Spider, or Aranea, L. a genus of insects comprehending 50 species, of which the following are the principal; namely:
1 The Common House-Spider, is generally of a black-colour; has eight legs, each of which is furnished with three joints, and terminates in three crooked claws. This insect has eight eyes; and, in the fore-part of the head, there is a pair of pincers, or claws, with which it kills flies, etc. for food. It is also provided with five warts or prominences, at the extremity of the abdomen, through which its viscous filaments are evolved.
Spiders abound in almost every house, spinning their webs in corners of the ceiling, where they are not disturbed. The females are very prolific, laying from 4, to 500 extremely minute eggs ; and, tho' both sexes mutually devour each other with great ferocity, except in the breeding season, their numbers are not perceptibly diminished.
These insects are remarkable for their industry: their appearance, however, excites a degree of disgust in many weak-minded persons, who are apt to persecute and destroy them, without mercy. But, independently of their utility in reducing the number of flies that appear during the summer, they afford a very accurate natural barometer ; because the celerity, or indolence, with which they work, indicate the approaching variations of the atmosphere. Thus, if the weather be about to change, and become wet, or windy, the sagacious creatures make the terminating filaments that support their web, uncommonly short. But such threads be extended to an unusual length, the weather main serene for tea or twelve days or for a longer period, according to the proportionate extension of the former. On the contrary, when the spides are totally inactive, rain will shortly follow ; but, If they continue to spin during a shower, it is a certain indication, that the rain will speedily cease, and be succeeded by calm, fair weather.
2. The Calycina, or Garden Spider, varies from the preceding species only in its having a round, pale-yellow belly, and two hollow points. It inhabits the or cups o flowers, after the floral leaves are decayed: where it preys upon bees, and other flies, that resort thither for honey. - This insect yields a kind of silk, which is by some deemed little inferior to that produced by the worm ; but, as the filaments of the former are, in the opinion of Reaumur, not equal to those of the latter, either in strength or lustre, they are never employed in manufactures.
Spider, the Red, or Scarlet Tree-mite, Acarus baccarum, L. a small insect, having a roundish body, and a smooth, glossy skin colour is a deep-red, and the whole animal appears to be distended, and ready to burst. It frequents currant and other fruit-trees ; but is particularly destructive in hot-houses. Hence gar-deners have resorted to different methods of extirpating them, and especially that of sprinkling them with a strong ley of wood but, as the saline particles of this liquor are very hurtful to tender plants, it will be more advisable to remove such vermin, by means of a common painter's, brush; - their depredations may likewise be prevented; by keeping the hot-house perfectly clean. - See also the arti-cles vol. iii p. 19, and Pink apple, vol. iii. p. 3
Spider, the Red. - Independently of the method of exterminating these vermin, already suggested, the following is recommended by Mr. Forsyth. It merely consists in irrigating the infested plants with lime-water, in the afternoon, particularly on the lower side of the leaves. In hot-houses, however, he advises a barrow -engine to be filled with soft water, and all the plants to be sprinkled, by directing the stream against the top-lights, and shelves, till the water be an inch deep in the paths. But, where the building will not admit of the entrance of a barrow-engine, the front or top-lights must be slidden down, and the water poured in, from above. When this affusion is commenced, if in the, inside, every light ought to be shut; but, if the fluid be introduced from without, one light only should be opened at a time; and which must be shut, as soon as the part opposite to it is sufficiently watered. The other lights are then to be successively removed ; and, when the irrigation is completed, the house should be carefully closed till the next morning. In consequence of this operation, vapours will arise in every part of the building; cover all the plants; and effectually destroy the red spider, together with all other vermin. Mr. F. farther observes, that the watering must be repeated every day, during hot weather; and that it will, in general, shorten the labour, which would otherwise be required in irrigating plants. Such vegetables, however, as require obpious humidity, ought to be watered previously to sprinkling the house : thus, the plants will imbibe all the moisture, and the paths will become perfectly dry, during the night.