LIFE HISTORY AND HABITS OF THE 

 NORTHERN CORN ROOT- WORM 



(Diabrotica longicornis Say) 

 STEPHEN A. FORBES, State Entomologist 



The life history of the common corn root-worm was established 

 many years ago in its main features ; and for a generation it has been 

 commonly known that prompt rotation of crops is a complete preven- 

 tive of the injuries of this insect to corn. Our knowledge of the 

 subject is, however, still very deficient in detail, and the data of this 

 paper, gathered from the miscellaneous observations and operations 

 of several years, will help in some small measure to make good this 

 defect. 



Breeding Experiments. — Experiment 3054. A large number of 

 longicornis beetles collected from corn fields near Elliot, Ford county, 

 August 28, 1906, were confined, two days later, within large lantern 

 chimneys of glass, closed above by cheese-cloth, and placed upon earth 

 in flower-pots at my office insectary, in Urbana, where they were 

 kept supplied with young growing corn and flowers of the thistle as 

 food. The pots were first nearly filled with earth, and over this a 

 cloth was closely fitted, and covered with a thin layer of soil. The 

 object of this arrangement was to make it convenient to find any eggs 

 that might be laid or larvae that might hatch from them. A few eggs 

 were found, in fact, in one of these pots September 13 — enough to 

 show that the conditions were correct and that the provisions made 

 were sufficient for our purpose. The pots were kept during the winter 

 in the cold wing of the insectary under natural conditions, except that 

 they were sheltered from storms. 



May 10 of the following year (1907) corn was planted in these 

 pots in order that any young larvae hatching from eggs in the earth 

 might find food ready for them. No search for larvae was made until 

 June 22, at which time Pot No. 1 was overhauled. The roots of the 

 corn plants were uninjured, and no root-worms were found. The next 

 examination was made July 12, when two corn plants in Pot No. 2 

 were seen to be burrowed by the corn root-worm, and a larva about 5 

 mm. long— that is, somewhat less than half grown — was found in one 

 of them. 



