1908] Biological Notes on Potato Beetle 169 



before going into hibernation, and there appears to be no reason 

 wh}^ the larvae so produced should not have reached maturity with 

 ease. It seems perfectly reasonable to me to have reared at least 

 three, if not four, complete cycles of this insect during the season, 

 if the breeding had been started about the first of June, instead 

 of more than three weeks later, as unfortunately was the case. 



Although the foregoing looks clear enough to me, but because 

 of the conditions being those of confinement and on so small a 

 scale, I approach with caution the statements of Tower (1906, 

 p. 243), on the number of generations in Leptinotarsa decem- 

 lineata. Quoting directly from this work, he says: "The num- 

 ber of generations in Leptinotarsa each year, in both temperate 

 and tropical latitudes, is a remarkably constant character, and 

 might well be used as a generic differential. As far as I know, the 

 number in all of the species is limited to two. Thus, there are 

 two generations throughout the range of decemlineata, although 

 Lugger has recorded three in Minnesota, and others have sup- 

 posed that there may be three in the southern United States. I 

 have not, however, been able to get decemlineata to breed more 

 than twice in a season without a period of hibernation or aestiva- 

 tion. In the spring decemlineata emerges from the ground, and 

 after a period of feeding, during which the germ-cells are also 

 maturing, it breeds and lays the eggs for the first generation. 

 These are usually all deposited at about the same time, but there 

 are always for a month or more some individuals that are laying 

 eggs, and of course the larvae and imagines resulting from these 

 eggs w^hich are last laid are much later in maturing than are the 

 majority of the population. The first brood, on emergence, feeds 

 for a few days, and then deposits the eggs for the second genera- 

 tion. The majority of these eggs hatch late in the summer, and 

 after the animals feed and fly around for a month or more they 

 burrow into the ground, and there hibernate until the following 

 spring. The second generation does not develop the germ-cells 

 nor show any reproductive activity until after it has passed 

 through a period of hibernation or aestivation. Beetles are found 

 breeding even late in the autumn, but these are the belated 

 individuals of either the first or second generation. As far as I 

 can discover, the life cycle in this species is that given above." 

 Further down on the same page, he says: "The species in the 

 genus are therefore double-brooded, the second brood undergoing 

 hibernation or aestivation before reproductive activity is re- 



