THE GRAIN BUG. 27 



and around the bases of large uncut tufts of native grasses. The luxu- 

 riant growth of dead Russian thistle along irrigation ditch banks, 

 fence rows, and roadsides, as well as piles of debris in the fields or pas- 

 tures, affords ideal hibernating quarters for the insect. In cleaning 

 out any of these habitats during the spring, it is not unusual to find 

 scores of the adults concentrated within a very limited space. This 

 circumstance at once suggests a simple and effective method for con- 

 trolling the pest. 



The hibernating adults apparently lack the power to burrow be- 

 neath the surface of the soil. Generally they are found directly 

 underneath the material composing their hibernating quarters or in 

 loose material on the surface of the ground. 



MORTALITY DURING HIBERNATION. 



In some localities there is a high percentage of adult mortality 

 during hibernation. Frequently in the spring large numbers of dead 

 individuals are found grouped together with only a very few living 

 forms remaining. Under these circumstances it is probable that the 

 hibernating quarters were exposed to unusually severe conditions and 

 did not afford the contemplated protection from winter temperatures. 

 It is also possible that parasites, predators, or fungous diseases oc- 

 casionally may be responsible for the high rate of mortality. 



Under more favorable conditions for hibernation it is not uncom- 

 mon to find that among hundreds of adults at least 95 per cent have 

 survived the winter. 



Severe winters undoubtedly result in the death of a large per- 

 centage of hibernating adults and form one of the most important 

 factors in restricting destructive outbreaks of the species. 



CHANGE OF COLOR DURING HIBERNATION. 



In hibernation the adults of Chlorochroa sayi change to a green- 

 ish-pink color, quite distinct from their normal summer appearance. 

 This change is not evident in the autumn when the adults are seeking 

 their winter quarters or in the spring directly after they have 

 emerged from hibernation. Adults collected in the autumn and kept 

 active throughout the winter in a stove-heated room assumed the 

 same characteristic color as the inactive adults in outdoor hibernating 

 quarters. The specimens reverted to their normal coloration in the 

 spring. Possibly this change in the appearance of the species during 

 the summer and winter seasons may serve as protective coloration. 



The winter coloration persists in the pinned museum specimens of 

 adults collected from hibernation. 



