SOCIETY OF CENTRAL ILLINOIS. 263 



with most insects, but are large as compared with other phmt mites. 

 They may be red in coh>r, l)ut quite as ofteu are pale whitish yellow 

 and may be variously marked with black. Several species of the 

 genus to which they belong may occur in this country, but probably 

 most of those which have been noticed as destructive belong to the 

 one species, Tcfranijchus telariiis. They live exposed on the leaves 

 and stems of plants, occurring usually in greatest numbers on the 

 under side of the leaves and spinning there a slight webbing of 

 silken threads. The injury they do consists in puncturing the leaves 

 a))d withdrawing the sap. Where numerous the plants soon become 

 weakened, the foliage becomes yellow, and if they are not attended 

 to will die. The leafage is occasionally literally covered with the 

 mites and their eggs, together with their cast skins. 



Where these pests occur in hot houses or in small beds of 

 plants, perhaps even on shrubbery, they can be checked ])y repeated 

 and generous drenching of the plants with water. They thrive best 

 during dry seasons, and it is only then that their depredations be- 

 come serious. Moisture, on the other hand, is for some reason ob- 

 noxious to them, and we have fortunately in it a simple and effective 

 remedy for their injuries. The application of water to trees out of 

 doors in sufficient quantities to destroy the mites is not, however, so 

 simple. Applications of dilute kerosene emulsion will here answer 

 the same purpose. 



In the summer of 1880, after a season of drouth, the arbor vitae 

 trees in Central Illinois were many of them left in an unhealthy 

 condition. The leaves were of a decided vellow cast, and so little 

 vitality seemed left in many of them that it was feared they would be 

 lost. An examination of such trees showed not one of the usual 

 traces of insect injury, but upon the lower leaves and near the 

 trunk, upon the ])ranches, were many cast skins and occasional eggs, 

 which proved to be the remains of colonies of red spiders which had 

 damaged the trees earlier in the season during the dry period. The 

 following year the trees regained their usual thrifty appearance, and 

 it was not until 1884 that an opportunity occurred for trying reme- 

 dial measures upon them. During the summer of that year the red 

 spider appeared in such numbers as to seriously injure both arbor 

 vita' and larch. The latter tree was soon rendered brown, ami some 

 of those examined were alive with the mites. It was found on trial 

 that two applications of a dilution of kerosene emulsion, containing 

 two and a lialf \)or cent, of kerosene, though ap|)lied with imperfect 

 apparatus, helped the trees at once, a fact which was soon apparent 

 in the freshened appearance of the trees as compared with those not 

 treated. We can recommend kerosene emulsion for out of door ap- 

 plications with a good deal of confidence. For in-door application 

 also we would recommend it where the need of immediately check- 

 ing injury to the plants is of moment. Powdered pyrethram seems 

 to have little effect. Plants embrowned with it perish before one's 

 eyes. 



