Elm. 291 



ELM. 

 INSECT ENEMIES. 



Canker-worm. See under APPLE. 



Elm Span-worm (Eugonia subsignaria, Hiibn.). Description. 

 These insects hatch from eggs as soon as the buds break in the 

 spring. The larvae are commonly known as measuring, or 

 span-worms. They are grayish-brown in color, having a large, 

 red head, and the last segment of the body is of the same 

 color. The larvae pupate about the end of June, and during 

 July and August the mature insect appears. It is a pure white 

 moth, the wings expanding nearly one and one-half inches. 



Treatment. When possible, the affected trees should be 

 thoroughly sprayed with Paris green used at the rate of one 

 pound to 150 gallons of water. This is the best remedy against 

 all insects which work on the foliage of shade trees, but when 

 the trees are large much difficulty is experienced in reaching 

 all parts. See also page 195. 



Gipsy Moth (Ocneria dispar, Linn.). Description. The 

 gipsy moth is found in America only in the immediate vicinity 

 of Boston. It has there caused great damage, as the larvae are 

 voracious feeders and take kindly to nearly all foliage. The 

 eggs of the moth are laid during July, August, and September, 

 generally near the pupa case of the female. They are deposited 

 in clusters, and covered with a thick layer of yellow hairs. The 

 following spring the young caterpillars appear, and for about 

 ten weeks they feed upon the foliage of most plants. When 

 grown they are two inches or more in length, and greenish- 

 brown in color. Each segment of the body bears upon either 

 side a tuft of hairs, while along the back there is a double row 

 of spots, those on the four anterior segments being purple in 

 color ; the remainder are brown. The insects pupate in some 

 sheltered spot on the trees, or in neighboring fences, etc. In 

 this state they remain about ten days, when the adults appear. 



Treatment. The caterpillars are readily destroyed by the 

 arsenites, Paris green and the arsenate of lead having been 

 most extensively used. The latter is effective when used at the 

 rate of two pounds to 150 gallons of water. It is not feasible 

 in many cases to make such applications, so the insects are 

 destroyed by collecting the eggs, and destroying them, and also 



