96 INDIRECT INJURIES CAUSED BY INSECTS. 



country both these plants suffer most are the Aphides, commonly called 

 leaf-lice, but which properly should be denominated plant-lice. As almost 

 every animal has its peculiar louse, so has almost every plant its peculiar 

 plant-louse; and, next to locusts, these are the greatest enemies of the 

 vegetable world, and, like them, are sometimes so numerous as to darken 

 the air. 1 The multiplication of these little creatures is infinite, and almost 

 incredible. Providence has endued them with privileges promoting fecun- 

 dity which no other insects possess : at one time of the year they are 

 viviparous, at another oviparous; and, what is most remarkable* and 

 without parallel, the sexual intercourse of one original pair serves for all 

 the generations which proceed from the female for a whole succeeding 

 year. Reaumur has proved that in five generations one Aphis may be the 

 progenitor of 5,904,900,000 descendants ; and it is supposed that in one 

 year there may be twenty generations. 2 This astonishing fecundity ex- 

 ceeds that of any known animal ; and we cannot wonder that a creature 

 so prolific should be proporticnably injurious : some species, however, seem 

 more so than others. Those that attack wheat, oats, and barley, of which 

 there are more kinds than one, seldom multiply so fast as to be very 

 noxious to those plants ; while those which attack pulse spread so rapidly, 

 and take such entire possession, that the crop is greatly injured, and some- 

 times destroyed by them. This was the case with respect to peas in the 

 year 1810, when the produce was not much more than the seed sown; 

 and many farmers turned their swine into their pea-fields, not thinking 

 them worth harvesting. The damage in this instance was caused solely 

 by the Aphis, and was universal throughout the kingdom, so that a suffi- 

 cient supply for the navy could not be obtained. The earlier peas are 

 sown the better chance they stand of escaping, at least in part, the effects 

 of this vegetable Phthiriasis. Beans are also often great sufferers from 

 another species of plant-louse, in some districts, from its black colour, 

 called the Collier, in others the Dolphin, which begins at the top of the 

 plant, and so keeps multiplying downwards. The best remedy in this case, 

 which also tends to set the beans well, and improves both their quality 

 and quantity, is to top them as soon as the Aphides begin to appear, and 

 carrying away the tops to burn or bury them. In a late stage of growth 

 great havoc is often made in peas by the grub of a small beetle (bruckus 

 granarius), which will sometimes lay an egg in every pea of a pod, and thus 

 destroy it. Something similar, I have been told (I suspect it is a short- 

 snouted weevil), occasionally injures beans. In this country, however, 

 the mischief caused by the Bruchus is seldom very serious; but in North 

 America another species (B. pisi), which is also found here, but not to 

 any very injurious extent, is most alarmingly destructive, its ravages 

 having been at one time so universal as to put an end in some places to 

 the cultivation of that favourite pulse. No wonder, then, that Kalm should 

 have been thrown into such a trepidation upon discovering some of these 

 pestilent insects just disclosed in a parcel of peas he had brought from 

 that country, lest fie should be the instrument of introducing so fatal an 

 evil into his beloved Sweden. 3 In the year 1780 an alarm was spread in 



1 I say this upon the authority of Mr. Wolnough of Hollesley (late of Boyton) in 

 Suffolk, an intelligent agriculturist, and a most acute and accurate observer of 

 nature. 



2 Keaum. vi. 566. * Kalm's Travels, i. 173. 



