Dec, 1916.] 



Notes on Ceutorhynchus marginatus. 



245 



of Ceutorhynchus, north of Mexico, which have been studied, forty- 

 seven according to Chittenden, have been found on cruciferous 

 plants. Blatchley and Leng (1916) state that C. ncgJcctns probably 

 feeds on Polygonum sp. The species of Ceutorhynchus occurring in 

 Europe have been found on many plants other than the cruciferse; 

 Polygonum is mentioned by Blatchley and Leng, and Bargagli (1883) 

 gives a long list of plants on which they occur. 



This beetle is evidently capable of playing an important part in 

 checking the spread of the dandelion. The writer has observed that 

 an enormous amount of seed is destroyed by the larvae of this beetle. 

 When four or five larva; are present a large percentage of the seeds 

 are destroyed. During the egg-laying period one thousand four 

 hundred dandelion heads were examined to determine the percentage 

 of infestation. These were gathered from five different localities 

 about Ithaca, N. Y., and are representative. Sixty-five per cent, of 

 the dandelions were found to be infested. The preceding summer no 

 counts were made but the writer is of the opinion that the infestation 

 was even greater. The following table gives the counts made in 1916. 



A number of counts was also made to determine the percentage 

 of seeds eaten in a single flower head. 



