Three specific DNA probes were used for the detection of the nuclear polyhedrosis (NPV) virus of Lymantria dispar (Ld NPV) genome. Two of these probes, H2 and H3 were obtained by classical cloning method and one (TR6) by polymerase chain reaction (PCR). These probes, used individually or in a pool in the standard slot-blot hybridizations, were able to detect 10(9) genome copies. By performing 35 cycles of PCR amplification before hybridization with primers specific to Ld NPV genome on DNA extracted from infected larvae, the sensitivity of the hybridization technique was increased, so that as little as 10 copies of the Ld NPV genome could be detected. Using these methods, L. dispar naturally infected by Ld NPV were identified among field populations in Canada and in the United States near the eastern Canadian border. Using a combination of PCR and hybridization, Ld NPV contamination of egg masses were also detected. By disinfecting the eggs with sodium hypochlorite prior to PCR amplification and hybridization, it was also demonstrated that transmission of viral infection in the natural populations is mainly caused by external contamination of the egg and is unlikely to occur through the transovarial route.

The formulations TSW (tansy essential oil, surfactant, distilled water) and TSWD (tansy essential oil, surfactant, distilled water, dillapiol) increased the feeding rate of oblique-banded leafroller (OBLR) larvae with increasing concentrations of tansy essential oil. When tansy essential oil was continuously present at 0.1% and 1% in the diet, all OBLR larvae from susceptible and resistant populations died. The presence of 0.01% tansy essential oil in the diet affected female pupal weight, but not larval weight gain, larval developmental time and male pupal weight. Our results suggest that the concentration of tansy essential oil that significantly affects the developmental variables should be between 0.01% and 0.1% of tansy essential oil. Residues of the formulation TE (tansy essential oil, ethanol 95%) deterred oviposition of OBLR female.

Head capsule widths of 10,677 larvae of the gypsy moth, Lymantria dispar L., from different populations in Quebec were measured and compared with those observed in Massachusetts 90 yr ago. Mean head capsule widths for each of the six instars were almost identical to those observed 90 yr earlier. Larval growth ratios decreased with molt number in all populations studied. This disagrees with Dyar's hypothesis, which proposes a geometrical head capsule growth in Lepidoptera. Populations that showed the greatest departures from Dyar's hypothesis suffered the highest levels of natural mortality. Parasitism and NPV infection are suggested as stressing factors that could have modified gypsy moth larval growth.

Observations during spring 1980 in two temporary pools near Trois-Rivières, Quebec, and in the laboratory show that Dipterian chironomid larvae can go through the gelatinous envelopes of egg masses of the salamander Ambystoma maculatum and consume developing eggs and embryos. In the clear water pool, egg spawns are heavily infested by the chironomid Parachironomus cf. forceps and embryonic mortality reaches 70 to 100%. In the dark water pool, infestation by an unidentified chironomid is low and embryonic mortality reaches 8%. In both cases, chironomid larvae leave the egg masses some 9 days before hatching of the salamanders. Fortuitous exploitation of a readily available resource is hypothesized; the frequency and precision of the observed phenological coincidence, due to the presence of other syntopic amphibian spring breeders, will be examined further.

RésuméUn inventaire de trois années (1972 à 1974) effectué à 178 stations réparties dans le Québec méridional a révélé la présence de 30 espèces de culicides. Pour deux de ces espèces (Aedes decticusetC.melanura) il s’agit d’une extension d’aire. Les types de gites larvaires où ces deux espèces ont été trouvées sont présentés et caractérisés par la végétation.

L'étude des gîtes culicidiens entreprise dans la région de Trois-Rivières nous a permis de mettre en évidence pour la première fois au Québec le parasitisme de l'espèce printanièreAedes (Ochlerotatus) excrucians(Walker) par une microsporidie (Nosematidae).

L'étude des conditions physico-chimiques de quelques gîtes culicidiens a été effectuée au printemps 1972 en Basse-Mauricie, Québec.Des mesures de température, d'oxygène, de gaz carbonique et de pH ont été réalisées. Ces mesures ont permis de mettre en évidence une relation étroite existant entre les conditions de température et d'oxygène dissous caractéristiques de la fonte des neiges et les variations d'abondance relative de 14 populations de culicides, Aedes communis, A. intrudens, A. impiger, A. fitchii, A. decticus, A. punctor, A. diantaeus, A. exerucians, A. trichurus, A. dorsalis, A. cinereus, A. riparius, A. vexans, A. atropalpus.