The spatio-temporal distribution of cotton plants, Gossypium hirsutum L., infested with Aphis gossypii (Glover) winged adults, is described in a plot located in Bangui, Central African Republic. Each cotton plant growing in the plot was examined visually for a short period of time to ascertain the presence or absence of A. gossypii and to construct weekly infestation maps. Tests of autocorrelation and dispersion were carried out at different spatial scales by means of Monte Carlo procedures on embedded counting grids. Edge effect tests were also carried out. The statistical analyses show significant overdispersion of the infested plants and positive spatial autocorrelation. Positive temporal autocorrelation and significant edge effect are detected intermittently throughout the season.

New Brunswick experienced its first recorded outbreak of hemlock looper, Lambdina fiscellaria fiscellaria (Guenée) (Lepidoptera: Geometridae), in 1989 (Magasi1990). Since 1993, populations have remained at endemic levels. From 1989 to 1994, when annual egg surveys were conducted (from October to April) on balsam fir, Abies balsamea (Linnaeus) Miller (Pinaceae) to forecast the next years' population for planning foliage protection programs, the egg parasitoids Trichogramma minutum Riley (Hymenoptera: Trichogrammatidae) (Hartling et al. 1991) and Telenomus near alsophilae Viereck (Hymenoptera: Scelionidae) were frequently reared from overwintering looper eggs. We believe two factors can cause an underestimation of egg parasitism rates by Telenomus near alsophilae: (i) eggs parasitized by Telenomus near alsophilae can be difficult to identify, and need to be reared to detect the black shading on the chorion which ranges from a mere dark spot to some gradation of black over the entire surface; and (ii) additional parasitism by this parasitoid might occur in spring. Our estimates of egg parasitism rates were as high as 23% (n = 93) from spring-collected looper eggs incorrectly classified as viable until incubated in the laboratory. We describe part of an experiment that confirms spring parasitism by this species, and illustrate the implications to operational looper control operations.

Survival of the spruce beetle, Dendroctonus rufipennis Kirby, from egg to adult, proportion of 1- and 2-year-cycle adults, and egg and egg gallery production per attack were investigated over five generations in stumps and windfall in central British Columbia. Densities of attacks, egg gallery lengths, and brood in various stages of development were obtained by repeated sampling throughout the life cycle. Spruce beetle populations remained at suboutbreak levels throughout the duration of the study. There were generally no differences by area, host type, or infestation year in any of the measured variables. The mean numbers (±SD) of eggs per attack and eggs per centimetre of egg gallery were 80.8 (54.3) and 5.4 (4.6), respectively. Brood survival from egg to adult averaged 6.8%. The lowest and highest survival from egg to adult occurred in the same years as when the lowest and highest percentage of 1-year-cycle adults were produced, respectively. On average, 51.8% of the beetles in stumps and 19.1% of beetles in windfall developed on a 1-year cycle.

We examined the factors that might influence ovary development in worker honey bees, Apis mellifera L. Queenless workers at different ages (≤ 12 h, and 4, 8, and 21 d) were tested in cages for ovarian development. Newly emerged, 4- and 8-d-old, and 21-d-old workers had medium-, large-, and small-sized ovaries, respectively, suggesting that of the worker ages tested only 4- and 8-d-old workers are likely to become egg layers in a queenless colony. Also, we compared ovarian development of newly emerged workers that were caged for 14 d and allowed to consume either pollen or royal jelly to that of another group of workers similarly caged but screened so that they could only obtain food via trophallaxis from young bees. Ovaries of newly emerged workers that received food from young bees were as well developed as those of newly emerged workers allowed to take pollen or royal jelly directly. Screened workers also had lower but still elevated vitellogenin levels compared with bees having direct access to food. These results indicate that nurse-age bees functioning as pollen-digesting units affect the ovarian development of other workers and to a lesser extent vitellogenesis via food exchange. We compared the influence of group sizes of 25, 125, and 600 bees per cage on ovarian development for 14 d. The two groups of 25 and 125 bees had similar mean ovary scores, and higher scores than a group of 600 bees. Our findings suggest that nurse-age bees could play an important role in mediating worker fertility via trophallaxis, possibly by differentiating worker dominance status, and generally only young workers become fertile when a queen is lost in a colony. Vitellogenin is a more sensitive parameter to measure bee fertility, and might be a useful tool to further explore ovary development and egg laying in worker social insects. We recommend measuring haemolymph vitellogenin titres and (or) oocyte length of workers in a group of 25 bees per cage, supplied with 50% royal jelly in honey as a standard method to assess honey bee worker fertility in future experiments.

