and 

 best worked out series, reserving until a future date a more elaborate pre- 

 sentation of this line of experimentation. 



EXPERIMENTS WITH L. MULTIT^NIATA. 



My experiments with this species cover the short period of three years, and 

 are now being continued. From specimens obtained at Guadalupe, Federal 

 District, Mexico, in August, 1903, a generation was reared at Chicago in Sep- 

 tember and October of 1903, which hibernated until February, 1904. This 

 generation was to all appearances normal. From this material 6 males and 



1 

 11 



in 



IV 



v 



VI 



MULTIT/ENIATA 

 62$, J 1109 



MULTIT/ENIATA 

 61 S< 



(From Guadalupe. D. F. Mexico, 1003. 



(Reared at Chicago iu September and October, 

 6 O (after aestivation subjected to conditions described. 



MULTIT/ENIATA 

 42 <?, I 45? 



M' 



MULTIT/ENIATA 

 46 <J, I 479 



MULTIT/ENIATA 

 32 $ , I 61 9 



MULTIT/ENIATA 



MULTIT/ENIATA 

 6$, I 49 



'{ 



MULTIT/ENIATA 

 21 c?. I 29 9 



MULTIT/ENIATA 

 40 <J, | 32 9 



: 'i 



MELANOTHORAX 

 20 g, I 29 9 



MELANOTHORAX 

 33 , I 37$ 



MELANOTHORAX 

 44 $, I 40 9 



MELANOTHORAX 



MULTIT/ENIATA 



? ? 



All killed in late larval and early pupal 6tages 



TEXT-FIGTJRE 2S. 



6 females were taken and subjected to conditions in which the relative humid- 

 ity was ioo per cent and the average temperature 30 C both considerably 

 above the normal condition for the species. The beetles were kept in this for 

 one-half the reproductive cycle, and then transferred to normal conditions. 

 During the period of changed condition 492 eggs were laid and 509 eggs in 

 the second period. These were reared in normal conditions, and there came 

 from the first lot 59 beetles, of which there were 10 normal beetles, 6 males 

 and 4 females, and 49 of the form melanothorax, 20 males and 29 females. 

 From the second lot of eggs came 82 normal beetles. These lots were now 

 continued and reared, giving in successive generations pure forms without 

 traces of reversion. All the lots went through the regular cycle of two 

 generations, and then hibernated for six weeks, and after emerging from 

 aestivation, began reproduction, but were killed in July, 1904. The data of 

 the experiment in diagrammatic form is given in text-figure 28. 



