May, 1914.] Egg-Laying of the Rice Weevil. 321 



EGG-LAYING OF THE RICE WEEVIL, CALANDRA 



ORYZAE LINN. 



Frank H. Lathrop. 



The Rice Weevil, Calandra oryzce Linn., is well known through- 

 out the United vStates as a stored grain pest. It is especiall}^ de- 

 structive in the South, however, where it is known chiefly because 

 of its injury to corn (1, 4). In fact, it is often locally called 

 the Com Weevil. 



While studying the pest, the writer was impressed by its high- 

 ly adaptive method of oviposition, and the belief that a study 

 of the habit would be interesting and of some economic impor- 

 tance led to the observations included in this paper. 



The work was performed at Clemson College, South Carolina, 

 during the winter of 1912-1913, under the direction of Professor 

 A. F. Conradi, State Entomologist, to whom the writer is indebted 

 for valuable suggestions and assistance. The cuts are used through 

 courtesy of the South Carolina Experiment Station. 



WHERE THE EGGS ARE DEPOSITED. 



Each egg is deposited singly in a cavity previously dug in the 

 grain by the female beetle. Preparatory to oviposition, the 

 weevil moves over the surface of the com several times, examining 

 it thoroughly by means of the tip of the proboscis and the antennfe 

 before a suitable place is decided upon. When the place has finally 

 been chosen, the excavation of the cavity is immediately begun by 

 gnawing the material with the mandibles. Unless disturbed, the 

 weevil will usually finish the cavity when once started, but its 

 completion is by no means certain, for the weevil often becomes 

 apparently dissatisfied with the location even after the cavity is 

 well started, and a new location is sought. 



The place selected is usually near the edge of the corn, and, 

 when in position to excavate, the weevil is almost invariably 

 straddling the edge of the kernel. Nearly all of the eggs observed 

 were deposited in the soft starch or in the germ. Only rarely 

 was one placed in the homy starch, while a favorite location was 

 at the junction of the germ with the soft starch, and also at the 

 junction of the soft starch with the homy starch. 



In order to facilitate observation, the weevils were provided 

 with grains of corn that had previously l3een cut in two longi- 

 tudinally. The eggs were deposited on the broken siirfaces of 

 these half -grains, except in a few cases where they were deposited 

 in the germ at the point where it had been attached to the cob. 

 The outer, homy surface of dry com is apparently too hard for 

 the weevils to penetrate, for no eggs were observed in this region, 

 and, even when only whole grains were provided, the eggs were 

 deposited either in the gcmi or in the soft .starch at the outer end 

 of the kernel. 



