Page:The American Cyclopædia (1879) Volume I.djvu/619

 APENRADE APHIS 583 tertiary formations containing abundant fossils distinguish many of the offshoots, and, as has been already noticed, groups of purely volcanic mountains appear in many places among the Sal (-Apennines, and even approach the main range, to the system of which they in no way belong. This volcanic formation is found only on the western side of the chain. For the vegetation of the Apennines, the rivers flow- ing from their, sides, the methods of cultiva- tion employed on their fertile lower slopes, and the people inhabiting the mountain coun- try, see ABBUZZO, CALABRIA, and ITALY. APENRADE, a seaport town in the Prussian province of Schleswig, situated on the Baltic, 20 m. N. of Flensburg; pop. in 1871, 5,932. On March 30, 1848, there was here an en- counter between the Prussians under Wrangel and the Danes. Near the town is the castle of Brundlund. APHIS, the plant louse, or puceron, a genus of insects included in the order homoptera. The number of species is very large ; 326 are de- scribed in Francis Walker's list of specimens of homopterous insects in the collection of the British museum. Almost every sort of plant furnishes a living to a different kind of aphis. The attacks of these insects are often ruinous to certain crops. The A. rosce is most destructive to the rose tree, on which it is constantly found. Apple trees and pear trees are attacked by a species of aphis which injures their fruit. Cab- bage and turnip crops are sometimes destroyed by swarms of the A. brassicce. Their attacks on all plants seem to be regulated by the health of the plant and the peculiarities of the season. If atmospheric conditions render the plant un- healthy, then the aphia appears ; if these cease, the aphis disappears; and one crop of plants may be attacked several times in the same year. Most species of this insect are green ; but a dark species, the bean dolphin, or A. fabce, attacks the bean, whole acres of the plant being suddenly covered by these black insects. They have, however, many destructive foes: The larvae of the lady-bird (coccinellidce), the gyrphus or bee-like fly, the chrysopa or lace- wing, and several species of ichneumonidce, pursue and eat them very greedily. Tobacco is the principal remedy against destructive swarms of the aphis. In conservatories, or where plants can be placed under cover of any kind, they may be easily exposed to clouds of tobacco smoke, and that is the simplest way of destroy- ing the aphis ; but in the open air, where the fumes of tobacco easily disperse, the best way is to apply the tobacco in water. The affected parts may be syringed with the infusion of tobacco, and after the effect is produced, the plant may be washed by the rain or with pure water. These insects have a soft, roundish body, a small head, complete and half-globular eyes, antennae of from 6 to 11 joints, longer than the head and often hairy. The beak has its origin from the lower part of the head, be- tween the fore legs, and in the act of sucking is held nearly perpendicular. The wings, when developed, are 4 in number. The legs are very long and slight. Near the extremity of the abdomen above, most kinds of aphis are pro- vided with a pair of tubular horn-like process- es, through which they eject a sweet, thickish fluid, commonly called honey-dew, of which ants and many other insects are very fond. At the end of autumn many of the species, such as the A. quercus and the A. rosce, of both sexes, are numerous, some winged, and some without wings. While some can fly to a distance, others, without wings, are restricted to the neighbor- hood of their native plant. As soon as she has paired, the mother aphis deposits her eggs or larvae in a place fit for passing the winter, dif- ferent places being selected by different species. Some prefer the oak, and leave their eggs on some waving bough high in the air ; others in the crevices of the bark, or in a subterraneous receptacle. Bonnet supposes that the aphides are always viviparous, and never lay eggs; what are commonly called eggs, produced in the autumn, being a sort of cocoon, containing the young aphis enclosed in an envelope. This, however, is not universally admitted. The pa- rents die after disposing of their eggs or co- coons, and these remain torpid during the win- ter. All the aphides which appear in spring are females, which are endowed with a most wonderful spontaneous fecundity, no pairing being possible, as no males appear till autumn. Latreille states that one female during the sum- mer months will produce 25 daily, each of which will in turn do the same, and so on for several generations in a single season. Reaumur cal- culated that one aphis may be the progenitor of about 6,000,000,000 descendants in its own lifetime. The A. lanigera produces each year, says Prof. Owen in his "Lectures on Compara- tive Anatomy," 10 viviparous broods, and one which is oviparous ; and each generation aver- ages 100 individuals. The progression is 1, 100, 10,000, 1,000,000, 100,000,000, 10,000,000,000, 1,000,000,000,000, 100,000,000,000,000, 10,000,- 000,000,000,000, 1,000,000,000,000,000,000, for the 10 viviparous broods ; and by adding the oviparous generation, the result is 30 times greater. The female aphides thus produced are considered as larvae, presenting a more de- veloped condition than the larvae of coleoptera and lepidoptera. The compound eyes are com- pletely developed ; the antennae have attained their perfect shape and proportions, the 6 tho- racic legs their full size and power. The only subsequent change of these fertile larvae is an additional size and the manifestation of the or- gans of reproduction. In the last generation, which is the 7th, the 9th, or the llth, accord- ing to the species of aphis, the spontaneous power of reproducing their species is totally lost ; wings are developed, and winged male insects now make their appearance. The fe- males of the present generation are the winged insects which produce eggs and deposit them where they may be hatched by the sun in time?