EFFECT OF INFRA RED 407 



NATURAL CONDITIONS UNDER WHICH Mermis subnigrescens 



DEPOSITS ITS EGGS 



At Woods Hole, Mass., U. S. A., on July 28, 1928, from long before 

 daylight up to 10 o'clock A.M. the weather was warm and showery. 

 The showers were gentle but subcontinuous, with light-intervals 

 between; i.e., during two or three brief intervals the sunlight actually 

 came through the fog and clouds rather clearly. 



Two full-grown female specimens of M . subnigrescens, very much 

 alike, were found depositing eggs naturally on grass etc. in an experi- 

 ment field. As each nema still contained a good many eggs, both 

 were taken to the laboratory in cold tap-water, and both subjected to 

 radiant heat of low frequency, emanating from hot steel. The results 

 of three trials on one of the nemas and four on the other were quite 

 consistent. 



An ordinary steel file about nine inches long and three-fourths of an 

 inch wide was heated until hot, though not red. As near as could be 

 judged the temperature of the file during the trials was from 400-500 

 C. The hot steel was held within an inch and a half to two inches of 

 the nemas. Held at this distance from one's cheek, it caused an 

 agreeable warm sensation; no disagreeable sensation of heat, how- 

 ever/ no suggestion of scorching. 



When the nemas were brought into the laboratory, both were still 

 slowly depositing eggs; one, however, very slowly, putting out only 

 one or two eggs semi-occasionally. When one of these ten-centimeter 

 nemas in this laboring condition was removed from water and stretched 

 out on a broad-leaf plantain, Plantago major, and the hot file brought 

 near, she immediately responded by increased rapidity of movement, 

 and in from ten to twenty seconds became coiled, sometimes rather 

 closely, so that the entire space occupied by her would not be over 

 fifteen to twenty millimeters across. Barely enough water was used 

 on the plantain leaf so that only at her points of contact with the leaf 

 was she in contact also with water. Doubtless the warmth may have 

 caused the water to evaporate a trifle more rapidly, notwithstanding 

 the saturated condition of the atmosphere, and one cannot say that 

 this change in rate of evaporation may not have had some effect on- the 

 behavior, but the inevitable inference is that the "radiant heat" caused 

 the change in behavior, corroborating, in a reverse way, experiments of 

 previous years with direct sunlight and sunlight passed through 

 heat-diminishing screens (both green glass and living foliage). 