Pitfall and screen traps were used around potato Solanum tuberosum L. (Solanaceae) plots to detect directional patterns of prediapause (two seasons) and postdiapause (one season) movement in a univoltine population of the Colorado potato beetle, Leptinotarsa decemlineata (Say), from Quebec. Prediapause beetles were sampled for diapause readiness using a feeding–digging test. In 1994, a plot left unprotected from the beetle (moderately defoliated) was monitored. In 1995, movement around a plot left unprotected from the beetle (severely defoliated) was compared to that from a plot protected (only lightly defoliated) by inundative release of the potato beetle predator Perillus bioculatus Say (Hemiptera: Pentatomidae). Movement frequency by postdiapause beetles in spring 1995 was low compared with 1994 prediapause movement, especially on the ground. Low-frequency flying persisted over several weeks of postdiapause beetle oviposition, with only a brief period of directionality. Flight movement by satiated prediapause beetles in August 1994 and 1995 was strongly directional, being oriented toward the closest forest border east of the plots, where sampling confirmed overwintering. In both years, satiated prediapause beetles also emigrated by walking, but mostly from densely populated and defoliated plots. Newly emerged (unsatiated) prediapause beetles emigrated en masse from severely defoliated plants, and did so exclusively by walking. Directional walking contrasted with directional flying in being predominantly oriented south-westward to northwestward, suggesting cueing on the sun position during warm hours of the day.

In randomized complete block experiments using multiple-funnel traps frontalin was only moderately attractive to spruce beetles, Dendroctonus rufipennis Kirby, in northern British Columbia. MCOL (1-methylcyclohex-2-en-1-ol) of any enantiomeric composition significantly enhanced the attraction of both sexes (up to 3.4 and 4.2 times for females and males, respectively) to traps baited with frontalin. The lack of an enantiospecific preference for MCOL aligns beetles in northern British Columbia with those in southeastern British Columbia and northern Alberta, but not with enantiospecific populations in southern British Columbia and Alaska. In tree baits, neither MCOL nor seudenol (3-methylcyclohex-2-en-1-ol) enhanced the efficacy of frontalin. The power of frontalin alone at a release rate of 1.2 mg per 24 h (half the rate in commercial baits) indicates that the currently used operational tree baits could be modified by lowering the dose and eliminating α-pinene.

Lodgepole pines, Pinus contorta var. contorta Engelmann, killed by mountain pine beetle, Dendroctonus ponderosae Hopkins, are often subsequently infested by other scolytid species (Safranyik et al. 1996). Ips pini (Say) breeds in the phloem region of the main bole and larger branches in areas not occupied by mountain pine beetle. Adults emerge in the fall and drop to overwinter in the duff near the bases of their brood trees (Safranyik et al. 1996). Hylurgops porosus (LeConte) infests lodgepole pine (Keen 1952; Bright 1976) stumps or severely weakened trees near the root collar and in large roots (Wood 1982). We examined the pattern of emergence of I. pini and H. porosus from the duff around infested trees to describe changes in density over distance from the trees.

