PLANT BUGS, APHIDES, AND SCALE. 235 



maggot of the Ephedrus, so that not only is the young 

 aphis destroyed, but its destroyer also meets with its 

 retribution, for in turn it becomes the prey of Cera- 

 phron. The aphis is a parasite upon the wheat, the 

 Ephedrus a parasite on the aphis, and the Ceraphron 

 a parasite on the Ephedrus. Parasite destroys para- 

 site, and the wheat is freed. By such means the 

 otherwise overwhelming numbers 'of the plant-lice are 

 kept in check. ' 



Some of the most pernicious of insect pests are to 

 be found amongst this fraternity. Foremost of all in 

 the excitement and panic it has created is the Phyl- 

 loxera, which has attacked the vines on the Continent, 

 and even made its appearance in England. We have 

 long suffered in our hop-gardens from the devastations 

 of the Hop-fly. The white, woolly substance so 

 common on apple-trees, and known as " American 

 blight," is another of these insects. So, also, is a 

 similar appearance which may be observed on larch. 

 We are not deficient in the number of those which 

 cause direct injury, but can recognize none which 

 confer direct benefits, or at least any benefits which 

 we can appreciate. 



As an instance of the injurious effects of the " fly n 

 in hop-gardens, it has been stated that in the year 

 1802 the excise duty on hops, which in the previous 

 year was ^"100,000, fell to ,14,000, and that the 

 deterioration in value was entirely ascribed to the 

 ravages of the " fly." 



Passing from these minute insects, we have another 

 group known as Plant Bugs, of a much larger size, 

 but not capable of inflicting such widespread injury. 



