This paper discusses insects which inhabit the cones o f white spruce,An attempt is made to bring together in one treatise the available information on all the insects causing primary injury to white spruce cones in Ontario and Saskatchewan. Previously, descriptions and habits of the principal cone insects, namely the spruce seedworm, Laspeyresia youngana (Kft.) (Tripp, 1954b), the cone maggot, Pegohylemyia anthracina Czerny (Tripp, 1954a). and gall midges (Cecidomyiidae) (Tripp, 1955) were published. In this paper the emphasis is placed on that part of the general biology pertinent to their ecology, and resulting damage to the seed. Consideration is also given to undeveloped or hollow seed because of its effect on the insect community and its economic significance. Cone insects less frequently encountered or those that do not contine themselves to a single cone are only casually treated. THE CONE AS A WITATThe cone is a compact unit and is thus readily studied as a community habitat. The insects inhabiting this restricted environment each have distinctive behaviors and in some cases quite restricted micro-habitats. It is, therefore, befitting that this paper begin with a description of the cones.A mature white spruce cone is elongate, ellipsoidal, and about 1.5 inches For personal use only.
This work, designed to provide an estimate of the quantity of food consumed by spiders, was part of a more general study of the ecology of a spider population in a stand of oaks (Quercz~s robw L.) in Wytham Wood, Berkshire, England (Turnbull, 1960a(Turnbull, , 1960b. Linyphia triangularis (Clerck) was selected as a test spider for the following reasons: it is a common, easily recognized, and easily acquired species; its size closely approximates the mode size of spiders in the population under observation; as far as it may be said of any spider, L. triangularis possesses few specialized features or habits; and the species is amenable to laboratory rearing and manipulation. Methods and MaterialsExperimental spiders were obtained from egg-sacs collected in the autumn, stored over winter at 4"C., and incubated in early spring at 25°C. and 75 per cent relative humidity until the spiderlings commenced to emerge and formed a dense cIuster around the emtpty egg sac. These clusters were then removed from the incubator, placed separately In rearing cages, and kept at room temperature and humidity. After t1x70 to 'three dam the spiderlinss dispersed tluoughout the cage on silken strands. About ter; days lxter they became increasingly active and a dense network of silk nSas constnicted. First prev were captured and some cannibalism was observed, whereupon the spiders were isolated into separate cages. Those that failed to construct a typical web within 24 hours of isolation were discarded.Rearing cages consisted of cvlindrical glass jars two inches in diameter and three and a half inches deep, with cotton gauze tops. Moisture was supplied )by dropping water onto a one-inch-thick plaster-of-paris pad in the bottom of each jar. No free water was waplied. Approximately 35 per cent relative humidity, estimated hv a strip of cobalt chloride impregnated paper in each jar (Solomon, 1945), uras'maintained in all cages. Jars were placed on one side in shelves exposed to room temperatures that ranged from 12'C. to 27'C. over the experimental period of about seven months. Dailv rearrangement of cages on the shelves minimized possible effecs of variations of light intensities and temperatures over different parts of the shelves. All spiders were reared simultaneouslv, so all were exposed to similar environmental conditions. The feeding behnviour of linvphiid spiders has been described by Norgaard (1943). In thcsc tests all spiders m&re fed living adults of Drosophila melamogaster Mg. Care mas talten to use onlv freshlv emerged flies of the F1 generation from each rearing bottle. Nine feeding regimens were established in each of which a number of spiders were provided wirh 3 fised number of flies each day as follo~vs: 0.5 flies per day-(one flv everv two days) to each of 36 spiders; one flv per day to each of 36 spiders; 1.5 hies per c!av ( 3 flies every mro days) to each (if 36 spiders; 2.5 Aies per dav (5 flies everv Z'davs) to each of 36 spiders; 3 flies per dav to each of 18 spidkrs; 4 flies per-day tieach of 36 spiders; 5 flies pe...
