Insects. 1461 



Note on the Aphis of the Hop or Hop-jiy. — At the end of last June I observed 

 that the leaves of the hops in the neighbourhood of Birch wood were much infested by 

 Aphides. One generation seemed to have lately passed away, and its successors were 

 larvaa of two sizes, the smaller being apparently the offspring of the larger. 'The 

 winged insect was comparatively scarce, and I did not see any pupae. The little lar- 

 vae are spindle-shaped, greenish white, half transparent, rather flat : their antennas 

 white, shorter than the body ; their eyes black : their mouth white ; their tubes white, 

 about one-fifth of the length of the body : their legs white, and moderately long. 

 When full-grown they are a little broader, and of a grass-green colour ; the tarsi, and 

 the tips of the antennae, of the mouth, of the tubes, and of the tibiae are black : some- 

 times the antennae are black ; the base white : sometimes the body is pale green, with 

 interrupted bands of darker green. When winged it is green : the disk of the head 

 and the disk of the mesothorax above and below are black : there are a few short black 

 bands across the disk of the abdomen, and a row of large dark spots on each side : the 

 antennae are black, a little longer than the body : the mouth is pale green ; its tips 

 black: the tubes are dull green; their tips black : the legs are pale yellow, moderately 

 long ; the tarsi and the tips of the thighs and of the tibiae are black : the wings are 

 limpid, much longer than the body ; the squamulae are pale yellow ; the stigma is pale 

 brown ; the nerves are brown. It is a small species. Many of the Aphides seemed 

 about to perish from famine in consequence of the withering of the leaves whereon 

 they were fixed, but the Coccinellse and Syrphi were numerous, and by devouring the 

 Aphides, adjusted in some degree their number to the quantity of their food. Aphides 

 are most abundant in hot seasons when vegetation is most vigorous, for then the 

 food of plants is provided in the greatest quantity, if moisture is not wanting. In 

 agriculture, it is said that as soon as we know what are the substances required by 

 crops, we shall at once know how to restore to the soil those substances which each 

 crop removes, and thus be enabled to obtain crops of the same plant for any number 

 of years in succession from the same soil. But a rotation of crops will have the effect 

 of diminishing the number of Aphides. The ravages of these creatures are restrained 

 by one species being generally unable to thrive on more than a few nearly allied kinds 

 of plants, though it often occurs elsewhere. 



" But brief the bloom, and vain the toil ; 

 It is not native to the soil." 

 Sometimes the young ones are born on a plant that yields them no nourishment. 



" Spem gregis, ah ! silice in nuda connixa reliquit," 

 By varying a crop every year, the young ones, when they appear in the spring, being 

 without the means of nourishment will soon die, and the plant will be comparatively 

 free from their ravages. For this purpose we must first ascertain what are the ele- 

 ments and substances of each plant on which Aphides feed, and what variation of this 

 composition renders the plant unfit for the digestion of the insect. The ground for 

 the hop plantation should be changed every year, the new site being as far removed 

 as possible from the old, and perhaps it will be found advantageous to have new poles 

 every year for the support of the hops, and the old poles may be burned in the winter. 

 Having announced my attention of publishing descriptions of the British Aphides 

 with reference to the injuries which they cause to agriculturists and gardeners, I take 

 this opportunity of requesting any information thereupon, — Francis Walker. 



