THE DESEET CORJSr FLEA-BEETLE. 



11 



''feeding mines/' while in others the feeding may produce a groove 

 along one side of the root, the larva finally entering the root and the 

 tunnel being continued within the same. Often where two tmineis 

 pass, the root is entirely cut off, and as is the case with small fibrous 

 roots, they are often entirely consumed. This feeding habit fre- 

 quently makes it quite difficult to locate any larvse except those that 

 were completely matured, and hence they were usually found in the 

 soil at some distance from the root. The larvse consume a consid- 

 erable amomit of food. A single larva confuied in a plaster of Paris 

 cage entirely consumed a section of root one-fourth of an inch long 

 and one-sixteenth of an inch in diameter. 



LARVAL FOOD PLANTS. 



The food plants of the larvas do not differ materially from those 

 of the adults. The amount of damage done to these various food 

 plants does, however, differ con- 

 siderablj" as between the larva and 

 adult. AKalfa is rarely, if ever, 

 injured by the adults, while the 

 larvae do a considerable amount of 

 damage to alfaKa roots, especially in 

 alfalfa fields which have been seeded 

 to a gram crop such as barley, oats, 

 or wheat during the winter. It is 

 upon corn, however, that the larvae 

 do their greatest damage. This is, 

 of course, due to the fact that tlie 

 feeding of the adults is concentrat- 

 ed upon newly gi-owing corn each 

 spring, and egg deposition conse- 

 quently becomes much heavier, the resulting damage being accord- 

 ingly great. 



THE PREPliPA AND PUPA. 



When the larv^a bocomc^s full grown it constructs an o])l()ng earthen 

 cell in which to change, (1) to a transitional or prepupal stage, and 

 (2) after a further pericjd of a few days, to the true pupal stage. 

 These pupal cells average about three-thirty-soconds of an inch in 

 length, the inner walls being quite smooth. In constructing its cells 

 the larva, owing to the fact that it is longer than its cell, must be 

 doubhid back upon its(Qf, thus working in very close quarters. As 

 soon us th(! cell is complettid tin; larva cliauges to a prepupa. In this 

 stage the body length shrinks while the diameter greatly increases, 

 and th(^ larva changes to a plump, i-otund object shaped like a ques- 

 tion murk. This stages, us shown })y Tuble: IV, varies in length 

 from 2 to 8 days, th(5 average })eiiig y,A days for 10 specimens. This 



Fig. 6.— Section of corn root showing injury 

 by larvse of the desert corn flea-beetle. 

 About one-half natural size. (Original.) 



