ESTIVATION AND HIBERNATION. 245 



HABITS AND INSTINCTS CONNECTED WITH HIBERNATION AND 



AESTIVATION. 



As has been shown in the preceding section, all Leptinotarsas either hiber- 

 nate or sestivate in each alternating generation. This phenomenon is one of 

 importance in the life cycle of each species, as it occurs in that portion of the 

 year when conditions of existence are least favorable. As far as is known, all 

 of the species in the genus are in this dormant state for at least three months 

 of the year, and the larger portion of them for five or more months. Hiber- 

 nation and aestivation are fundamentally one and the same process, the term 

 hibernation being applied to the dormant period produced by lowered temper- 

 atures, and aestivation to that which follows the coming on of the dry season 

 in the warmer parts of the earth. There is, I believe, no reason for the exist- 

 ence of two terms to describe this phenomenon, as both apply to the same 

 physiological process, the only difference being that found in the factors which 

 initiate them. In this paper I shall use them as the synonymous terms, which 

 they really are, and we shall see later that in these beetles the two processes 

 are the same. 



Throughout the whole of the United States, after the second brood of 

 decemlineata has emerged in late September or early October, it devours a 

 large amount of food in the first few days of its adult life, and stores up in the 

 fat body a reserve supply to be used in the ensuing period of hibernation and 

 in starting the germ cell onward in development in the spring. This storing 

 up of food accomplished, the beetles stop feeding, and the preparations for 

 hibernation are begun. This is initiated by the emptying of the alimentary 

 canal of all food and the elimination by the malpighian tubules of the excess- 

 ive quantity of waste products. These are often red, as they are at pupation. 

 This clearing out of the alimentary canal and the elimination from the body of 

 as much of the waste of metabolism as is possible requires from three to as 

 many as ten days for its accomplishment, it being effected rapidly in warm, 

 clear weather, and retarded in cold or cloudy weather. The beetles now no 

 longer pass the nights upon the plants, but late in the afternoon, as the sun's 

 rays become more and more slanting, they are found burrowing into the 

 ground, often to a depth of 3 or 4 inches, where they remain until the next 

 morning, crawling out again when the sun's rays have warmed the earth ; and 

 if the day be cool the beetles do not come out in any numbers, and may even 

 remain in the ground for several days if the temperature is constantly rather 

 low. 



After the contents of the alimentary canal have been emptied out and the 

 excretion of the excessive amount of waste products from the malpighian 

 tubules has commenced, the body weight begins to fall rapidly and continues 

 to do so until on the average there has been a loss of about 30 per cent of the 

 gross weight of the beetle by the beginning of preparation for hibernation. 

 This reduction in weight is occasioned by the emptying of the contents of the 



