79 research outputs found
Identification of a Sex Pheromone Produced by Sternal Glands in Females of the Caddisfly Molanna angustata Curtis
In the caddisfly Molanna angustata, females produce a sex pheromone in glands with openings on the fifth sternite. Gas chromatographic analyses of pheromone gland extracts with electroantennographic detection revealed four major compounds that stimulated male antennae. These compounds were identified by means of gas chromatography–mass spectrometry and enantioselective gas chromatography as heptan-2-one, (S)-heptan-2-ol, nonan-2-one, and (S)-nonan-2-ol in the approximate ratio of 1:1:4:10, respectively. Field tests showed that the mixture of the two alcohols was attractive to males whereas addition of the corresponding ketones reduced trap catches. The sex pheromone of M. angustata, a species in the family Molannidae within the suborder Integripalpia, is similar to the pheromones or pheromone-like compounds previously reported from six other trichopteran families, including members of the basal suborder Annulipalpia. This suggests that minimal evolutionary change of the pheromone chemistry has taken place within the leptoceroid branch of integripalpian Trichoptera compared to the ancestral character state
Trees Wanted—Dead or Alive! Host Selection and Population Dynamics in Tree-Killing Bark Beetles
Bark beetles (Coleoptera: Curculionidae,
Scolytinae) feed and breed in dead or severely weakened
host trees. When their population densities are high, some species aggregate on
healthy host trees so that their defences may be exhausted and the inner bark
successfully colonized, killing the tree in the process. Here we investigate
under what conditions participating with unrelated conspecifics in risky mass
attacks on living trees is an adaptive strategy, and what this can tell us about
bark beetle outbreak dynamics. We find that the outcome of individual host
selection may deviate from the ideal free distribution in a way that facilitates
the emergence of tree-killing (aggressive) behavior, and that any heritability
on traits governing aggressiveness seems likely to exist in a state of flux or
cycles consistent with variability observed in natural populations. This may
have implications for how economically and ecologically important species
respond to environmental changes in climate and landscape (forest) structure.
The population dynamics emerging from individual behavior are complex, capable
of switching between “endemic” and “epidemic” regimes
spontaneously or following changes in host availability or resistance. Model
predictions are compared to empirical observations, and we identify some factors
determining the occurrence and self-limitation of epidemics
Weather factors influencing catch of Neodiprion sertifer (Hymenoptera : Diprionidae) in pheromone traps
Variation in number of European pine sawflies Neodiprion sertifer caught in pheromone traps during 11 d of the peak flight period was in part explained by weather. Daily average air temperature was the most important variable and explained 86% of the variation. A threshold for flight was c+11°C. Rain during most of the day inhibited flight, but occasional showers did not. -from Author
Mating disruption of the pine sawfly Neodiprion sertifer (Hymenoptera: Diprionidae) in isolated pine stands
1 Previous applications of the mating disruption technique to Neodiprion sertifer resulted in decreased numbers of males caught in the treated area but no effect on sex ratio or overall population density. 2 The present study assessed the efficacy of mating disruption against N. sertifer outbreaks in pine stands surrounded by agricultural areas or pasture, and therefore isolated from other infested areas. 3 Pine stands were treated by placing dispensers with an erythro-mixture of the acetate ester of 3,7-dimethyl-2-pentadecanol every 10 m in a grid. 4 The efficacy of this technique was evaluated by comparing the number of males caught in sticky traps baited with synthetic pheromone, and by comparing the sex ratio and the population density of the sawfly in the subsequent generation between treated and control pine stands. 5 The number of males caught within treated areas was significantly lower than in the control area. 6 In the treated pine stands 46% of the egg clusters resulted in male cocoons only, compared to 3% of the clusters in the control stand. 7 A significant reduction of the sawfly population was observed in the treated pine stands. The results contrast to the earlier mating disruption attempts with N. sertifer and can probably be ascribed to the isolation of the experimental stands
Ecology of the Dutch elm disease vectors Scolytus laevis and S. scolytus ( Coleoptera : Scolytidae) in southern Sweden.
Two rings of pheromone-baited sticky traps surrounded the elm wood at 20-300m and 1-2km outside the forest edge. Most Scolytus were caught at sites in the inner ring near the forest; <1% of the total were caught in the outer ring. Emergence from logs and trap catches showed a first peak in July. Flight activity was recorded from the end of May to September for both species. A 2nd peak of activity was evident in August in 2 of 3yr for S. scolytus.-from Author
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