108 ILLINOIS STATE ACADEMY OF SCIENCE 



The adult is small, oval, and of a dull yellow color, hav- 

 ing the head usually distinct with an easily discerned 

 median impressed line. The side margins of the elytra 

 are lighter than other regions, and the length of the 

 beetle when metamorphosed is 4.5—6 mm. The anten- 

 nae are as long or longer than half the body, and the 

 third joint is somewhat longer than the fourth. 



FEEDING HABITS OF THE LARVAE 



Larvae were placed upon leaves of the white nymph 

 (Castalia) and upon those of the common pondweed 

 (Potomageton) to determine whether or not they would 

 feed on the foliage other than the yellow waterlily 

 (Nymphaea). Both the yellow and white lily pads oc- 

 cur in the same region on Douglas Lake, but only the 

 former were found to be eaten by thej larvae. The 

 Potomageton leaves were not touched, and in one aquar- 

 ium where the white nymph pads were placed there were 

 no evidences of the larvae feeding. In another aquar- 

 ium under observation, containing a white nymph pad, 

 the leaf was punctured but there were no evidences that 

 it had been eaten. The larvae in all of the aquaria pu- 

 pated in a relatively few days after they were placed on 

 the different kinds of leaves; although it does not fol- 

 low that the food relations were a factor in pupation. 



FEEDING HABITS OF THE ADULTS 



Three aquaria, two of which contained leaves of Poto- 

 mageton and one of white nymph, were set up on the 

 morning of July 30th. Into each of these several adult 

 beetles were introduced. In one of the two aquaria con- 

 taining Potomageton the leaves became infested with a 

 fungus growth and had not been eaten by the insects up 

 to the time that they were removed on Aug. 7th. In the 

 other aquarium containing Potomageton two of the beet- 

 les died on Aug. 13th, two more were dead Aug. 18th, 

 but the leaves up to this time had not been touched. Like- 

 wise in the aquarium in which had been placed leaves of 

 the white nymph, the beetles had failed to eat any of the 

 foliage when the experiment was discontinued on Aug. 

 20th. 



