26 DEPARTMENT BULLETIN 1267, U. S. DEPT. OF AGRICULTURE 



DUKATION OF THE ADULT STAGE 



The writers have stated that the adults of the overwintering gen- 

 eration of Euetheola rugiceps perish, under natural conditions, by 

 midsummer. In the experimental cages numerous beetles of this 

 generation not only survived the summer but in some instances lived 

 until late in the fall. This late survival possibly was due to the pro- 

 tection which the beetles received from the extremes of heat and dry- 

 ness to which in nature they are exposed. A heavy mortality among 

 the beetles immediately after the mating season is evidenced not only 

 by the large numbers of dead beetles found in the field at that time 

 but also by the fact that corn planted late in the season — after June 

 1 — is almost invariably much less severely damaged than that planted 

 earlier. The longevity of adults in the breeding cages was undoubt- 

 edly due to the better care they received, as other adults, confined 

 in similar cages but left exposed in the open to as nearly natural con- 

 ditions as possible, perished in midsummer within a few weeks after 

 the cages were started. 



This view is supported by the testimony of others who have had 

 experience with this species. Howard (7) mentions a correspondent 

 at Canton, Miss., who reported that previous to July 9 he had had 

 little difficulty in finding the adults, but after a week of dry weather 

 they had entirely disappeared. Sherman (11) also quotes a corre- 

 spondent who, writing on June 14, reported that, although the beetles 

 had been very numerous and destructive in his cornfields, he had 

 noticed that within the last few days the dead beetles could be seen all 

 about the field. He added that his corn crop had been so completely 

 destroyed that the field was plowed up on June 1 and a new crop 

 planted a week later but that this second crop remained uninjured. 



Apparently the duration of the adult stage in the latitude of Vir- 

 ginia is from 9 to 11 months. The results obtained in experiments in- 

 dicate that under exceptional conditions in nature the adult stage 

 may conceivably last from a year to 14 months. 



SPECIES LIKELY TO BE MISTAKEN FOR EUETHEOLA RUGICEPS 



Euetheola rugiceps is often associated with other species of scara- 

 baeid beetles which may be easily confused with it. Its most constant 

 associates are its close allies, Ligyrus gibbosus (De Geer) and 

 Dyscinetus trachypygus (Burm.). For this reason these two species 

 will be considered in somewhat greater detail than the remaining 

 forms. 



LIGYRUS GIBBOSUS (De Geer) 



The life history of Ligyrus gibbosus is essentially the same as that 

 of Euetheola, rugiceps. The larvae of L. gibbosus develop more 

 rapidly, consequently the adults of the new generation appear earlier 

 in the fall than those of Euetheola rugiceps. The writers have never 

 found L. gibbosus injuring corn in the field, nor could it be induced 

 to feed upon corn in breeding cages. 



In general form, size, and coloration the larva of L. gibbosus^ re- 

 sembles that of E. rugiceps. As in the latter the fully chitinized 



