KooK IV. 



OF VERMIN. 



2266. The fly genus {Musea) presents many curious species. The common flesh-fly {M. vomitona) {fig. 410.a) 

 deposits its eggs on the meat in our shambles and larders. These eggs (jb) speedily become larvse (r), are soon 

 full grown [d), change to the chrysalis state {e), and in 410 



a month the fly appears (a). The rapid multiplication 

 of the fly is thus calculated by Leuwenhoeck. " Let us 

 suppose, that in the beginning of June there shall be 

 two flies, a male and a female, and the female shall lay 

 144 eggs, which eggs, in the beginning of July, shall be 

 chafiged into flies, one half males and the other half 

 females, each of which females shall lay the like num. 

 ber of eggs ; the number of flies will amount to 10,000 : 

 and, supposing the generation of them to proceed in 

 like manner another month, their number will than be 

 more than 700,000, aU produced from one couple of flies 

 in the space of three m.onths." The Hessian fly {M.pu- 

 pilionis) (/) is very destructive to wheat and rye, and has 

 occasionally been a source of great alarm to our agri- 

 culturist?. 'The cheese-fly {M-putris) (g), well known to 

 housewives under the name of hopper, deposits its eggs 

 in the crevices or holes of the cheese, whence those nu- 

 merous maggots (/i), that so much amuse us by their 

 agility and surprising leaps. One of these insects, not a 

 quarter of an inch in length, has been known to leap 

 out of a box six inches deep. The chrysalis (2) is 

 straight and crusty. 



2267. The gnat {Cttlex) is frequent in the neighbor- 

 hood of waters and marshy places. In southern re- 

 gions there is a larger species, which is known by the 

 name of musquito. Its bite is painful, raising a 

 considerable degree of inflammation, and its continual piping note is exceedingly irksome where it abounds, 

 especially during the night. When it settles to inflict the wound and draw the blood, it raises its hind 

 pair of feet. In Lapland, the injuries the inhabitants sustain Irom it are amply repaid by the vast num- 

 bers of water-fowl and wild-fowl which it attracts, as it forms the favorite food of their young. The 

 fecundity of the common gnat {C. pipiens) (fig. 410. k) is as remarkable as that of the flesh-fl_v. 



2268. The tabanus genus greatly resembles musca, and produces some species troublesome to men and 

 other animals on whose blood they feed. The spider fly (Ilippobosca) inhabits woods. The species known 

 as the forest-fly [H. equina) [fig. 410. /) is particularly tormenting to the horse. 



2269. The aptera, or insects without wings in both sexes, is composed of genera of such 

 varied forms, that no other general characters can be affixed. Linnaeus comprehended in 

 this order spiders, lice, lobsters, crabs, shrimps, &c. which Leach and most other modern 

 naturalists class separately. 



2270. The louse {Pediculus) and flea (Pulex) are well known : the only genera of this order which ai e trou- 

 blesome in gardens are the mite-spider {Acarus), the common spider (Aranea), and the woodlouse (Onivcvi.^ 



411 



2271. The red spider is the Acarus tellurius, L. (fig. 411. a), and 

 the same name is also applied by gardeners to the scarlet acarus 

 {A. holosericeus, L.) (6), the only two British species of the genus 

 which infest plants, and to which perhaps they do more injury 

 than all other insects put together. Watering over the leaves is 

 the well known preventive and remedy : the water should be 

 applied to both sides of the leaf in a finely divided state, and with 

 great force, so as to dash the insects to the ground. For this 

 purpose Read's syringe is the most eiKcient implement at present 

 in use. The sheep-tic {A. reduviiis) {c), the dog-tic {A. ricini/s) 

 (d), the cheese-mite [A. siro), and the itch-mite (mite de la gale, 

 Fr.) [A, exulcerans, L.) which inhabits the ulcers of the itch, are 

 the principal species mentioned by Linnseus ; but some naturalists 

 consider that every animal, and most plants, have their peculiar 

 species of acarus. The harvest bug is by some considered an 

 acarus, and by others a phalangium. 



2272. The common spider {Aranea) is a numerous genus, and 

 very prolific : as they live entirely on insects they cannot be con- 

 sidered as otherwise injurious in gardens than by their unsightly appearance. 



2273. The wood-louse {Oniscus) is of retired habits, shunning the light and the heat of the sun. It 

 lives on leaves, fruit, and also on animal substances, and car.ts its crust or skin like the spider. In 

 gardens it is easily caught by bundles of reeds or beans, or other hollow stalks, like the earwig. The 

 O. aquaticus {fl^. c) is common in springs and clear ponds, or cisterns of watei\ The dog-tic and water onis- 

 cus both re<fuire to be magnified to be studied properly (/, g). 



Ff 2 



