24 



DEPARTMENT BULLETIN 779. 



the sunlight is reflected from the dorsal surfaces of the insects and 

 adds to their conspicuous appearance. At this time at least 95 per 

 cent of the adults present in the vicinity may be seen without moving 

 any part of the plants. When disturbed, however, most of the adults 

 immediately drop to the ground and seek cover. 



ODOB AND EXCBEMENT. 



The characteristic odor of the adults and nymphs is not generally 

 noticeable in the field even when the insects are present in large 

 numbers. During thrashing operations, however, many farmers 

 have reported that the odor given oif by the grain bug was so 

 noticeable as to cause much discomfiture to the workers. This was 

 probably due to the fact that large numbers of the insects had con- 

 centrated about the grain shocks and had given off the offensive 

 odor when disturbed. In life-history cages this offensive odor is 

 not noticeable unless the insects are roughly handled. 



The excrement of CMorochroa sayi is a yellow-green fluid and is 

 commonly Jound on the leaves or stems of the host plant. It varies 

 in size from mere specks deposited by the young nymphs to circular 

 masses 5 millimeters in diameter deposited by the adults. 



DAILY ACTIVITY. 



During the calm, pleasant weather of the summer months the adults 

 of CMorochroa sayi are active and feeding throughout the greater 

 part of the day and night. They are not affected by the excessive 

 heat of midday, as is true of the njnnphs, but are more active and 

 do most of their feeding while high temperatures prevail. (See 

 Table VIII.) During periods of high winds, rain, or hail storms 

 and nightly temperatures below 60°, the insects cease their activities 

 and seek shelter, generally under some object on the ground or around 

 the bases of their food plants. 



Table VIII. — Daily activity and feeding habits of adults of CMorochroa sayi, 



July 15, 1916. 



Wire cage 3 by 3 by 3 feet over wheat plot — 2 male and 4 female adults. 



Hour. 



Temperature. 



Shade. 



Sun. 



°F. 



°F. 



63 





62 





62 





64 





69 





69 





72 





73 





Weather conditions. 



Observation on activity. 



A. M. 



4 



4.30 







5.30 



6 



6.30 



7 



7.30 



•Oloudy 



Sunrise; cloudy 

 jcioudy 



Partly cloudy. . 

 Jcioudy 



5 on heads in same po- 

 sition as at 9 p. m. last 

 night; at least 2 have 

 seta3 inserted into grain 

 head. 

 Do. 



4 resting. 



'4 resting. 



2 resting. 



3 resting. 

 ' Do. 



,3 resting and feeding. 



