Seasonal Abundance of Temnochila chlorodia (Mannerheim) (Coleoptera: Trogositidae) Collected in Western Pine Beetle Pheromone-Baited Traps in Northern California

Bark beetles (Coleoptera: Scolytidae) are commonly recognized as the most important mortality agent in western coniferous forests. In this study, we describe the abundance of bark beetle predators collected in multiple-funnel traps baited with exo-brevicomin, frontalin and myrcene in northern California during 2003 and 2004. A total of 32,903 Temnochila chlorodia (Mannerheim), 79 Enoclerus lecontei (Wolcott), and 12 E. sphegeus (F.) were collected. The seasonal abundance of E. lecontei and E. sphegeus was not analyzed because too few individuals were collected. In general, T. chlorodia was most abundant in late spring, but a second smaller peak in activity was observed in late summmer. Overall, the ratio of males to females was 0.82. A significant temporal effect was observed in regard to sex ratios with more males collected during later sample periods. Temnochila chlorodia flight activity patterns were similar between years, but activity was generally delayed several weeks in 2003.

COMPARATIVE TOXICITY OF LINDANE, CARBARYL, AND CHLORPYRIFOS TO THE WESTERN PINE BEETLE (DENDROCTONUS BREVICOMIS) (COLEOPTERA: SCOLYTIDAE) AND TWO OF ITS PREDATORS, ENOCLERUS LECONTEI (COLEOPTERA: CLERIDAE) AND TEMNOCHILA CHLORODIA (COLEOPTERA: TROGOSITIDAE)

Each of three insecticides—lindane, carbaryl, chlorpyrifos—was tested by topical application on the western pine beetle, Dendroctonus brevicomis LeConte, and two native coleopterous predators, Enoclerus lecontei (Wolc.) and Temnochila chlorodia (Mann.), to assess comparative toxicity. Lindane was more toxic to the predators than to western pine beetle, while carbaryl was relatively non-toxic to E. lecontei when compared with either T. chlorodia or western pine beetle. Chlorpyrifos was equally toxic to all three species. Results of topical application serve to estimate relative effects of insecticides on predacious associates in the western pine beetle community.

THE ARRIVAL SEQUENCE OF THE ARTHROPOD COMPLEX FOLLOWING ATTACK BY DENDROCTONUS BREVICOMIS (COLEOPTERA: SCOLYTIDAE) IN PONDEROSA PINE

Continuous trapping on the bark surface of Dendroctonus brevicomis LeConte infested trees in the central Sierra Nevada mountains was undertaken with the objective of determining the spatial and temporal arrival patterns of the natural enemies and other insect associates of the western pine beetle. Over 100 species of D. brevicomis associates were collected and patterns of arrival were described for many of these. The main bark beetle predators were trapped during D. brevicomis mass arrival and shortly thereafter. Enoclerus lecontei, Temnochila chlorodia, and Aulonium longum, all predaceous beetles on D. brevicomis adults and larvae, were among the first species to arrive, as was Medetera aldrichii (Diptera), a larval predator. The bark beetle parasites Roptrocerus xylophagorum and Dinotiscus (=Cecidostiba) burkei (Hymenoptera) were well synchronized with the beetles’ life cycle as they arrived late in the beetles’ larval stages when suitable hosts were available.Approximately twice as many associates were trapped in the first (spring) beetle generation as in the second (fall). Differences between species with regard to height distribution were common, and these often varied with seasonal beetle generation.Calculations of changes in species diversity through time, of the associate complex trapped at the bark surface, were made for both the first and second beetle generation. Linear correlation analysis indicated a highly significant increase in species diversity occurred from the time of the beetles’ mass arrival until brood emergence. This increase may correspond to an increase in diversity of the structure of the subcortical community, as more insect species arrived and progressively modified the habitat of the newly killed tree.

PHEROMONES OF IPS PINI (COLEOPTERA: SCOLYTIDAE): VARIATION IN RESPONSE AMONG THREE POPULATIONS

Reciprocal field tests of attraction between populations of Ips pini (Say) from California, Idaho, and New York disclosed geographic variation in pheromone systems. These differences reside both in pheromone production and reception. However, it is unknown whether variation in the pheromone bouquets is qualitative, quantitative, or both.In New York, both sexes responded in higher numbers to their own pheromone than that produced by California or Idaho males. In California, beetles of both sexes discriminated against New York, but in Idaho only females made this distinction. In both California and Idaho, the local population showed a slight preference for the pheromone produced by Idaho males over that produced by California males.The predator Enoclerus lecontei (Wolc.) demonstrated a four-fold preference for attractants produced by males from New York over those produced by beetles from California and Idaho. The parasitoid Tomicobia tibialis Ashmead showed the opposite trend.There is no evidence that geographic variation in the pheromones produced by I. pini is sufficient to enforce breeding isolation between adjacent populations. However, these results dramatize the necessity of considering pheromonal variability in programs applying pheromones for the survey and control of widely distributed pests.

Factors Influencing Oviposition, and the Effect of Temperature on Development and Survival of Enoclerus lecontei (Wolcott) Eggs

The factors influencing oviposition and feeding of Enoclerus lecontei, and the effect of temperature on egg development and survival, were studied in the laboratory.When food was not a limiting factor, the total number of eggs laid, and the total number of bark beetles consumed by clerid pairs during their lives was strongly influenced by longevity of the female and to a lesser extent by female “vigor”. Female “vigor” and longevity were not necessarily coincident. The rate of oviposition and the rate of food consumption are mainly influenced by the “vigor” of the female clerid.The effect of suboptimal food on oviposition was determined. Regression equations are given for estimating the number of eggs laid utilizing three measures of food supply, number of bark beetles supplied, their weight, and number eaten. The independent variables may be used separately or combined as a multiple regression.Time for egg development varied from 5 days at 35 °C. to 28 days at 15 °C. Optimal conditions for development and survival were between 20° and 25 °C. Eggs can withstand cold storage (7° to 9 °C.) for 10 days before survival is impaired. Thereafter, mortality increases logarithmically until the 100 percentile is reached at about 43 days.

Studies on the Behavior and Development of Enoclerus lecontei (Wolcott), a Predator of the Western Pine Beetle

Observations on the life cycle and habits of Enoclerus lecontei were made in the laboratory and field. The eggs passed through distinctive color changes during their development; these color changes were used to determine their age. The three larval instars were separated on the basis of head capsule width. Larval size varied according to the amount of food consumed. All larvae were orange-red in color, except the third instar which altered to purple 4 to 6 days after moulting. The duration of the respective stadia were first, 8 to 15 days; second, 5 to 8 days; third, 19 to 35 days. At least one mature prey-larva was necessary for development in each instar but up to seven were consumed. The third instar fed for only 4 to 11 days, the remaining time was spent in a highly mobile, non-feeding stage. The pupal stage lasted 9 to 11 days. Adults lived 36 to 114 days and consumed from 44 to 158 bark beetle adults. The sex ratio was 1:1. The mating habits, oviposition behavior and feeding behavior are described.