90 THE APHIS VASTATOR ON OTHER PLANTS. 



sively affected by the vastator ; leaf after leaf dies, until 

 the plant becomes a mere withered mass. 



(370.) The marigold and several species of thistle are 

 also attacked by the vastator, and perish in the usual way. 



(371.) The peach and nectarine leaves are infested by 

 this parasite : it generally kills the leaves partially. 



(372.) The celery plant is commonly attacked to a small 

 extent by the vastator : I have never myself seen the 

 insect, however, upon this plant in sufficient quantity to do 

 more than kill a leaf. There are complaints about this 

 esculent, but I know not whether the injury complained of 

 is referable to this cause. The plant is more likely to 

 suffer when running to seed, than in its first year's growth. 



(373.) Such is an enumeration of the plants which I 

 have found to be affected with this parasite. And there is 

 no doubt that this list might be very much extended, as t 

 myself am adding to the number every day, and within 

 the last two or three days I have even discovered it abun- 

 dantly on the Convolvulus battata, or sweet potatoe. In 

 this examination I have observed that cultivated plants, in 

 which particular parts of the plant are excessively deve- 

 loped or hypertrophied, are more prone to injury than the 

 wild plants of the same species. In the wild plants the 

 injury generally spreads from leaf to leaf, whilst in the 

 cultivated varieties it appears to attack root and leaf at the 

 same time. 



(374.) The above list shows how fearful an attachment 

 this insect has to plants which are serviceable to man for 

 food, as well as for medicine, well entitling it to the name 

 which I have given it the vastator, or " destroyer." 



