18 SOME INSECTS INJURIOUS TO TRUCK CROPS. 
stems, evidently by simply tumbling out to the ground, into which 
they crawl and attack the roots by boring in from outside. 
FOOD PLANTS AND HABITS. 
Most collectors of Coleoptera who have had opportunity to observe 
aquatic and other forms of beetles that frequent ponds and water 
courses are familiar with the fact that the genus Listronotus is to 
be found in the greatest abundance on aquatic or semiaquatic plants, 
more particularly on Sagittaria. Years ago Dr. C. M. Weed made 
observations on the present curculio and its food habits.* He 
found the larvee in seed capsules or heads, as well as in stalks, of 
the common arrow-head (Sagitiaria variabilis) and furnished some 
interesting observations on the insect’s life history. Beetles began 
to emerge September 23 (in Ohio), continuing emergence until the 
middle of October. The length of the pupal stage was determined 
as eleven days. The duration of the egg stage should be about the 
same at the same temperature, but in a high temperature in a warmer 
climate like that of Washington eggs might develop in seven days, 
while the larval stage is of only a few weeks’ duration. During the 
same year that Doctor Weed wrote of this species, the late Wilhelm 
Juelich informed me that he had found the beetles near New York 
City in the lower parts of reeds (Phragmites), near the bottoms. 
In the Bureau of Entomology we have a record of the finding of 
the larva by Mr. A. Koebele in August, 1884, in Virginia, near the 
District of Columbia, in the seed capsules of a species of Sagittaria, 
August 31. The beetles developed in great numbers, beginning 
September 22. 
It is not usual that phytophagous Coleoptera develop in so many 
portions of a plant as in the case of the present species, which exists 
as larva in the seed capsules and stalks of one plant and in the roots 
of a different plant.’ It is not probable that it would be able to live 
in portions of purely terrestrial plants other than the roots or stalks 
near the ground, because the insect evidently requires a more than 
usual degree of moisture. In other words, it is semiaquatic.? 
@ Bul. Ohio Agr. Exp. Sta., Tech. Ser., Vol. I, No. 1, pp. 10, 11, 1889. 
b Compare the writer’s observations with others on the biology of Conotrachelus 
elegans (Bul. 18, n. s., p. 94), which breeds commonly at the roots of Amaranthus 
and has been stated by others to live on hickory; since the eggs are known to be de- 
posited in rolled-up leaves of hickory, it seems probable that the beetles develop in 
some other portion of that plant than at the roots. The congeneric plum curculio 
(C. nenuphar Hbst.) not only develops in the plum and other stone fruits, but also 
in black-knot (Plowrightia morbosa). 
