The Pine-Bark Beetle, Hylastes ,Ater, in New Zealand
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NEW ZEALAND STATE FOREST SERVICE. CIRCULAR No. 33. A. D. McGAVOCK, Directol' of FoPestry, Reprint from Journal of Science and Technology, ·vol. XIV, No. 1. THE PINE-BARK BEETLE, HYLASTES ,ATER, IN NEW ZEALAND. BY ARTHUR F. CLARK, Forest Entomologist. WELLINGTON. W. A. G. SKINNER. GQVE,RNMENT PRINTER. 1932. NEW ZEALAND STATE FOREST SERVICE. CIRCULAR NO. 33. A. D. McGAVOCK, Director- of Forestry. Reprint from Journal of Science and Technology, Vol. XIV, No. 1, THE PINE-BARK BEETLE, HYLASTES ATER, IN NEW ZEALAND. By AB,THUR F. CLARK, Forest Entomologist, State Forest Service. INTRODUCTION. ALTHOUGH the Coleoptera is the best represented of any order in New Zealand, there are but few species of the family Ipidae. This is rather surprising when it is considered that the Dominion originally possessed very large areas of coniferous and hardwood forests, some four million acres of which still remain in their virgin state, and, further, that many species of other families of beetles associated with forests, such as the Cerambycids and Colydiids, are to be found. The arrival and establishment of Hylastes ater Payk., which is the first introduced Ipid beetle to become so estab lished, adds to the number of the native species, but is nevertheless a very unwelcome addition. Forestry conditions in New Zealand differ to some extent from those existing in the Old World, in that attempts to regenerate the native timber trees are still in their infancy. Whilst the planting of introduced tree species dates from the earliest days of settlement, during the last decade a programme of extensive establishment of introduced conifers has been carried out, with the result that more than 500,000 acres are at present under this type of forest, the greater part of which has been established since 1921. The planting has been undertaken by various authorities, such as the State, Plantation Boards, County Councils, com mercial concerns, and private individuals, but there is no legislation which gives the State any powers of supervision or of control of areas other than those which it directly administers. The majority, particularly of the more recently established areas, is planted in pure blocks, and of the species selected Pinus radiata Don. is easily the most favoured. The State owns approximately 160,000 acres of pure P. radiata, and commercinl concerns are responsible for a further 200,000 acres, both of these totals increasing annually. It can therefore readily be seen that the advent of any new forest insect, particularly if it attacks P. radiata, is not viewed with equanimity, and without doubt H. ater is the most serious of the introduced insects which at present attack this tree species. 2 A single specimen of a beetle was sent to the writer from Foxton, in the North Island, in August, 1929, and was accompanied by a small piece of a damaged seedling of P. radiata. Identification, which was later checked by the Imperial Institute of Entomology, did not prove difficult, and the writer left immediately for the scene of the outbreak. Here it was found that a small stand, mainly of introduced conifers, of which the greater part had been logged and replanted, was very heavily infested, the overwintering larvae and adults of H. ater being present in large numbers, the latter attacking the young trees. The plantation, although divided into several blocks, totalled only some 70 acres, and, being established upon a site the soil of which was almost pure sand, the question of the possible eradication of the insect by means of intensive destruction of stumps and other infested material was con sidered. The first step being the defining of the limits of the infestation, a rapid survey was made of an area having a radius of some ten miles, with the infested area as its centre. The survey revealed, unfortunately, that the beetle was established at many points throughout this area, and that the utilization of methods designed to effect its complete eradication was impracticable. As later investigations proved, the beetle was even then established in a large number of districts. A study of the behaviour of the beetle under New Zealand conditions, its potential powers oi damage, and means of controlling its activities was commenced. It is unfortunate that the investigation should have coincided, during its later stages, with a period of acute economic depression, which neces sitated the drastic curtailing of travelling and consequently the total abandonment of some experiments before they had been completed. Opportunity is taken of recording the writer's appreciation of the most valuable assistance in connection with field and sample-plot work given by Mr. J. F. Field, Senior Ranger, State Forest Service, Palmerston North. To Karl Schedl, of the Division of Forest Insects, Ottawa, Canada, the writer tenders his thanks for assistance in the interpretation of the male genitalia. Thanks are extended also to Miss H. V. Kirby, assistant photo grapher at the Cawthron Institute, for the excellent photographs forming figs. 10 to 14. Frequent reference will be found to the paper by Munro(l) upon the genus Hylastes, the detailed work by this author being an invaluable guide in the present investigation. Munro took H. ater as the type for his study, and but little, therefore, will be added upon the question of morphology, only the male genitalia and the proventriculus being briefly described and figured. SYSTEMATIC POSITION. Hylastes ater Payk. was described by Paykull(2) as Bostrichus ater. His original description, in Latin, translates as follows:- Glabrous, black, opa.que, elytra twice as long as broad, punctate-striate, interstices raised. Ilabitat.