72 PROCEEDINGS ENTOMOLOGICAL SOCIETY 



-Mr. A. C. Morgan recorded an observation upon the toxic 

 effect of the food of the host upon its parasites. He said: 



"Upon undertaking the investigation of insects affecting to- 

 bacco in Tennessee in 1907 I expected to find that Apan teles 

 congregatus Say exercised a very appreciable control of the 

 tobacco horn- worms Phlegethontius, scxta Joh. and P. (/nin- 

 quemaculata Haw. Exactly the contrary was found to be the 

 case in so far as control upon tobacco was concerned. Almost 

 daily observations were made in the field during the latter 

 half of July, 1907, and during August and September, with 

 the result that only two parasitized larva: of Phlegethontius 

 were collected from tobacco. In one field of tobacco a row of 

 tomatoes had been planted in the place of a row of tobacco. 

 A count of the tobacco worms upon this row gave 67 parasit- 

 ized and 37 unparasitized. More than 200 lame were ob- 

 served upon the nearby hills of tobacco and not a single one 

 was parasitized by Apantcles. 



Observations during the seasons of 1908 and 1909 gave the 

 same resnlts as obtained in 1907. Wherever Phlegethontius 

 larva: were found upon tomatoes or upon wild solanaceous 

 plants a considerable parasitism by Apantcles always occurred. 

 In 1908 not more than 10 Phlegethontius larvae were found 

 upon tobacco parasitized by Apanteles, although more than 

 5,000 were collected and more than as many more came under 

 the observation of the collectors. The percentage of parasit- 

 ism upon tobacco was practically the same in 1909. Only occa- 

 sional parasitized .specimens were found. 



Further, it is entirely possible and more than probable that 

 the few Phlegethontius larvas that were found parasitized 

 upon tobacco had crawled upon the tobacco after being para- 

 sitized upon the wild solanaceous plants that were growing 

 in and around the fields. In 1909 several tobacco worms were 

 found parasitized upon Physalis sp. growing within a foot of 

 tobacco plants and not a single parasitized individual could be 

 found upon the tobacco. 



In the absence of more conclusive proof I have tentatively 

 assigned the reason for the lack of the parasitism of Phlege- 

 thontius larvae by Apanteles, when feeding upon tobacco, to 

 the toxic effect of the nicotine contained in the tobacco. 



-Mr. Hunter outlined the work being done on the insects 

 affecting cactus, commenting on the fact that insects which 

 were once regarded as beneficial by destroying the cactus plants 



