Retracing the routes of invasions and determining the origins of invading species is often critical in understanding biological invasions. The Western conifer seed bug, Leptoglossus occidentalis, an insect native of western North America, was first accidentally introduced to eastern North America and then to Europe. The colonization of the entire European continent occurred in ca. 10-15 years, probably promoted by independent introductions in different parts of Europe. A multi-marker approach (mtDNA and microsatellites) combined with approximate Bayesian computation analyses was used to track the origin of European populations and to determine whether this rapid invasion was caused by multiple introductions. Our results show that at least two independent introductions of L. occidentalis have occurred in Europe. Moreover, the analyses showed a stronger genetic similarity of European invasive populations with the eastern North American populations than with those of the native range, suggesting that invasive North American population acted as a bridgehead for European invasion. The results also revealed that natural dispersal as well as human-mediated transportations as hitchhikers probably enhanced the rapid spread of this invasive pest across Europe. This study illustrates the complexity of a rapid invasion and confirms that bridgehead and multiple introductions have serious implications for the success of invasion.

Stone cells are a physical defence of conifers against stem feeding insects such as weevils and bark beetles. In Sitka spruce, abundance of stone cells in the cortex of apical shoot tips is associated with resistance to white pine weevil. However, the mode of action by which stone cells interfere with growth and development of weevil larvae is unknown. We developed a bioassay system for testing potential effects of stone cells, which were isolated from resistant trees, on weevil larvae. Bioassays using artificial diet and controlled amounts of stone cells focused on physical defence. We evaluated the effects of stone cells on establishment of neonate larvae, mandible wear and changes in relative growth rates of third instar larvae. Establishment of neonates and relative growth rates of third instars were significantly reduced by stone cells. Stone cells appeared to be indigestible by weevil larvae. Our results suggest that stone cells affect weevil establishment and development by forming a physical feeding barrier against neonate larvae at the site of oviposition, and by reducing access to nutrients in the cortex of resistant trees, which contain an abundance of stone cells in place of a more nutrient rich tissue in susceptible trees.

We report that a chemical stimulus from a herbivore, a galling insect, changes plant morphology and physiology to benefit the herbivore. Previous studies could not determine whether insect galls are induced by mechanical or chemical stimuli because feeding and oviposition both occurred at the site of gall formation. We report that the mouthparts of a spruce‐galling insect, Adelges cooleyi, were inserted in stem phloem cells far from induced galls, that tissues between mouthparts and galls appeared normal, and that the ability to initiate galls was inversely correlated with distance from buds (potential gall sites). Thus the effects of chemical stimuli were unambiguously separated from any mechanical influence of probing stylets or ovipositors. Our results strongly suggest that galls were induced by a chemical stimulus transported to buds via vascular tissue and that its efficacy was dose‐dependent.

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The sex pheromone of the fir coneworm moth consists of a blend of (3Z,6Z,9Z,12Z,15Z)-pentacosapentaene and (9Z, 11E)-tetradecadienyl acetate. Analogous blends of polyunsaturated, long-chain hydrocarbons with much shorter chain aldehydes or alcohols recently have been discovered in three other moth species in the superfamily Pyraloidea. These combinations of components from two distinct structural classes may represent an important and widespread new pheromone blend motif within the Lepidoptera.

Croft. B.A., Messing, R.H., Dunley. J.E. and Strong, W.B. 1993. Effects of humidity on eggs and immatures of Neoseiutus fatlacis, Amblyseius andersoni, Metaseiutus occidentalis and Typhh~-dromus pyri (Phytoseiidae): implications for biological control on apple, caneberry, strawberry' and hop. Exp. Appl. Acarol., 17: 451--459.The lethal humidity (LHso) responses at 20°C of eggs of two strains ofNeoseiulusfallacis (Garman) were 71.6 and 69.7%; of three strains ofAmblyseius andersoni (Chant) were 62.9, 62.0 and 62.4% and of one strain each of T~phlodromus pyri Scheuten and Metaseialus occidentalis Nesbitt were 55.0 and 28.4%, respectively. Eggs of three genetically distinct strains ofA. amtersoni from Oregon, the Netherlands and Italy did not respond differently from one another nor did eggs of freely hybridizing N. fallacis from Michigan and Oregon. Mortality of larvae through development to early protonymphs at 50% RH, 20°C. was 91.9.82.3.46.2 and 31.0% for fed mites and 98.1, 83.2.67.0 and 89.7% for unfed mites of Oregon strains of N. fidlacis, A. andersoni, T. pyri and M. occidentalis, repectively. Fed larvae-protonymphs ofM. occidentalis and T. pyri were more tolerant of low humidity than fed larvae-protonymphs ofN. fallacis and A. andersoni. Mortality was less for fed than unfcd larvae-protonymphs of M. occidentalis and/i pyri, but there were no differences tbr A. andersoni and zh: fallacis. Levels of feeding by predator larvae on T. urticae and cannibalism by phytoseiid protonymphs contributed to species differences. Responses to humidity are discussed in relation to geographic and host plant distributions and biological control by single or mixed species populations of phytoseiids.

The major components of the sex pheromone of Dioryctria abietivorella (Groté) (Lepidoptera: Pyralidae) were recently identified as (9 Z ,11 E )-tetradecadien-1-yl acetate (9 Z ,11 E -14:Ac) and a polyunsaturated, long-chain hydrocarbon (3 Z ,6 Z ,9 Z ,12 Z ,15 Z )-pentacosapentaene (C25 pentaene). The optimal ratio of these components and the role of potential minor components were not fully determined in the initial short report on the pheromone's identification. We tested different ratios of the two major components loaded into grey halobutyl rubber septum dispensers, placed in sticky traps deployed in conifer breeding arboreta. The optimal ratio of the two components was 200 µ g 9 Z ,11 E -14:Ac to 2000 µ g C25 pentaene. ( Z )-9-Tetradecen-1-yl acetate, which had been identified previously in female pheromone gland extracts, and five other potential minor pheromone components, were tested individually as additions to the optimized two-component lure blend. None of the ternary blends were more attractive than the optimized two-component blend, at the ratios tested. Two lure adjuvants, a UV stabilizer (Sumisorb 300) and the antioxidant butylated hydroxytoluene, added individually or together, did not affect the attractiveness of the optimized lure blend. The Pherotech diamond sticky trap baited with the optimized lure blend was the most effective trap design among eight types of sticky trap and a bucket style trap that were tested. Traps baited with synthetic lures were as attractive as traps baited with virgin female moths. The optimized two-component lure blend in the Pherotech diamond trap is recommended for monitoring fir coneworm infestations. The availability of an effective synthetic pheromone opens the possibility for control tactics using mating disruption or attract-and-kill techniques.

Low seed set is a serious problem in seed orchards of lodgepole pine (Pinus contorta var. latifolia Engelmann) in the southern interior of British Columbia. We tested the hypothesis that Leptoglossus occidentalis Heidemann is responsible for the low seed set. Cones enclosed in insect exclusion bags as part of a pollination experiment produced significantly more filled seeds per cone than cones that were not bagged. In a separate bagging experiment, cones that were enclosed with a L. occidentalis female and her progeny produced only about one filled seed per cone, compared with about 28 seeds in bagged control cones. Changes in microclimate associated with the use of bags did not appear to be responsible for the observed increase in seed set in bagged cones. Leptoglossus occidentalis was also excluded from trees using the insecticide fenvalerate. Cones on fenvalerate-treated trees produced > 11 filled seeds per cone, whereas water-treated (control) cones produced < 1.7 filled seeds. These data suggest that L. occidentalis should be considered a serious pest in lodgepole pine seed orchards.