James R. Nechols

Use of the random amplified polymorphic DNA polymerase chain reaction (RAPD-PCR) to detect DNA polymorphisms in aphids (Homoptera: Aphididae)

We have used a new technique to identify discrete genetic markers in aphids, a family in which biochemical and morphological genetic polymorphisms are rare. The new technique uses the polymerase chain reaction (PCR) to amplify random regions of aphid genomes (random amplified polymorphic DNA) and has been termed RAPD-PCR. We demonstrate the use of the technique in revealing genetic variation in four aphid species, the greenbug ( Schizaphis graminum (Rondani)), the Russian wheat aphid ( Diuraphis noxia (Mordvilko)), the pea aphid ( Acyrthosiphon pisum (Harris)), and the brown ambrosia aphid ( Uroleucon ambrosiae (Thomas)). In contrast with allozyme surveys, RAPD-PCR revealed large amounts of genetic variation among individuals in each of these species. Variation was detected among biotypes, populations, colour morphs and even individuals on a single plant. We also explored the utility of RAPD-PCR in the detection and identification within aphid bodies of two endoparasitic wasps, Diaeretiella rapae (McIntosh) and Lysiphlebus testaceipes (Cresson). The use of RAPD-PCR in species diagnostics, parasitoid detection, and population studies is discussed.

Thermal Requirements for Development in Chrysopa Oculata: A Geographically Stable Trait

Chrysopa oculata from five widespread localities (southern Canada to montane Mexico), exhibited remarkable similarities in their thermal requirements for nondiapause development. Lower thermal thresholds (t) varied by only 1.2°C., and the degree—days required for total preimaginal development (K) differed among the populations by °85°d. Despite the similarities among populations, the results suggest that the thermal requirements for development are genetically variable. However, two factors may limit the geographical expression of this variation: (1) the multivoltine life cycle could result in seasonal oscillations in the magnitude and projection of directional selection on the nondiapause thermal responses, and/or (2) the thermal thresholds for development and the rates of development above the thresholds may be functionally correlated and constrained in their evolution. Males from all populations emerged slightly but consistently earlier than females. Temperature did not affect sex or survival, other than at 15.6.° where mortality was significantly increased. Among the five populations, only one large difference occurred in the thermal responses; under low temperatures, a relatively high proportion of the two northern populations entered diapause. The differences in diapause induction resulted from the differential effect of temperature on the critical photoperiod for diapause induction, rather than on the developmental rates.

Two Genes Control Seasonal Isolation in Sibling Species

Interspecific hybridization tests between Chrysopa carnea and Chrysopa downesi show that single allele differences at two unlinked autosomal loci cause large differences in photoperiodic responses. These differences produce asynchronous seasonal reproductive cycles, thus forming an effective temporal reproductive barrier between the two sympatric species. The results subserve the development of a genetic model for allochronic speciation.

Efficacy of Beauveria bassiana for Red Flour Beetle When Applied with Plant Essential Oils or in Mineral Oil and Organosilicone Carriers

Abstract The carriers mineral oil and Silwet L-77 and the botanical insecticides Neemix 4.5 and Hexacide were evaluated for their impacts on the efficacy of Beauveria bassiana (Balsamo) Vuillemin conidia against red flour beetle, Tribolium castaneum (Herbst), larvae. The dosages of liquid treatments were quantified by both conidia concentration in the spray volume and conidia deposition on the target surface. The latter approach allowed comparison with dry, unformulated conidia. The median lethal concentrations of B. bassiana in 0.05% Silwet L-77 solution or without a carrier were approximately double that for conidia in mineral oil. Carriers had highly significant effects on the efficacy of B. bassiana. The lower efficacy of conidia in aqueous Silwet L-77 may have been the result of conidia loss from the larval surface because of the siloxane’s spreading properties. Neemix 4.5 (4.5% azadirachtin) delayed pupation and did not reduce the germination rate of B. bassiana conidia, but it significantly reduced T. castaneum mortality at two of four tested fungus doses. Hexacide (5% rosemary oil) caused significant mortality when applied without B. bassiana, but it did not affect pupation, the germination rate of conidia, or T. castaneum mortality when used in combination with the fungus.

Geographical variability in ecophysiological traits controlling dormancy in Chrysopa oculata (Neuroptera: Chrysopidae)

Abstract Dormancy in Chrysopa oculata, a multivoltine species, is controlled by reponses to photoperiod and temperature. Variation in both the critical photoperiod for diapause induction and the duration of diapause is positively related to the latitudianl origin of the population. The incidence of photoperiodically induced diapause also varies geographically; at 24°C the southern-most population is more variable for diapause induction than the northern populations. By contrast, there is little interpopulation variation in thermally determined rates of post-diapause development. The results suggest that the lower threshold for development and the thermal requirements above the threshold may be functionally correlated.

