161 
1926] Notes on the Behavior of Dineutes americanus 
porary irritating sensation. Some individuals eat more than 
others. 
A darkened battery jar was used in studying the reaction 
of these insects to light. If some practicable scheme can be 
devised for covering the beetles eyes, better results will be ob- 
tained. I found that adhesives interfere with the insect for it 
usually spent its time trying to rub off the coverings, often with 
success. 
In the darkened tank the beetles remained quiet but when 
light was admitted at the surface through a small hole in the 
varnish activity ensued. The beetles swam about and tried to 
get out but showed neither positive nor negative phototropism so 
far as could be observed. Light was then admitted in a beam six 
inches below the surface. The beetles left the surface and dived 
to the point at which the light was admitted. This latter be- 
havior was also noticed when the light was admitted only through 
the lower opening. From this it is reasonable to believe that a 
stimulation of the lower eyes results in a positive phototropic 
response, while the upper pair do not show either form of photo- 
tropic response with sufficient regularity to be determined. 
A statement concerning the water line of the beetle seems 
desirable. Hatch (’25) speaks in detail of the “stream-lines” of 
the body and of its position on the water. He failed to notice 
that the shadow cast on the floor of the tank by the beetle is not 
a continuous ellipse in conformity with the shape of the body but 
that, owing to the breaking of the surface film by the swimming 
legs, the shadow really consists of two circles which indicates 
that the body of the beetle is wet only at the point where the 
swimming legs enter the water. 
References. 
Wilson, Charles B. 
’23 Waterbeetles in Relation to Pondfish Culture, with Life- 
histories of those found in Fishponds of Fairport, Iowa. 
Bull. Bur. Fisheries, Vol. XXXIX, pp. 231-345, figs. 148. 
Hatch, Melville H. 
’25 An Outline of the Ecology of Gyrinidse. Bull. Brooklyn 
Ent. Soc., Yol. XX, pp. 101-114. 
