NATURE 



217 



THURSDAY, JULY 9, 1891. 



THE UNITED STATES ENTOMOLOGICAL 

 COMMISSION. 

 Fifth Report of the United States Entomological Com- 

 mission on Insects Injurious to Forest and Shade Trees. 

 By Alpheus S. Packard, M.D., Ph.D. 



VERY valuable Reports have been presented by the 

 United States Entomological Commission from 

 time to time. Among these may be mentioned that upon 

 " The Rocky Mountain Locust," prepared by Prof. Riley 

 in 1878, which is a most exhaustive record of the habits 

 of this terrible pest, and of methods of prevention 

 and remedies against its attacks. Later on, an equally 

 valuable and instructive Report was submitted with 

 regard to the cotton worm {Aletia argillacea), very 

 destructive to the cotton plant, whose crop it has re- 

 duced in some seasons from 30 to 75 per cent, in 

 the principal cotton-producing States. Both these ela- 

 borate works, as might be expected from their authors, 

 Prof. Riley and Dr. Packard, who practically constituted 

 this Entomological Commission, are full of interesting 

 experiments, ingenious contrivances, and subtle devices, 

 to circumvent the insect hordes advancing with the 

 insistance of invading armies. 



This Report upon " Insects Injurious to Forest and 

 Shade Trees" is perhaps not so exciting or painfully 

 interesting, as the harm caused to trees is not so directly 

 felt as that occasioned to various food crops and other 

 crops of the field by locusts and caterpillars innumerable, 

 and the name of the insects described therein is legion, 

 and their individual mischief is comparatively small. 



As Dr. Packard says, " a volume could be written on 

 the insects living on any single kind of tree, and here- 

 after it may be expected that the insect population of the 

 oak, elm, poplar, pine, and other trees will be treated of 

 monographically." Kaltenbach, in " Die Pflanzenfeinde, 

 aus der Klasse der Insekten," gives accounts of 537 

 European species of insects injurious to the oak, 107 to 

 the elm, and 396 to the willow. Perris, a French ob- 

 server, has recorded no less than 100 species of insects 

 found upon the maritime pine. 



The attacks of insects upon forest trees and upon 

 shade trees, or trees planted for shade and ornamenta- 

 tion in parks, streets, and other public places, are be- 

 coming far more numerous and serious, just as in the 

 case of all cultivated crops under the sun. In the United 

 States these attacks are creating intense interest, as the 

 forests are of the highest commercial importance, and 

 have been extensively decreased by clearing, by wanton 

 and accidental fires, and other causes. This Report, then, 

 is opportune, and must be of great service, as it demon- 

 strates the sources of the injuries, and suggests means of 

 preventing them or of diminishing them. 



The French, German, Austrian, and Italian Depart- 

 ments of Agriculture are giving much attention to this 

 subject, for it is found that the forest trees of these 

 countries are becoming more liable to harm from insects. 

 In Great Britain some kinds of trees, notably of the 

 pine tribe, have suffered much damage from insects 

 hitherto unknown, or, at least, not reckoned as injurious. 

 NO. 1 132, VOL. 44] 



There are, without doubt, many others unsuspected in 

 British woods and forests, slowly but surely working 

 great mischief. 



Dr. Packard shows that trees are attacked in every 

 part and in every conceivable manner by insects. Their 

 roots, leaves, bark, fruit, and twigs are all more or less 

 subject to their visitations. The most curious of those 

 which affect the roots is the " seventeen year " Cicada, 

 whose larvae remain for over sixteen years attached to 

 the rootlets of the oak, other forest trees, and fruit trees, 

 as the pear and apple. According to Prof. Riley, these 

 larvae are found at a great depth, sometimes as much as 

 10 feet below the surface. The female, resembling a 

 locust, deposits long slender eggs in an unbroken line 

 upon the terminal twigs of oak and other trees in May 

 and June. Sometimes the twigs are so "badly stung" 

 by this oviposition that the trees are seriously injured. 

 The length of wood perforated on each branch sometimes 

 varies from one to two and a half feet, averaging probably 

 eighteen inches, and appearing to be the work of one 

 female. From the eggs the larvae hatch out in six 

 weeks and drop to the ground, in which they live, sucking 

 the roots of the trees for nearly seventeen years, the pupa 

 state lasting but a few days. 



A formidable enemy of the "live-oak" {Quercus virens) 

 is an enormous beetle, Mallodon melanopus, Linn. , whose 

 larva, three inches long and an inch in thickness, bores 

 into the roots upon which it lives. As a result of the 

 work of this insect in South Georgia and Florida, " vast 

 tracts, which might otherwise have become forests, en- 

 riching the ground with annual deposits of leaves, are 

 reduced to comparatively barren scrub, in which the 

 scattered oak-bushes barely suffice to cover the surface 

 of the sand." The eggs are laid by the beetle in the 

 foot, or collar, of the tree, just below the surface of the 

 ground. It is not known how long the larvae live, but 

 their life must extend over several years, " since the 

 roots occupied by them grow to a large size, while they 

 show an abnormal development, and become a tangle of 

 vegetable knots. In fact, the entire root in its growth 

 accommodates itself to the requirements of the borer 

 within." The effect on the tree is to kill the original 

 stem, which becomes replaced by a cluster of insignificant 

 and straggling suckers, forming, perhaps, a clump of 

 brushwood. 



Among the tree-borers, other than beetles, the oak 

 "carpenter worm," the caterpillar of Prionoxystus 

 robinice, Peck, is the largest and most destructive. It 

 is larger and far more abundant than the European 

 caterpillar of Cossus ligniperda, or goat-moth, belonging 

 to the same family of Cossidae, but it sinks its tunnels deep 

 in towards the heart of the tree, not confining its mis- 

 chief to the limbs and large branches like the goat-moth 

 caterpillar. Fitch says of this : — " Of all the wood-boring 

 insects in our land, this is by far the most pernicious, 

 wounding the trees most cruelly. The stateliest oaks in 

 our forests are ruined, probably in every instance where 

 one of these borers obtains a lodgment in their trunks.'' 

 Another species of Cossus, known as Cossus centcrensis^ 

 bores into poplars. Its appearance and habits also resemble 

 those of the goat-moth, well known in this country. 



There are numbers of boring beetles, of the families 

 Buprestidae, Cerambycidae, and Scolytidae, whose larvae 



