232 FIFTH REPORT OF THE ENTOMOLOGICAL COMMISSION. 



truuk are almost equally eflBcacious. Care and attention, and, above all, 

 CO operation among those suffering from these worms, will enable us to 

 check their ravages. 



14, Thk ei.m span-worm. 



Eugonia suhsignaria (Hiibuei). 



Order Lepidopteka ; Family Piial.exid.e. 



Hatching from the eggs as soon as the leaves unfold and living unobserved for a 

 week or two on young shoots in the tree tops, measuring or span worms, resembling 

 the twigs of the elm in color, with a large red head, and the terminal ring of the body 

 bright red ; pupating towards the end of June, and during July and August trans- 

 forming into a snow-white moth. 



This insect is widely spread. I have 

 observed it in the forests of northern 

 Maine in August, and it is common in 

 the Middle States. It is very destruc- 

 tive to the elms in New York City, 

 Brooklyn, and Philadelphia, though not 

 known to be destructive in the country. 

 The moth may at once be recognized bj^ 

 the snow-white body and wings, the an- 

 terior pair being angular and the hinder 

 pair slightly notched. It is, according 

 to Fitch, still more destructive to the 

 linden than to the elm. 



From a pamphlet by H. A. Graer and 

 Edw. Wiebe, entitled "The measure- 

 worm, a description of the insect, in all 

 its metamorphoses, etc." (Brooklyn, 1862), we quote the following facts: 

 The eggs are deposited by the female moth toward the beginning of July, not only 

 on trunks and branches of early-leaving trees, but also on numerous other objects, to 

 the number of from 20 to 250, in irregular clusters. During this period they are about 

 the size of a small pin's head, conical in form, and somewhat compressed at their 

 points; first of a yellowish, then of a light olive green, and later of a dark brown. 

 They are covered with a thick, sticky glutinous matter and adhere strongly to the 

 object on which they are deposited. They are usually found on the under side of 

 branches, and almost always below the connecting points of the same, apparently for 

 their better protection and with the design of opening several avenues for the young 

 brood to find subsistence. The number of eggs generally decreases from the base of 

 the branches towards their extremities. 



In this state the eggs remain unaffected by rain or frost, seemingly unchanged, 

 until the time when our shade trees unfold their first leaflets, which (subject to the 

 weather) is usually between the 15th of April and the 15th of May. 



Little caterpillars then creep from these eggs, eagerly enjoying the rays of the 

 sun on warm days, and carefully hiding themselves under the young foliage for pro- 

 tection on cold and stormy days. Here we find them crowding together in countless 

 numbers; until after a very brief period they engage in their work of destruction. 

 The young caterpillars always creep towards the extremities of the branches, led by 



Fig. 79. — Elin span-worm nioili, natural 

 size. — After Emerton, from Packjirrt. 



Fig. 



80. — Elm spaii-worm, natural .size.- 

 After Emerton, from Packard. 