Two colour morphs of Enoplognatha ovata (Clerck), “redimita” and “lineata” the abdomens of which are whitish with two pink stripes and greyish-yellow, respectively, differ in their foraging strategies. When placed in artificial arenas with flowering stems to ascend, we noted that both morphs had a strong tendency to wander over the ground rather than ascend a stem [unlike the crab spider, Misumena vatia Clerck (Araneae: Thomisidae)], but that lineata was significantly more prone to wander than was redimita. Neither morph showed choice for the type of stem or colour of flower. Nevertheless, redimita showed a greater preference for choosing white artificial flowers (discs) atop 30-cm wooden rods than did lineata. We propose that the relative abundances of the two colour morphs in the natural population represents a balanced polymorphism which is maintained in part by polyethism in hunting strategies, with redimita being more fastidious in its selection of cryptic hunting sites in flowers than is lineata, and the latter being more cryptic and more errant on the ground.

Delphastus catalinae (Horn) (Coleoptera: Coccinellidae) was mass reared to support field studies addressing augmentation and colonization for control of Bemisia argentifolii Bellows and Perring (Homoptera: Aleyrodidae) in southern California. Beetles were reared on B. argentifolii infested poinsettia plants grown inside greenhouses located in northern California. Potted plants, reared from rooted cuttings, were cycled through the rearing system over ca. a 12-week period, then discarded. A total of 174 245 adult beetles were harvested over a 20-week period. Each plant averaged 46 adult beetles (range 21–89) over the same period of time. Harvesting strategies were investigated using a computer simulation model based upon published and hypothesized reproduction and survivorship parameters. Results suggest that removal of approximately 50% of adults per week produced a stable and maximum production of beetles. Actual harvest rates were between 40 and 60% of available beetles. The cost of producing each adult was estimated at US$0.22, with the major cost being labor at 86% of the total.

Colorado potato beetle, Leptinotarsa decemlineata (Say), is an important pest of potatoes Solanum tuberosum L. worldwide. To control this insect, commercial growers in North America may increasingly rely on planting transgenic potatoes that express the Bacillus thuringiensis (Berliner) subsp. tenebrionis Cry3A toxin in their foliage (Whalon and Ferro 1998). Because persistence and distribution of the toxin in these plants are maximized (Perlak et al. 1993), there is strong selection pressure towards development of resistance to the Cry3A toxin in beetle populations (Ferro 1993). One strategy proposed to delay development of resistance is to provide spatial refugia of nontransgenic potatoes to support populations of susceptible individuals sufficient to curtail matings between resistant individuals (Whalon and Ferro 1998). Therefore, it is important that susceptible beetles moving into the transgenic crop from refugia can successfully mate with local resistant beetles. Wierenga et al. (1996) reported that adult beetles that fed continuously on transgenic potatoes since eclosion from pupae did not display any reproductive activity, but that successful reproduction was eventually observed if beetles fed on nontransgenic foliage later. Under field conditions, however, it is more likely that susceptible beetles emerging from pupae in refugia will feed on nontransgenic potatoes before, not after, moving onto transgenic plants. We have recently discovered that under such circumstances female beetles remain reproductive, but with significantly reduced fecundity relative to control females continuously fed on nontransgenic foliage (Alyokhin and Ferro 1999). No such data are currently available for male beetles.

Twenty-one species of Coccinellidae were trapped in flight between 0.8 and 14.3 m from 1992 to 1995 in New Brunswick, Canada. Catches were larger at 0.8 m, with a rapidly decreasing capture rate leading, on average, to more than 50% of the catches at or below 3.8 m every year. The capture rate at 14.3 m was lower than at any of the nine other levels. Hippodamia convergeas Guérin-Méneville flights were distributed close to the ground, with more than 50% of catches at 0.8 m, whereas Mulsantina hudsonica Casey flights were similar at all levels. The strong decreasing gradient of flight as a function of height for Coccinellidae (−0.825) was strongly influenced by that of H. convergens (−1.809) and of Coccinella septempunctata L. (−0.921) and Coccinella trifasciata perplexa Mulsant (−0.715). All other species had a slope of less than −0.5. The temporal distribution of flights was species specific, with maximum activity before the end of June for most, but this was not reflected in the frequency of catches for the entire family, which did not differ throughout the season, although they tended to be lower after mid-August. The weekly vertical flight distribution differed from the average distribution pattern only occasionally, probably during periods of long-distance dispersal. These profiles and known catches from a single trap location can be used to estimate dispersal activity at different heights.

