Two Njsw Shade-Tree Pests. 6i 



younger leaves, and a few larvae had already nearly completed their mines. I 

 have never seen the flies mating, and have found no males. Thus the insect 

 yearns to breed parthenogenetically. A small, thrifty tree which was putting 

 out much new growth in 1904, was severely attacked in June while older trees 

 nearby suffered but little, until about a month later. 



The egg is about .3 mm. in diameter, round, thin-shelled and of a deli- 

 cate rhilky-white appearance. The female sawfly saws a slit in the leaf from 

 the upper surface and tucks her egg in just under the upper epidermis of the 

 leaf. Most of the eggs are laid in the central portion of the younger leaves 

 between the larger veins. It requires about a minute to lay an egg. Over 

 the egg the surface of the leaf is slightly elevated and turns yellowish, thus 

 enabling one to easily locate the egg (Fig. 28) ; this is more distinctly seen 

 from the upper surface of the leaf. Evidently the eggs hatch in a few days 

 and the little larvae begin their life 1 as miners. 



The greenish-white, slightly flattened, distinctly segmented larvae with 

 light brownish heads and short apparently useless legs are shown much 

 enlarged in Fig. 24. The duration of the larval period I have not determined, 

 but it is probably about three weeks.* One larva mines over an elongate 

 area, about the size of a one cent coin, which is often bounded by two large 

 veins for some distance ■ before it merges into a neighbor's mine (Fig. 29), 

 Frequently the rusty brown ' ' blisters "or mines of ten to twenty larvae coalesce 

 and involve nearly the whole leaf, which soon dies. The excrement and 

 cast skins of the larvae are left within the mines. When full grown the larvae 

 burst through the upper epidermis of the leaf or the roof of their home, and 

 fall to the grdund into which they work themselves for a short distance, usually 

 about half an inch, sometimes an inch, and there make their thin, brown 

 papery cocoons. In summer they soon transform in these cocoons, probably 

 in a week or two, into the black sawfiies. 



Eggs are soon laid and another brood of larvae begin their destructive 

 work of " blistering " the leaves. I have not been able to determine definitely 

 the number of broods of this sawfly which develop during the growing season, 

 as the broods overlap, but there are at least two or three broods, perhaps more. 

 Beginning in May, their work continues throughout the summer until October 

 in this latitude. After about June 1st, I have found the insect in all stages 

 on or under the infested trees almost any day until September. This is in 



*Dyar has described in detail six larval stages (Can. Ent., XXV, 247). In the fifth 

 or last feeding stage, the larva is translucent whitish with a greenish tinge from the food, 

 and it measures 6 to 7 mm. The head is much flattened and of a light brown color with 

 the mandibles and ocelli darker. The true legs, the ventral surface of the first thoraic seg- 

 ment, small spots on the venter of the other thoraic segments, and the cervical shield are 

 brownish. The abdominal legs are rudimentary and present on joints 5 to 12. No tuber- 

 cles or setae are distinguishable. I have found no striking differences between these larvEe 

 and those of the European elm sawfly leaf-miner, Kaliosysphinga dohrnii, therefore Fig. 6 

 may represent both species. 



