INSECTS INFESTING CROP. 61 



same time we must admit that their ravages are not, in 

 general, in proportion to their numbers, neither is there 

 any one that inflicts the same amount of injury on the 

 potato as the "fly" does, for instance, on the turnip, and 

 the aphis, or " black dolphin," on the bean crop. Curtis, in 

 treating of these numerous enemies, divides them into those 

 attacking the leaves and stems, and those attaching them- 

 selves to the tubers and roots. No sooner is the potato 

 "set" planted in the ground than it collects round it all the 

 wireworms in its vicinity, who at once take up their 

 quarters on it, and live upon it as long as it lasts. If they 

 injure the germ, the plant may never be able to push its head 

 above the soil, or may only produce a weak, sickly shoot, 

 owing to its stores of food being curtailed by their attacks. 

 At a later period of the growth of the plant, when tubers are 

 formed, these are frequently also punctured and injured by 

 the different wireworms. When the young plant has made 

 its appearance above the ground, various aphides, amongst 

 which may be noticed the Aphis rapce and the A. vastator, 

 make their appearance upon the haulm, where they re- 

 main as long as the stem and leaves remain green and suc- 

 culent. These insects puncture the leaves and live upon 

 their juices, and when they take possession of them in such 

 countless numbers as are seen in some seasons on the pea and 

 bean crops (p. 234, vol. i.), considerable injuries ensue. On 

 the potato, however, although they may nearly always be 

 met with, they seern to inflict little or no practical injury. 

 One noticeable feature in all the aphides is their enor- 

 mous powers of increase ; so that, where they are able to 

 inflict an injury, it may under certain conditions, from 

 their great numbers, be very serious. Curtis mentions, 1 

 as a proof of the great fecundity of these insects, that he 

 put three from the potato crop into a quill, and in six 

 hours they had produced forty-three young ones. For- 



1 Farm Insects, p. 429. 