For more than a decade the sawfly, Neodiprion swainei Midd., has been a serious defoliator of jack pine, Pinus banksiana Lamb., in the Province of Quebec. In 1955 an intensive research program involving several research officers was initiated at the Forest Biology Laboratory, Quebec, to study the insect. Investigations began near the centre of the infestation at the headwaters of the Gatineau River (47° 55′N., 75° 25′W.). The project dealing with the parasites became the responsibility of the author and constituted approximately 25 pcr cent of the total investigations. Integrated with this project were studies on population dynamics, effect of defoliation on jack pine, and predators of the sawfly with emphasis on the small mammals. The primary object of the parasite studies was to concentrate on the life cycles and descriptions of the immature stages and to publish on each species as sufficient information was obtained. Ultimately, it is planned to publish jointly with other members of the team on the role of parasites in the overall mortality complex of Neodiprion swainei.
Maggots of Pegohylemyia sp. have been found inhabiting the cones of white spruce, Picea glauca (Moench.) Voss, in southern Ontario. The species was identified from a single male specimen as probably Pegohylemyia anthracina Czerny by the Swedish authority Dr. O. Ringdahl. Difficulty in rearing the maggots to the adult stage has delayed confirmation of this identification but it is expected that a good series of adults will be available shortly. In this paper, however, the emphasis is placed on the instars with an outline of the life cycle. It is shown that the second- and third-instar larvae are free-living, but the first-instar larvae moult to the second within the egg chorion.
Can. Ent. 104: 1003Ent. 104: -1016Ent. 104: (1972 Field studies enabled, the identification of some limiting factors to which parasitoids were exposed in exploiting the sawfly host, Neodiprion swainei Middleton, and aspects of their quantitative and qualitative impact on the host population. Emergence patterns and flight activity of parasitoids in the spring indicated that larval parasitoids were vulnerable to hyperparasitism by cocoon parasitoids. Although cocoon parasitoids were limited by a shortage of time in which to exploit the host in the spring they still reduced the overwintered host population by 66% in 1969. All forms of predation caused less than 10% sawfly mortality so parasitoids formed the major mortality factor in the spring. Sawfly in prolonged diapause appeared to be immune from cocoon parasitoid attack and thereby efficiency of these parasitoids was limited. However, cocoon parasitoid activity was selective on sawfly that would normally have emerged early in the season and thus delayed the average development of the host population. The complex food web based on the sawfly host provided a sensitive buffering mechanism to produce a degree of stability in the host-parasitoid interaction.The composition of the parasitoid faunae before and after establishment in N.swairlei populations of the introduced Pleolophus basizorrus (Gravenhorst) indicates the rapidity with which the parasitoid became influential in the complex.Des Ctudes conduites en for&t ont permis d'identifier quelques uns des facteurs de rCgulation confrontis par les parasito'ides en colonisant la Tenthrkde de Swaine, Neodipriorz swair~ei Middleton, et d'ilucider certains aspects d e leur impact quantitatif et qualitatif sur la population de I'hBte. D'aprks les modes d'tmergence et I'activitC atrienne de ces parasito'ides au printemps, leurs larves Ctaient sujettes B l'hyperparasitisme par les parasitoi'des du cocon. Encore que leur colonisation de I'hBte fiit de courte durte au printemps, les parasito'ides du cocon en 1969 n'en riduisaient pas moins de 66% la population de 1'hBte aprks I'hiver. Toutes les formes de prtdation n'ayant dttruit que moins de 10% des TenthGdes, les parasitoides constituaient donc le principal facteur de mortalit6 au printemps. En Ctat de diapause prolongCe, la Tenthrkde semblait immuniste contre I'attaque des parasito'ides du cocon, d'ou limitation de I'efficacitt de ceux-ci. Toutefois, I'activitC des parasitoides du cocon s'avtrait stlective sur la Tenthrtde qui, normalement, aurait tmergt plus tBt dans la saison et par ainsi retard6 le dtveloppement moyen de la population de I'hBte. Le tissu nutriciel complexe fix6 sur la Tenthr6de-h6te constituait un mtcanisme tampon conftrant un certain degrC de stabilitt B l'interaction de 1'hBte et des parasitoides.
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