SB 508 E5P^ Ent. ITi r g txriMs.. kA/[/v\.qa., ^(ojUaa^. ^ X pEft Insects InJMvioMS to the American Elm. \\v-'' !t}'tiom\!^leuenth Hepoi|t of Vei|mont $tate Boaqd of j\'fliiicultut|e. \ Insects Injurious : : TO THH : : AMERICAN ELM. ^ G. H. PERKINS, Ph. D. lit NOV 8 .0^0) /augus A^u I'ATKior .lois PuiNTiNO House J INJURIOUS IP^SECTS. G. II. Perkins, Ph. D. I'rofossor or Natural Jlistoi'^' in the Uiiiver.sity ot Vciniont. Eiilouiologifct to tl State Afjrrifiiltural Kxi)eriiuent Station. METHODS OF PREVENTING OR CIIECKL\(, THE ATTACKS OF INJURIOUS INSECTS.— 1. INSECT ENEMIES OF INJURIOUS INSECTS. Ill order that we may meet the attacks of destructive insects with any chance of success, it is necessary, iirst, that we understand something of the structure, liabits, and mode of development of each species ; and, second, that we be able to devise some method by which the enemy may be driven ofi, or, if possible, exterminated. Usually the war must be one of extermination, for, as every farmer 7m«L,only too well knows, insects when driven oft' very often return speedily, and with re-entorcement. Thus the study of insects^/of insecticides must be carried on together. New insects are every now and then appearing, some of them injurious, some beneficial, some neither. Most injurious insects are attacked in one way or another by other insects. These may be either parasitic upon eggs, larva, pupa or imago, that is, upon anv of the difterent stages which ordinarily occur in the life of insects, and sometimes an injinious insect is attacked in each of these stages by a difterent enemy. The sudden decrease in the niiml)er of insects, which every one has now and then observed, is often due to the destruction caused by parasitic insects. I remember a season some years ago, when canker worms were most ruinously abundant, so much so, that the citizens of the infested town were quite in despair eoncerning elms and other trees, and the ))rospects for the next season were certainly discouraginof ; but, to the agreeable surprise of everv one, the next season brought not only no increase of the canker worm, but so very marked a decrease as to well-nigh render cftbrts for the prevention of further damage to the trees unnecessar\', and, tor a number of years after this, there was no return of the pest. This deliverance was due to the attacks of certain parasites, which so eftectually destroyed the canker worms as to nearly dii\e them from the locality. So complete a removal of the evil does not, indeed, often occur, but most of our injurious insects are kept more or less in check by parasites. Some insects are attacked by three or four, or, it may be, ten or twelve parasites. It is obvious that an investigation of this subject of parasitism is of the highest importance. It is, ot course, a blind and bungling method of war- fare to fight against all insects indiscriminately. We must always remember that there are insects which are of value to the larmer, and the destruction of these is as great a mistake as it is to allow an injurious insect to escape. It is a most fortunate law which seems to prevail throughout the insect world, that vegetable-feed- ing insects, which are mostly injurious, are almost always attacked by one or more, sometimes many, parasites, and as the pernicious species increase, the parasite is very likely to increase, and often the latter' destroys the whole race of the former. It is not quite easy, without occupying too great space, to give definite descriptions of these parasitic insects which are our friends ; but the subject is one ol so much importance that, with the aid of the accompanying illustrations, an attempt will be made to give a general idea of some of the more common beneficial insects, although it will not be possii^le to give anything like a complete account of them, or to even mention more than a few. However, the ])rihcipal classes are illustrated. Not only parasitic, but preda- tory- insects, those which aie the lions and tigers of the insect world, going about seeking the bugs they would devour, must be noticed, and it is sincerely hoped that what information is herein given may be of some assistance in enabling the farmer to distin- guish his friends from his foes. The ichneumons, bristle tails, etc., mentioned and figured must serve as types of the groups to which they belong, and, although not strictly correct, yet it will on the whole be safe to consider all similar insects as friends ; for, while some of tiie gall-making insects, as may. be seen in figure 6, numbers 21 and 22, which are of this sort, very closely I'esemble some of the parasitic species, so that they are very likely to be mistaken for them, yet there are not many of them injurious to farm crops, nor likely to be seen about them. For this reason the insects of the sort under consideration which the farmer is most likely to come across, are his friends. Dragon flies devour many small insects, and in all the great groups into whicli entomologists divide the innnense kingdom of the insects, there are some which, l)y destroying their allies, become most valuable friends to man. Somcwhiit resembling in form and closely related entomolo- gically to the ill-smelling black scjuash hw^^ there are several insects which are most beneficial. Figure 1 shows the form of one of these, and figiu-e 2 an enlarged cut of another, which is popularly known as the Spiny Soldier Bug. It is one of the most useful predatory insects, devouring in the larval state plant lice in great num- bers, and when fully grown it attacks a great variety of inju- rious insects, some of them being among . , Figure 1. our most de- soi-mKR Bug. S t r U C t i V e Spe - Acanthocephala femorata. Gl. Si'iNY Soi.iMKK Bug. cies. Even the potato beetle finds an enemy Sinea mlthpinosa. De Geer. \\\ this inscct, as docs the Canker vvoriu and other pests. Figure 3 represents a fly devouring a lar\a which he has seized. Flies