No. 104.] 119 



Although generally known as a spider, it is a trae mite. In classi- 

 fication it stands next to the spiders, and at the head of the mites, 

 in the family of the Trombididce, which contains the most highly 

 organized species of the Acarina. A distinction available in separat- 

 ing the mites from the spiders is that the former are without a 

 pedunculated abdomen. The abdomen instead of being joined to a 

 thorax by a narrow joint of attachment is united to the last of the 

 leg-bearing segments without any well-defined groove of separation. 



The webs which this species and its associates spin upon the under 

 side of leaves and adhering closely to them, are of an extremely 

 fine and delicate texture. A careless observer would not suspect their 

 true character, but would pass them by as a simple sheen upon the 

 leaf. The separate threads are so fine that they are not to be seen even 

 by the aid of a magnifying glass, but are only visible when combined 

 in an extended web. The silk is secreted from a minute nipple under- 

 neath the end of the abdomen. Beneath the web may often be 

 found a large colony of the mites, embracing both old and young, 

 in different stages of maturity, where, under this safe shelter, they 

 are actively engaged in feeding upon the leaf. After biting with the 

 mandibles with which they are provided through the surface of the 

 leaf, they insert the sucking apparatus and imbibe the juices. Small as 

 is each individual wound, the aggregation of the myriads soon tells 

 upon the leaf and plant, which discolors, droops, turns yellow and 

 perhaps dies under tlie attack. 



It is unfortunate that this insect is so general in its food, for 

 scarcely any tender garden plant is free from liability to its attack. 

 In addition to the Calla, Spircea, violet, and Thunbergia above 

 named, it was also present upon the leaves of Ilitella, Tropceolum^ 

 Adlumia, and beans, sent with the inquiry. Their examination by 

 Prof. Herbert Osborn, to whom they were submitted, showed the 

 presence upon each of the same insect, in the egg, larval and perfect 

 stages. 



This little mite, under favoring conditions, may multiply to an 

 incredible extent, and become very injurious. A notable instance 

 of this has lately been brought to my notice. Leaves of a quince 

 tree infested by this species were sent to me for name, under date of 

 August 11th, by Prof. Arthur of the New York Experiment Sta- 

 tion, at Geneva. He reports the attack as occurring in one of the 

 largest qumce orchards in the State, about four miles from Geneva. 

 The leaves upon many of the trees were like those received by me, 

 which were nearly destroyed. The attack was rapidly spreading 

 tliroughout the orchard, and the fruit upon the most seriously in- 

 fested trees would be an entire loss. 



Prof. Arthur was experimenting with the kerosene emulsion to 

 kill the insect, but with what success has not been learned. Properly 

 applied, it could not fail of accomplishing the purpose. A favorite 

 remedy, long used in green-houses, has been syringing with a soap 

 solution in which sulphur is mixed. Quassia has also been thought 

 serviceable when added to the mixture. It is quite important 



