26 DEPARTMENT BULLETIN 779. 



quently results in the concentration of 6 or 8 individuals on one 

 grain head while similar plants in the vicinity receive but slight 

 attention from the species. When large numbers of the insects are 

 present in fields of wide area the adults appear to concentrate in 

 certain portions of the field and change their location as the food 

 supply becomes exhausted. 



It is problematical whether this gregarious habit exhibited by the 

 grain bug is a result of an attraction between the individuals or is 

 largely stimulated by the presence of attractive food during its period 

 of feeding and by superior facilities for Drotection during its inactive 

 periods. 



FLIGHT. 



Generally the adults are very sluggish flyers and their flight is 

 limited to a short distance. When disturbed they habitually drop to 

 the ground for the purpose of seeking concealment without attempt- 

 ing flight. Under special conditions, however, the adults are capable 

 of long and sustained flight. On June 30, 1916, large numbers of the 

 adults were, present on a small plot of wheat growing in the insectary 

 grounds at Maxwell. The day was very warm, with no wind, and' 

 at this time when disturbed the adults took to flight and gradually 

 ascended to a height of from 10 to 30 feet in the air, from this altitude 

 maintaining a straight course as far as the eye could follow. Similar 

 observations have been made in the field from time to time, and it is 

 probable that these migrations generally are traceable to the need of 

 a fresh food supply. 



The adults have not been observed in flight during windy days, but 

 the fact that they commonly migrate to the leeward side of the field 

 at these times would indicate that their general line of flight was in 

 the same direction as the prevailing wind. 



On October 2, 1916, during a windy period, large numbers of 

 adults were found feeding on the Russian thistle growing in the 

 northeast corner of an abandoned wheat field. The wind was from 

 the southwest, and although the adults were found in small numbers 

 throughout the field, most of them apparently had been driven to 

 their present location by the prevailing wind. 



HIBERNATION. « 



The grain bug hibernates exclusively in the adult stage. No im- 

 mature forms have been observed to survive the winter, although 

 many of the larger nymphs enter hibernation with the adults and 

 live for a short time. 



LOCATION OF HIBERNATING QTJABTEBS. 



In general, ChlorocJiroa sayi hibernates under and among dead 

 weeds or rubbish, in crevices under the loose bark of trees or posts, 