of this group, known as Asilus flies, are beneficial in destroying pernicious insects, but thev, unfortu- nately, do not confine themselves to those that arc harmfid, but often destroy many bees. Figure 4, as well as figures h and (I, illustrate a large group of small, often brilliant-hucd beetles, known as Tiger Beetles, and the name is signillcant of their habits. The\- mav often be seen lunniiig l)riskl\ oxer i)aths or roads in Figure 3. RoiiliKK Fl.V. Erax apicaii/is, 1 1 '. Figure 4. Tk:k.k iti'.iMi.K. Tt-ttacha Carolina, L. Figure 5. ri(a:u BKKri.K. Tetraclia I'in^inica, Hope. 6 bright warm davs. They devour many insects and are to be re- garded as beneficial. Figure G gives illustrations of several species of the Tiger Beetles and the larva, wilh the head of one of them enlarged. Figure 6. CicindelidcB — TiGER BEETLES. Beginning at the upper right hand corner the species are : Cicitidela hirticoUis, Say; Cic'nidela vulgaris, Say; Cicindela sexgiittata, Fabi. a. larva, b. head enlarged, c. beetle. (After Riley.) Figure 7 shows the larva and perfect insect of another and larg- er beetle of similar habits. It is not very uncommon, and is ex- ceedingly useful in destroying some of our most pernicious insects. The beetle is bronze-black, vs'ith light reddish bronze spots arrang- ed in rows, as seen in the figure. It is found under stones and in other sheltered places. Among other insects, it destroys the white hlv respect. It may seem an over enthusiastic outburst of admiration to say that the American elm is the finest shade tree known, and opinions may well differ in regard to this, but for myself I believe it to be true that, taking gracefulness, ease of cultivation, variety of form, adaptation to our climate and the physical features of the country, this tree is superior to all others. There are those that arc more delicate in leaf, more elegant in flower, more wonderful in this or that respect, but making up a general average, 1 think we shall find our elm coming out ahead of all the rest. It is rather strange that this tree, like most others, has as its worst enemies, for the most part, very small insects. There are a few large species that more or less commonly attack some part of the tree, but by far the larger part of those insects which injure it are small. This fact makes it all the more difficult to deal with the foes of the elm, since the large size of the tree and the small size of the insect ren- ders the concealment of the latter easy, and the great extent of siu'- face to be reached by an\ insecticide makes it difficult to apph it with sufficient thoroughness to be of use. 14 24 Moreover, many of the insects we are to study are insidious in their method of attack, and ere their presence is noticed, they are so far established that their removal is difficult. It is a fact that our elms are in danger ; some have already died, some are sickly from the attacks of insects, some less severely affected are yet infested, and on the way to ruin, so that it is none too soon to give attention to them. General remedies have been considered in the first part of this paper, and most of these are applicable to the elm, but it will be better to speak of specific remedies in connection with specific insects. In Europe over a hundred different species of insects have been described by entomologists which infest the European elm. A less number have thus far been found on the American elm, but in the list which is given on a following page, there will be found a sufficiently powerful array of foes to satisfy the most belligerent. In considering the damage which anv insect commits, we must have regard to both the time and method of attack. If an insect like the canker worm eats the leaves of a tree, the injury is greater if done in the early part of the season, as it always is, than it would if done later, so, too, since the living, growing parts of a tree are the new roots, twigs and leaves connected by the outer layer of wood and inner layer of bark, an insect which attacks these is more injurious than one which shouUl attack the heart-wood, and so on. The following list embraces all the different species of insects which, so far as I have knowledge, attack the elm. I am well aware that such a list is not very interesting in itself, but I hope that it may prove of value to some of those who may read this paper. With the scientific name the common name is given so far as possible. Many of the species have no other name than the scientific. In order to aid those unfamiliar with entomology in the use of the list, I have added after the name of each of the large groups under which the different species are enumerated, a few of the more familiar examples in order that some idea of the char- acter of the group may be gained. For convenience I have arranged the names alphabetically. 25 LIST OF INSECTS INJURIOUS TO THE ELM. IIYMENOPTERA. REES, ANTS, WASPS, ETC. Cinwcsamcricaua., Leach. Elm Saw-fly. 7 rcincx colm)iba^ L. Pii^con trcmex. lI':piik)ptera. MOTirs AND HUTTERFLIES. Auisoptcryx vcri/ata^ Peck. Canker worm. Anisoptcryx poiiictaria^ Ilarr. Fall Canker worm. Anthaxia virid/cor/fis^ Say. yXiiipJiidasys coo-///(aria^ Guen. Apatcia at)icrica)ia^ llarr. Apatcia i^risea^ VV^alk. Apatcia mor/t/a,Xj. i\m\ II. Arctia iiais^ Drury. Argyresthia anstcrella^ Zell. liitctra agiitaria^ Clem. Ccratoiiiia a/iiynfor^ llul). The Four-horned Ceratomia. Clisiocanipa auiericaua^ Ilarr. Tent caterpillar. Choerodes clcviitarta^ A. and S. Enipretia stimiilea., Clem. Epirritia dilitata^ Plub. Eitgonia siibsignaria^ Hub. Grapta interrogatioiiis^ Hub. Semicolon Butterfl)'. Grapta prognc^ Cran. Grapta co/niiia^ Ilarr. Halesldota carycc, Ilarr. Hyphantrla ciinca^ Drury. Fall Web-worm. Ilyperchiria. lo^ Fabr. Emperor moth. I-Iyberiiia tilaria^ Haw. Lagoa crlspata^ Pack. Llthocollctis ubnella^ Ciiam. Elm leaf primer. UtJiocollctis argciithiotcUa^ Cham. Li'/nacodes scaplta^ Ilarr. A/ctaneii7-a