-Beneath bark 0£ pines. Head black, punctulate, deflexed, antennae rufescent. Thorax black, structurally similar to preceding species* but more densely and deeply punctulate. Scutellum punctiform, black. Elytra black, length twice width (width same as that of thorax), * Bostr. piniperda F. 3 convex-cylindric, puncta.te-striate, with numerous raised interstices. Wings pELle hyaline, veins indistinct. Feet piceous, tibia dilate serrate, tarsi less stout. Slightly smaller than the preceding species. Eyes fringed with very short sparse greyish pilosity. Observati'.ons.-Closely related to Cure. chloropus or Onrc. ater, but differing in the clubbed antennae, elytra less deeply striate, thorax shorter, tibia dilate serrate, com pressed. Sent formerly to Fabricimi, but his description in the reference by no means conforms. Variety B.-Piceous, dorsal surface of thorax, elytra, and feet ferruginous. Habitat similar to preceding. PaykuU gives the fo]Jowing references :- Fabr., Ent. Syst., l p., 2 p., 368, 20 : Bostr. ater ? Herbst., Col., [) p., III, 9, t. 48, 9 : Bostr. angustatirn. So far as can be judged, it seems that Paykull forwarded specimens to Fabricius(3), whose description is referred to by Paykull (Z.c.) but is queried by him. Fabricius (Z.c.) indicates in his description that his specimens were obtained from Paykull. Paylrnll has long been recognized as the author of Bostr. ater, although from examination of the literature alone it would appear that Fabricius has some claim. Fabricius(4) later moved his Bostr. (tter to his genus Hylesfrius, giving Bostr. ater Payk. as a synonym. Hagedorn(5) confuses matters somewhat by giving Hylesinus ater F. as a synonym of Hylastes ater Payk., which appears to be in favour of any claim that Fabricius may have. However, since the matter can only be satisfactorily investigated by reference to types, it must be presumed that this has long since been done. Erichson did not recognize Fabricius, so that when he erected his genus Hylastes in 1836 he took Bostr. ater Payk. as a type. Erichson's original description, in Latin, of his genus Hylastes, given by Hagedorn(6), translates as follows:- Antennae with 7-jointed funicle, club orbicular, compressed, 4-jointed. Tibiae extemally denticulate. Maxillary palps somewhat short, conical. J.,abium bare, simple, subcordate, labial palps jointed, lst joint largest, 2nd a third or less, indistinct. Antennae with scape elongate, 2nd joint globose, 3rd ohconicaJ, remainder short gradually widening. Body elongate or oblong, cyJindric. Rostrum distinct, pros ternum with deep a.nterior impression. Anterior coxae approximate. Swaine(7) briefly discusses the position of the genus, which is uncertain, and, while favouring its replacement by Toniicus Lat., he continues its usage solely upon the grounds that a change would cause confusion. DISTRTBCJTION AND STATUS IN OTHER COUNTRIES. During the last fifteen years H ylastes ater has been recorded from the following countries: England, Scotland, France, Germany, Spain, Italy, Norway and Sweden, Russia, and the central European States. It is. there fore, widely distributed throughout Europe generally, but is not, apparently, found in America or Canada. In Europe its status appears to have been obscured to some degree by the fact that the damage caused by H. ater was confused with that caused by the weevil Hylobiits abietis L., the latter insect being held responsible for damage caused by the former. Munro (Z.c.) appears to be the first to realize its true status, and gives a clear account of the damage caused by the beetle. In Europe H. ater is often recorded in association with other species of bark beetles and weevils commonly found in coniferous forests. Amongst these insects occur further species of the genus Hylastes, but, as none of its associates occurs as yet in New Zea] and, no confusion can arise here , regarding its status. H. ater is generally noted in Europe in a non-epidemic capacity, it then breeding in dead and dying standing trees; its status changes, however, as soon as it becomes associated with newly planted or replanted areas. The writer has not found many definite records upon a quantitative basis of the damage caused by H. ater in Europe, but Munro (l.c.) gives an account of an infestation in Scotland where out of ap proximately 60 per cent.