The flute-shaped leaves of the pitcher plant Sarracenia purpurea L. are a fluidfilled microhabitat rich in invertebrate diversity (Bradshaw 1983; Heard 1994; Hardwick and Giberson 1996; Harvey and Miller 1996; Miller et al. 1994). They are the obligate larval habitat for Fletcherimyia fletcheri (Aldrich) (Forsyth and Robertson 1975). Most literature reports of F. fletcheri present information only on larval life history and population dynamics (Fish and Hall 1978; Hardwick and Giberson 1996). Forsyth and Robertson (1975) state anecdotally that they observed adults feeding on flowers and other nectar sources within their study area. We believe that our observations represent the first report of adult F. fletcheri roosting within the flower heads of the pitcher plant.

A European gall mite, Aceria malherbae Nuzzaci, was released and established in southern Alberta and Montana as a biological control agent for field bindweed, Convolvulus arvensis L. (Convolvulaceae). Populations of the mite survived for up to 4 years at some sites and caused slight to severe damage to the weed. The establishment of A. malherbae in these areas suggests that it could be established throughout the North American range of field bindweed.

A simple nontoxic technique to mark and reference the white pine weevil Pissodes strobi (Peck) is described. This marking technique was used to track the movement of individuals to the cohort level through time and space in a young white spruce plantation.

Blueberry maggot, Rhagoletis mendax Curran, eggs and larvae infesting highbush ’Bluecrop’ and ’Elizabeth’ blueberries, Vaccinium corymbosum L. (Ericaceae), were treated with 4–1200 Gy of gamma radiation. The treatment reduced the number of immature stages that pupated and the number of adults that emerged from puparia. The lethal dose for 99.9968% mortality (LD 99.9968%) [lower and upper fiducial limits (FL)] estimated by linear regression analysis to stop pupariation was 1486 (1400–1585) Gy, at the 95% confidence level. The LD 99.99968% (lower and upper FL) estimated to stop flies emerging from puparia irradiated as immature stages was 88 (83–93) Gy, at the 95% confidence level as estimated by regression analysis. An estimated 100 762 larvae were killed, with no survivors, by irradiating 853 918 ’Bluecrop’ blueberries in bulk quantities with 71–776 Gy with a commercial irradiator. No flies or parasites emerged from puparia irradiated as larvae with ≥ 71 and > 80 Gy using commercial and research irradiators, respectively. Infestation rate of blueberry maggot larvae in nonirradiated ’Bluecrop’ and ’Elizabeth’ blueberries averaged 11.1 ± 1.2% and 14.3 ± 2.4%, respectively; the range of infestation rate was from 6.3% to 14.8% and 9.8% to 18%, respectively. Parasitism of blueberry maggot larvae by the larval–puparial parasite, Diachasmimorpha (Opius) mellea (Gahan) (Hymenoptera: Braconidae), averaged 10.1 ± 2.4% (range 3–13.3%).

Tracheal mites, Acarapis woodi (Rennie) (Acari: Tarsonemidae), are important parasites of honeybees, Apis mellifera L. (Morse and Flottum 1997). They enter the prothoracic tracheae and feed through the walls on haemolymph. Currently, these mites are controlled by applying 50 g of menthol crystals in a perforated bag per hive when ambient temperatures are 15°C or more. Even then, it takes 2 weeks for the menthol to perfuse the hive (Herbert et al. 1988; Wilson et al. 1990). In cold climates, sublimation of menthol is too slow to be effective in controlling mites, especially in spring and fall when control is most needed (Scott-Dupree and Otis 1992).

