356 APHIDES. 



resting, seemingly an immense migrating body : but, 

 slightly formed as they are, few creatures seem less 

 calculated for a distant removal ; and from whence 

 do they come ? Only two plants are in any way 

 remarkably infected with this insect ; and it seems 

 singular that these two, so different in their cha- 

 racters and nature, should commonly be equally 

 sufferers at the same time, which I believe they 

 are the bean-plant and the hop ; the former we 

 do not cultivate to an extent sufficient to give being 

 to such numbers, and the hop-grounds of Worcester 

 and Hereford are too distant (having an adverse 

 wind) to inundate us with these moving myriads. 

 It is more probable that the late rains have given 

 such a vigour to the bean-plant as to render its 

 circulating juices unpalatable to the creatures 

 abounding on them; and hence I conjecture they 

 have left the districts where this legumen is exten- 

 sively cultivated in Somersetshire, and journeyed 

 from a distance of, perhaps^ fifteen miles, with the 

 wind, in search of more suitable provender. But 

 the appearance and generation of insects, and this 

 race in particular, are involved in much mystery : 

 plants growing in houses^ removed from all con- 

 nexion with those that are infected, will yet regu- 

 larly produce them the cinerarias universally, and 

 one species, c. cruenta, most remarkably so. This 

 is a plant whose herbage annually dies down to the 

 root, and hence has no vegetation remaining to 

 conceal eggs, if there were any ; for these creatures 

 bring forth their young alive, in all the cases in 