Movement Behavior of Red Flour Beetle: Response to Habitat Cues and Patch Boundaries

ABSTRACT Movement behavior determines the success or failure of insects in finding important resources such as food, mates, reproductive sites, and shelter. We examined the response of female red flour beetles (Tribolium castaneum Herbst; Coleoptera; Tenebrionidae) to habitat cues by quantifying the number of individuals that located a patch (either with or without flour) in response to the distance released from the patch, air movement over the arena, and food-deprivation status. We also investigated how patch characteristics, such as resource amount and presence of cover, influenced time taken to find a flour patch, the frequency of entering or leaving, and residence time within the patch. Although the proportion of beetles successfully locating the patch decreased as a function of release distance, the probability that beetles reached the patch was ultimately unaffected by whether flour was present or not, suggesting that search behavior in red flour beetles may exhibit a simple distance-decay function. Significantly more beetles reached the patch when they had not been food deprived and air was flowing over the arena, which indicates that walking beetles may orient to airflow, exhibiting anemotaxis. Results of the second experiment showed that, on first encounter, fewer beetles entered patches with a greater amount of flour; but once they had entered, they left them less frequently than patches with less resource. Beetles entered covered patches more quickly than uncovered patches irrespective of resource amount, which indicates that shelter is perhaps more important to red flour beetles than resource levels in determining whether to enter patches.

A new role for temperature in insect dormancy: cold maintains diapause in temperate zone Diptera.

In early autumn, high temperatures terminate diapause in the alfalfa blotch leafminer Agromyza frontella; low temperatures maintain diapause. These responses subserve a thermally malleable dormancy and allow flexibility in the annual number of generations. The view that favorable conditions cannot reverse the course of diapause are contradicted by the data on A. frontella. A better understanding to life history studies and phenological models in insect pest management.

Mating Behavior of Cephalonomia tarsalis (Ashmead) (Hymenoptera: Bethylidae) and the Effect of Female Mating Frequency on Offspring Production

The courtship behavior of Cephalonomia tarsalis, a solitary semiectoparasitoid of Oryzaephilus surinamensis, was investigated in the laboratory. Courtship behavior includes a series of stereotypic movements. Males play the most active role, executing the majority of courtship action, and females respond with relatively limited observable behaviors. Males typically keep antennae still during encounters with females prior to mounting, which may be correlated with recognition of the females sexual status. After mounting, males display a series of movements on females, such as antennae touching females antennae, antennae or mouth touching females head or thorax, and walking around on female, which may serve to stimulate females towards increased receptivity. Females signal receptivity by assuming a stereotypical posture of remaining stationary, with head down, and antennae still in front of the body. The male then inserts his aedeagus and the pair copulates. After an average of 40.4 s of copulation, females signal the end of copulation by waving the antennae and moving away from the copulation site. Males continue copulating for a short time after females start moving but dismount soon thereafter. After dismounting, the two wasps move away from each other immediately, and they typically begin grooming. Neither males nor females exhibit mating preference based on mates mating status in both choice and no-choice tests. The male is polygynous and the mated female can mate multiple times within the first 3 days after starting oviposition. However, female mating frequency does not affect the production of female progeny.

Efficacy of methoprene applied at different temperatures and rates on surface substrates to control eggs and fifth instars of Plodia interpunctella.

ABSTRACT A series of studies was conducted to determine the effects of temperature on toxicity of the insect growth regulator methoprene to eggs and larvae of Plodia interpunctella (Hübner), the Indianmeal moth. When methoprene was applied to Kraft paper at the rate of 0.0003 mg of active ingredient [(AI)]/cm2, there was little direct toxicity against eggs of P. interpunctella, and temperature did not affect insecticide efficacy. Similarly, exposure of eggs on a paperboard surface treated with different rates of methoprene resulted in delayed adult emergence but not a reduction in adult emergence. However, wandering-phase larvae of P. interpuctella were susceptible to methoprene, and exposure of larvae for 0.5, 1, and 2 h on different packaging materials resulted in reduced adult emergence. There was variation in emergence depending on the specific surface, but temperature had no effect on resulting adult emergence from exposed larvae. A partial budget analysis described treatment costs and reduction of risks associated with control of eggs and larvae of P. interpunctella. Results indicate methoprene could be used in management programs to control larvae of P. interpunctella, but eggs may be able to compensate for exposure to methoprene residues on treated surfaces.

Within-Plant Distribution of Twospotted Spider Mites (Acari: Tetranychidae) on Impatiens: Development of a Presence–Absence Sampling Plan

Abstract The twospotted spider mite, Tetranychus urticae Koch, is an important pest of impatiens, a floricultural crop of increasing economic importance in the United States. The large amount of foliage on individual impatiens plants, the small size of mites, and their ability to quickly build high populations make a reliable sampling method essential when developing a pest management program. In our study, we were particularly interested in using spider mite counts as a basis for releasing biological control agents. The within-plant distribution of mites was established in greenhouse experiments and these data were used to identify the sampling unit. Leaves were divided into three zones according to location on the plant: inner, intermediate, and other. On average, 40, 33, and 27% of the leaves belonged to the inner, intermediate, and other leaf zones, respectively. However, because 60% of the mites consistently were found on the intermediate leaves, intermediate leaves were chosen as the sampling unit. These results lead to the development of a presence–absence sampling method for T. urticae by using Taylor coefficients generic for this pest. The accuracy of this method was verified against an independent data set. By determining numerical or binomial sample sizes for consistently estimating twospotted spider mite populations, growers will now be able to determine the number of predatory mites that should be released to control twospotted spider mites on impatiens.