314 WILLIAM LAWRENCE TOWER. 



an isolated standard locality in the valley of Mexico south of 

 Guadalupe, were placed on an isolated island in the Balsas River. 

 This island was fairly well covered with a growth of Solanum 

 rostratum, or a closely related form, upon which all three 

 species would feed. As far as could be discovered, the island 

 was devoid of any individuals of L. oblongata which occur very 

 sparingly in that general region, and the neighboring banks of 

 the river and the islands were all searched, but they afforded no 

 trace of L. oblongata. These introduced beetles were allowed to 

 breed and gave the first hybrid generation in August, 1905. In 

 this generation only the adults were seen, and of the adults we 

 could recognize definitely five forms: 



(A) Those which on inspection appeared to be wholly L. decem- 

 lineata; (B) those which appeared to be wholly L. oblongata; 

 and (C) those which appeared to be wholly L. multitmniata. 

 There were individuals which were manifestly intermediate hy- 

 brids, in form, punctation and coloration, between L. decem- 

 lineata and L. oblongata (D) ; and between L. decemlineata and 

 L. multitcBniata (E). Of these five forms a census was made 

 with the following results : 



All the individuals were allowed to remain in the colony and 

 interbred freely in August, giving early in September a second 

 generation, of which the following census was made: 



D 



loi I 90 I 1,292 



These hibernated during the winter of 1905-1906, and were not 

 seen again until September, 1906, in the fourth hybrid generation 

 of the culture. At this time the dominant form was manifestly 

 a combination between L. decemlineata, L. oblongata and L. 

 multitceniata , with the oblongata-decemlineata attributes in excess 

 of those of L. multitceniata. (A combination between classes D 

 and E of Fj and F2.) 