Because menthol fumes enter the bees' trachea and kill the mites therein, it may be possible to kill the mites with menthol that is delivered to them via the haemolymph. Therefore, finding if menthol could become systemic when ingested by bees and it could kill tracheal mites by that route, an ingestible menthol medicament for the bees would hold potential for mite control (Kevan and Kevan 1997).

Tree and site characteristics were compared between 19 groups of Douglas-fir, Pseudotsuga menziesii (Mirb.) Franco (Pinaceae), infested by Douglas-fir beetle, Dendroctonus pseudotsugae Hopkins, and 19 uninfested groups to identify individual or combinations of characteristics associated with Douglas-fir beetle attacks. Of the tree characteristics, diameter, height, age, phloem thickness, bark thickness, and a standardized variable consisting of diameter divided by the last 10 years growth rate (DBHTYG) showed significant differences. None of the site characteristics showed significant differences between infested and uninfested areas. Two models, identified through discriminant analysis, placed 84 and 87% of the data in the correct infestation groups. These models included the variables diameter, height, phloem thickness, aspect, and DBHTYG in various combinations. The results were confirmed using a jackknifed cross-validation approach. These variables have potential for use in the development of a biological process model of tree and stand susceptibility to the Douglas-fir beetle.

Natural rubber sleeve stoppers were impregnated with 10 mg of (E)-10-dodecen-1-yl-acetate, the major component of spotted tentiform leafminer, Phyllonorycter blancardella (F.), pheromone. In the laboratory, there was a linear decline in the amount of pheromone remaining on stoppers during 8 weeks of exposure to 10, 15, 20, and 25 °C. At 30 and 35 °C, the relationship was curvilinear and could be described using a second-order polynomial equation. The estimated rate of evaporation ranged from 0.03 mg/day at 10 °C to 0.08 mg/day at 25 °C; the rate of evaporation at 30 and 35 °C varied with the time since first exposure. There was a linear decline in the amount of pheromone remaining on stoppers during 8 weeks of exposure to fluctuating temperature regimes with average temperatures of 10 °C (i.e., 5–15 °C) and 20 °C (i.e., 15–25 °C). At a fluctuating regime with an average temperature of 30 °C (i.e., 25–35 °C), the relationship was curvilinear and could be described using a second-order polynomial equation. The estimated rate of evaporation was 0.02 and 0.09 mg/day at 5–15 and 15–25 °C, respectively; the estimated daily rate of evaporation at 25–35 °C varied with the time since first exposure. In an orchard, the estimated average rate of evaporation of pheromone from stoppers ranged from 0.05 to 0.31 mg/day and did not vary significantly with temperature. During the first 4 weeks of exposure in an orchard, the observed rate of evaporation was up to 4.4-fold greater than the rate predicted using the relationship between evaporation rate and constant temperatures observed in the laboratory. The potential for using natural rubber sleeve stoppers as controlled-release substrates in studies of sex-pheromone-mediated mating disruption of P. blancardella is discussed.

For the last 50 years, populations of the Bruce spanworm, Operophtera bruceata Hulst, and other wingless geometrid species have been sampled using sticky bands placed around host-tree trunks to catch wingless females in search of oviposition sites. This method is tedious and, because of trap saturation by males, may underestimate female populations at moderate to high levels. A standard oviposition trap was developed to sample eggs of the Bruce spanworm and other wingless geometrid species. A small polyurethane foam band placed on a post covered by a Multi-Pher® plate detected low populations and was almost unsaturable during outbreaks. Sub-sampling can be easily done in such situations. Egg density on oviposition traps was higher than female density on sticky bands for both the Bruce spanworm and the fall cankerworm, Alsophila pometaria Harris. This suggests that the oviposition trap might be useful to sample other wingless geometrid species. Operating this system was easy and could involve woodlot owners and companies to reduce the traveling costs necessary to collect samples.