190 JOURNAL OF ECONOMIC ENTOMOLOGY [Vol. 12 



wheat, and, in fact, any place where there is protection. It is not unus- 

 ual to find them in large number under piles of Russian thistle that have 

 collected along a fence. They also probably make use of the burrows 

 of the various insects, and animals common to their locality. Snow 

 (1877, p. 19) found twenty adults under bones near Colorado Springs, 

 Colorado. 



The adults apparently have a wide range of food habits. In the 

 field they have been found feeding on evening primrose, Russian thistle, 

 and alfalfa. In the rearing cages they fed sparingly on smart weed and 

 on wheat leaves, while they showed a great preference for heads of 

 wheat, soaked wheat and bran. Examinations made in the field indi- 

 cate that they may feed on the wheat in the stack and shock, especially 

 if it becomes damp. When confined on a small plot of young wheat 

 they destroyed it in a few days. In one case a beetle was found feeding 

 on a nymph of Melanoplus differentialis, but it was impossible to deter- 

 mine whether it had killed the grasshopper or not. It is not unusual 

 for them to feed on the dead or weakened members of their own kind. 



Length of Life-Cycle 



Three generations of this insect have now been reared from adults 

 collected in the field in 1915. Each generation has occupied about one 

 year and the data secured in this study coincides very closely with the 

 field observations. Taking the average length of the various stages, 

 each brood required 341 days from the time the eggs were laid until the 

 adults emerged. The essential data showing the length of the life- 

 cycle are summarized in the following table: 



Summary of the Length of the Life-Cycle 



Stage Minimum Days Maximum Days Average Days 



Egg 6 19 9.7 



Larva 292 355 317.7 



Pupa 8 25 14.1 



Life-cycle 306 399 341.5 



Enemies and Parasites 



Very few natural enemies are known to attack Eleodes opaca. 

 Bruner (1892, p. 12) records finding the eggs of a tachinid on the elytra. 

 Each year that these studies have been carried on a few beetles have 

 been collected in the field from which have been reared specimens of 

 the hymenopterous parasite, Perilitus eleodis Viereck. In no case has 

 the percentage of parasitism been high, and the relation of this para- 

 site to opaca has been given but little attention. From the notes at 

 hand, the behavior appears to be the same as in the case of Eleodes 



