APHIS. 





bject of their choice, which, from the na- 

 ture of these insects, one would not, a 

 priori, expect ; yet I have seen the roots 

 of lettuces thickly beset with them, and 

 the whole crop rendered sickly and of lit- 

 tle value ; but such instances are rare. 

 They seldom attach themselves to the 

 bark of trees, like the aphis salicis, which, 

 being one of our largest species,and hence 

 possessing superior strength, is enabled to 

 penetrate a substance harder than the 

 leaves themselves. In the quality of the 

 excrement voided by these insects, there 

 is something wonderfully extraordinary. 

 Were a person accidentally to take up a 

 book, in which it was gravely asserted, 

 that in some countries there were certain 

 animals which voided liquid sugar, he 

 would lay it down, regarding it as a fabu- 

 lous tale, calculated to impose on the cre- 

 dulity of the ignorant ; and yet such is 

 laterally the truth. Mr. Curtis collected 

 some on a piece of writing-paper from a 

 brood of the aphis salicis, and found it to 

 be sweet as sugar; and observes, that, 

 were it not for the wasps, ants, flies, and 

 other insects, that devour it as quickly as 

 it is produced, it might, no doubt, be col- 

 lected in considerable quantities, and, by 

 the processes used with other saccharine 

 juices, might be converted into the choic- 

 est sugar or sugar-candy. The sweetness 

 of this excrementitious substance, the 

 glossy appearance it gave the leaves it fell 

 upon, and the swarm of insects this matter 

 attracts, led him to imagine that the ho- 

 ney-dew of plants was no other than this 

 secretion, which further observation has 

 since fully confirmed ; and not, as its name 

 implies, a sweet substance falling from the 

 atmosphere. On this opinion it is further 

 remarked, that it neither falls from the 

 atmosphere, nor issues from the plant it- 

 self, as is easily demonstrated. If it fell 

 from the atmosphc -re, it would cover every 

 thing it fell upon indiscriminately, where- 

 as we never find it but on certain living 

 plants and trees. We find it also on plants 

 in stoves and green-houses, covered with 

 glass. If it exuded from the plant, it would 

 appear on rail the leaves generally and 

 uniformly ; whereas its appearance is ex- 

 tremely irregular, not alike on any two 

 leaves of the same tree or plant, some 

 having none of it, and others being cover- 

 ed with it but partially. It is probable 

 that there never exists any honey-dew but 

 where there are aphides; though such 

 often pass unnoticed, being hidden on the 

 underside of the leaf: and wherever ho- 

 ney-dew is observable upon a leaf, aphides 

 will be found on the under side of the leaf 

 or leaves immediately above it, and under 



no other circumstance whatever. If by ac- 

 cident any thing should intervene between 

 the aphides and the leaf next beneath 

 them, there will be no honey-dew on that 

 leaf: and thus he conceives it is incontro- 

 vertibly proved, that aphides are the true 

 and only source of honey-dew. Of the 

 British species of aphides, one of the lar- 

 gest and most remarkable is the aphis sali- 

 cis, which is found on the different kinds 

 of willows. When bruised, these insects 

 stain the fingers with red. Towards the 

 end of September multitudes of the full- 

 grown insects of this species, both with 

 and without wings, desert the willows on 

 which they feed, and ramble over every 

 neighbouring object in such numbers, 

 that we can handle nothing in their vicini- 

 ty without crushing some of them, while 

 those in a younger or less advanced state 

 still remain in large masses upon the trees. 

 Aphis rosae is very frequent, during the 

 summer months, on the young shoots and 

 buds of roses : it is of a bright g'reen colour: 

 the males are furnished with large trans- 

 parent wings. A. vitis is most destructive 

 to vines; as A. ulmi is to the elm-tree. 

 Plate I. Entomology, fig. 3. 



It is found, that where the saccharine 

 substance has dropped from aphides for 

 a length of time, as from the aphis salicis 

 in particular, it gives to the surface of the 

 bark, foliage, &c. that sooty kind of ap- 

 pearance, which arises from the explosion 

 of gunpowder : it looks like, and is some- 

 times taken for, a kind of black mildew. 

 In most seasons the natural enemies of the 

 aphides are sufficient to keep them in 

 check, and to prevent them from doing 

 essential injury to plants in the open air : 

 but there are times, once perhaps in four, 

 five, or six years, in which they are mul- 

 tiplied to such an excess, that the usual 

 means of diminution fail in preventing 

 them from doing irreparable injury to 

 certain crops. 



To prevent the calamities which would 

 infallibly result from an accumulated 

 multiplication of the more prolific animals, 

 it has been ordained by the Author of 

 nature, that sucli should be diminished 

 by serving as food for others. On this 

 principle, most animals of this kind have 

 one or more natural enemies. The help- 

 less aphis, which is the scourge of the 

 vegetable kingdom, has to contend with 

 many : of these, the principal are, the 

 coccinella, the ichneumon aphidum, and 

 the musca aphidevora. The greatest de- 

 stroyer of the aphides is the coccinella, 

 or common lady-bird. During the winter 

 this insect secures itself under the bark of 



