Biology of the Membra cidae of the Cayuga Lake Basin 411 



For comparison of the results of variation in moisture the summers 

 of 1913 and 1914 may serve as excellent extremes. The summer of 1913 

 was the occasion of the worst drought that has been experienced in this 

 locality for many years. Vegetation suffered greatly and the United 

 States Weather Bureau reported that all recent records were broken 

 for lack of rainfall at the Ithaca station. The spring of 1914, on the other 

 hand, was marked by unusual precipitation and the early part of the 

 summer was very wet. The dates of hatching of the first eggs of Vanduzea 

 arquata for these two seasons, together with the number of broods for 

 the years, may be tabulated as follows: 



Vanduzea arqunta 1913 1914 



Eggs hatched May 15 April 26 



Second-brood eggs laid July 2 June 5 



Third-brood eggs laid September 16 July 18 



Fourth-brood eggs laid : None September 20 



In the same seasons the variations in the nymphal periods of Ceresa 



dkeros were as follows: 



Ceresa dicer os 1913 1914 



First instar 5-7 days 8-10 days 



Second instar 5-8 8-9 



Third instar 6-7 7-9 



Fourth instar 9 10-12 



Fifth instar 12-14 14-18 



Total 37-45 days 47-58 days 



From these figures it would appear that the hatching of the eggs and 

 the development of the n;^anphs are retarded by dry weather and accelerated 

 by abundance of moisture. As a natural result the number of broods 

 is reduced ui dry weather. This may be due to the condition of the 

 vegetation during the favorable and unfavorable seasons, and it seems 

 probable that the relationship between the insects and their hosts gives 

 rise to complicated problems. In connection with the subject of moisture 

 conditions it may be recalled that Ball (1915) has reported the fact that 

 in arid regions Vanduzea vestita Godg., Caynpylenchia curvata Fabr., 

 and Publilia modesta Uhler have the habit of burrowing in the soil around 

 the roots of the host plant as a protection against the smi and the dry 

 air. In the Cayuga Lake Basin, where of course such conditions never 

 prevail, the amount of moisture has no effect on the adult insect so far as 

 has been observed. 



