The Red Spider (Spinning Mite). Tetranychus, telarius.

This is a species of the order Acarina, or mites, in which are included many familiar and unpleasant creatures, as ticks, cheese mites, itch mites, among others. A familiar but disagreeable acquaintance of country people-the harvest bug, Tetranychus autumnalis-is another species of the genus of spinning mites.

Gardeners know the red spider, as it is commonly called, which is found on the under leaves of many plants both in the open air and in greenhouses and frames, and make lamentations over the great mischief it causes. It is not a spider, being essentially different in form, as will be seen by the above figure, though it spins a kind of web upon the under surfaces of the leaves of the plants it infests, for its protection, and it has a peculiar arrange- page 29 ment of stiff hairs with round terminations, as shown above, for the purpose of spreading and fixing this web. Nor is it always red. Its colour is also sometimes green, sometimes brown or brick red, varying, as some naturalists think, according to its food. Upon hop leaves it has been found of many shades of colour, ranging from green, with tiny black specks on the sides of the mite, all through the variations between brown and bright red, upon the same leaf, rather indicating that the differences in colour are hardly attributable to diet, but to degrees of age. It is difficult to detect the presence of red spiders even when they are bright red, and almost impossible to see them when green or brown without a glass, so that casual observers or persons in any degree shortsighted do not discover them upon hop plants until considerable injury has been done.

Indeed for some time the work of these mites upon hop plants was mistaken for the effect of drought and heat, particularly as the injury was first noticed upon badly drained spots, where drought would naturally show its results. This supposed disorder was called Fireblast, because the leaves turn bronze-coloured at first, then they become yellowish red, as if they had been burnt. In Germany the hop planters term it Kupfer-Brand. As red spider is only troublesome to hop plants in hot, dry seasons, it is easy to understand that its action may be mistaken for that of heat and drought.

Many would think it impossible that this tiny mite could work much harm upon the masses of vegetation in hop plantations. In 1868, when the summer was excessively hot and almost without rain, the crop was utterly ruined by red spiders, upon thousands of acres in England and upon the Continent In Tasmania it is frequently very troublesome, so that the planters irrigate the hop land to destroy it in the ground before it can get to the plants. There was a sharp attack in England also in certain localities in 1872. During the late cycle of wet summers there was no sign of red spider. In 1884 there were clear indications of an attack in parts of Kent, Worcestershire, and Herefordshire. The weather changed, however, becoming damp and cool, and the mites could not work.^*

In 1868, at the beginning of July, the lower leaves of the hop plants became discoloured, "fireblasted," as the labourers said. This discoloration rapidly spread upwards, extending even to the lateral shoots. After a time the leaves fell off, the plants being quite exhausted of sap, and it was impossible for them in most cases to form any hop cones. Where these were formed they quickly shrivelled up and dropped off. Upon close examination of the leaves they were found to be desiccated. Their juices had page 30 been sucked out by myriads of mites, whose fine webs covered their under surfaces with countless filaments. Many plantations which in June were green and flourishing looked at the end of July as if a scorching fire had passed over them.

Not only do the mites exhaust the juices of the plants by means of the barbed suckers with which their mouths are fitted, but they hinder their respiration with their webs and excrements.