The Canadian Entomologist 126: 103-110 (1994) This study determined the importance of Ophiostomatales fungi in the biology of individual adult Ips sexdentatus Boem. in Scots pine. We investigated factors possibly involved in success of rearing without Ophiostomatales, such as the sterilization technique, the presence of antibiotics, and the absence of yeasts. After sterilization of pupae, 866 adult beetles were reared in the media; the proportion of Ophiostoma-free mature adults was 99.2% and total mortality was about 13%. The most preferred rearing method used sterilized pupae which moulted on moistened filter paper and were transferred individually to separate vials where maturation took place on a sterilized phloem medium.The weight and size of Ophiostoma-free mature adults from semi-artificial media and, after establishment in logs, their fecundity and length of their egg galleries, were compared with those of naturally contaminated mature beetles obtained from logs. With the exception of a higher weight observed for adults matured in semi-artificial media, no essential difference was observed between the two groups. Ophiostomatales do not appear to play an essential role in the maturation and fecundity of I. sexdentatus adults. Colineau, B., et F. Lieutier. 1994. Production d'lps sexdentatus Boem. (Coleoptera: Scolytidae) adultes indemnes d'Ophiostoma et cornparaison avec des adultes naturellement contarninks. The Canadian Entomologist 126: 103-1 10. ResumeLe but de cette Ctude est de dCterminer si les champignons Ophiostomatales jouent, au niveau des individus, un r61e important dans la biologie des adultes d'lps sexdentatus sur le Pin sylvestre. Le r61e de divers facteurs dans le succbs de 1'6levage en absence d'Ophiostomatales a CtC testC, tels la technique de stkrilisation, la prCsence d'antibiotiques et la prCsence de levures. La mCthode d'Clevage la mieux adaptke a Ct C de placer les nymphes stCrilisCes sur papier filtre humide pour la mue imaginale puis, immkdiatement aprbs celle-ci, de transfCrer individuellement les jeunes adultes dans des pilluliers contenant un milieu axCnique B base de phlobme, pour leur maturation. Aprbs stkrilisation des nymphes, 866 adultes ont Ct C ClevCs dans les milieux semi-artificiels. La proportion d'adultes mQrs non contamines par Ophiostoma spp. a atteint 99.2% et la mortalit6 totale a Ct C de 13 %. Le poids et la taille des adultes murs indemnes d'Ophiostoma, ainsi que leur fCcon-ditC et la longueur de leur galerie de ponte aprbs installation sur rondins, ont Ct C comparCs B ceux d'adultes contaminks obtenus B partir de rondins. A l'exception d'un poids plus ClevC pour les adultes ClevCs sur milieu semi-artificiel, aucune diffkrence n'a Ct C observCe entre les deux groupes. Les Ophiostomatales ne semblent donc pas jouer un r61e essentiel dans la maturation et la fCconditC des adultes d'lps sexdentatus.
To discover measurable parameters for detecting quality differences (with respect to reproduction) in insect populations, variations in temperature were utilized to obtain manifestation of quality at different levels. Rates of reproductive and associated processes such as yolk deposition, gallery excavation, and oviposition were measured in Dendroctonus rufipennis (Kirby) at four temperatures. Information presented here allows an estimation of D. rufipennis reproduction as affected by temperature. Among the various parameters measured the length of initial egg-free gallery and the number of eggs/unit productive gallery length and yolk deposition rate could be used to discriminate bark-beetle population quality. Rates of yolk deposition appeared most useful and widely applicable for this purpose.
Can. Ent. 113: 177-183 (1981) Spruce beetles (D. rufpennis) from a population homogeneous with respect to population quality were subjected to different degrees of competition at corresponding stages of their reproductive cycles by varying the spacing of individuals and by varying the time of introduction of individuals into the competitive environment. Competition effects increase with gallery accumulation, as suggested in previous studies, and result in subsequent reduction of gallery production and oviposition. Increase in individual beetle quality, however, confers increased powers of resistance to the competition effects. Initial egg-free length is an unsuitable attribute for comparisons of populations. Expression of reproductive efficiency is a dynamic population characteristic which varies over the reproductive cycle, and which may be readily estimated by measurement of yolk deposition rate. For comparing populations, such measurements would be more valuable when carried out before the onset of competition effects. Individuals with the highest quality at the start of the egg-production cycle exhibit the highest reproductive efficiency as conditions change.Des dendroctones de l'epinette (D. rufpennis) d'une population homogkne quant k la qualit6 des populations ont kt6 assujetties B divers degrks de concurrence B des Ctapes correspondantes de leur cycle de reproduction en variant l'espacement des sujets et le temps d'introduction dans ce milieu concurrentiel. Les effets de la concurrence augmentent au rythme de l'accumulation des galeries, tel que suggCr6 par des etudes anterieures et resultant en une diminution subskquente de la production de galeries et de la ponte. Toutefois, plus la qualit6 de chaque insecte augmente, plus s'accroissent les pouvoirs de rksistance aux effets de la concurrence. La duree initiale sans oeufs constitue une caractkristique inadequate pour comparer les populations. L'expression de la capacite de reproduction constitue une caractkristique des populations dynamiques, qui varie selon le cycle de reproduction et qui peut &tre facilement CvaluCe en mesurant la vitesse de d k g t des jaunes.Aux fins de comparaison des populations, de tels mesurages seraient plus valables si effectues avant le debut des effets de la concurrence. Les sujets dont la qualit6 est la meilleure au debut du cycle de production d'aeufs accusent la capacite de reproduction la plus &levee B mesure que les conditions changent.
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