366 



ARBORICULTURE 



337. Tussock moth larva. ( X 



members of several different groups of insects, certain 

 small moths, a few saw-flies and a small number of flies 

 and beetles. All of the leaf-miners are very small 

 insects whose larvse feed upon the parenchyma of the 

 leaf, leaving intact the upper and lower epidermis. 

 In this position they are protected from most sorts of 



insecticides, although 

 in some cases, spray- 

 ing with a contact 

 insecticide containing 

 some tobacco com- 

 pound in combination 

 with soap may be 

 efficacious. One form- 

 ula recommended is: 

 water, 800 gallons; 

 nicofume, or "blackleaf 

 40," one gallon; laun- 

 dry soap, thirty-two 

 pounds. Ordinarily, 

 leaf -miners do not pre- 

 sent a serious menace 

 to trees, but the pres- 

 ence of their blotch-like or serpentine galleries, which 

 show as faded areas, often greatly disfigure the leaves. 



Some of the more important shade-tree pests. 

 A. Defoliators. 



The tussock moth, Hemerocampa leucostigma (Fig. 

 337), is perhaps the most abundant caterpillar on trees, 

 particularly in thickly settled districts. The eggs are 

 laid in the fall in white fluffy masses the size of a dime 

 on the trunks of infested trees and hatch in the early 

 summer. The larvse bear several pencils of long black 

 hairs placed at each end and have four brush-like tufts 

 of pale yellow hairs above, with a bright red head. 

 These pupate early in July in crevices in the bark and 

 the adults soon emerge to lay the eggs for a second 

 generation of caterpillars which will mature before fall 

 into moths that deposit the over-wintering eggs. The 

 female moth is without wings and lays her mass of 

 eggs on the bark where she emerges from her pupa 

 case. These caterpillars feed on all sorts of trees 

 except evergreens, but seem to be most destructive to 

 maple, elm and American linden. Two related caterpil- 

 lars have been imported from Europe into Massachu- 

 setts, the gypsy moth and brown-tail moth, and 

 although these are at present confined to that neigh- 

 borhood, they will undoubtedly become widespread 

 before many years have elapsed. The gipsy caterpil- 

 lars feed on many kinds of trees, preferring oaks; they 

 may be recognized by a double 

 line of round spots down the mid- 

 dle of the back, blue, followed by 

 red ones. Their life-cycle is like 

 that of the tussock moth, except 

 that there is only one generation 

 passing the winter as a mass of 

 woolly, dull ochre-yellow eggs at- 

 tached to the bark. The brown- 

 tail is a brownish caterpillar -with 

 white spots, passing the winter in 

 small woven silk nests containing 

 many caterpillars. The nests are 

 attached to the tips of the twigs 

 of infested trees. Orchard trees suffer most severely 

 from this species, although all sorts of broad-leaved 

 trees are attacked. 



Another common caterpillar of very different habits 

 is the American tent-caterpillar, Malacosoma ameri- 

 cana. This is an inconspicuous brownish moth which 

 over-winters as a band-like mass of eggs placed around 

 twigs of cherry and a number of other trees. These 

 hatch in very early spring and the larvae spin silken 

 nests in small forks of the branches from which they 

 crawl out to feed upon the opening leaves. They mature 



338. Cocoon of bag- 

 worm. ( x H) 



339. Euvanessa antiopa. 



ARBORICULTURE 



in early summer and the eggs are laid in midsummer for 

 the next season's brood. 



The bag-worm, Thyridopterix ephemeryformis, is a 

 defoliator at times very destructive, although each 

 larva in his dependent bag does not have a wide range 

 of operations. Fig. 338. Hand-picking and arsenical 

 sprays are the remedies. 



The caterpillars of the mourning cloak, Euvanessa 

 antiopa (Fig. 339), are a very common pest of elm and 

 other shade trees. They are black, coarsely spiny cat- 

 erpillars with red spots along 

 the back, and feed more 

 or leas in colonies, usually 

 defoliating single branches at 

 a time. The butterfly passes 

 the winter as an adult, ap- 

 pearing in very early spring, 

 and laying its eggs in May. 

 The caterpillars from these 

 eggs become full-grown be- 

 fore July, and the butterflies 

 of another generation appear 

 in July to lay eggs which will give rise to the hibernating 

 butterflies of the next winter. 



A common saw-fly which occurs on willows is the 

 American saw-fly, Cimbex americana. The larvae are 

 much like the defoliating caterpillars of moths and 

 butterflies in appearance and feed in the same way, 

 destroying the entire leaf-tissue. The larvae are pale 

 green, with a blackish line down the back. When 

 mature, they descend to the base of the tree, where they 

 spin parchment-like brown cocoons in which to pass the 

 winter on the ground among fallen leaves. In the spring, 

 they transform and the adult saw-flies deposit their eggs 

 singly in slit-like cuts made into the tissue of the leaf. 



Pine trees often suffer from the depredations of 

 saw-fly larva; of the genus Lophyrus which devour the 

 needles, near the bases of which they later spin their 

 small cocoons. 



Many saw-fly larvae feed only on the leaf from one 

 side, leaving the epidermis of the other side intact. 

 Arsenical sprays for the destruction of such species 

 must be directed against the side of the leaves attacked, 

 usually the under surface. 



Among defoliating beetle larvae, the imported elm- 

 leaf beetle, Galerucella luteola (Fig. 340), is probably 

 most important. This occurs only in the eastern 

 states but is gradually spreading into the middle West. 

 The small, yellow, two-striped adults live through the 

 winter and deposit their bright yellow eggs in small 

 masses on the under side of elm leaves in early spring. 

 These eggs hatch into black and reddish slugs which 

 feed on the under surface of the leaves, leaving only 

 the veins and upper epidermis. The leaves then dry up 

 and may fall off. The larvae, 

 now changed to a yellow color, 

 descend to the surface of the 

 ground to pupate and soon 

 emerge as a summer genera- 

 tion of beetles. There are 

 two or three annual broods, 

 according to the latitude. 



B. Plant-lice and scale insects. 



There are many kinds of 

 plant-lice (Fig. 341), but all 

 pass through very similar life- 

 cycles. In general, this is as 

 follows: the winter is passed 



as a large shining elongate- beetle . Ho les made by adults, 

 oval egg attached to a twig surface marks by , arvae . 

 or branch. This gives rise 



in the spiing to a soft-bodied wingless female aphid 

 that gives birth to living young aphids, which in turn 

 reproduce in the same way. These suck the juices from 

 leaves, petioles or tender twigs and thus sap the vital- 



340. Larvae 



elm-leaf 



