Tamera M. Lewis

Diversity and Phenology of Predatory Arthropods Overwintering in Cardboard Bands Placed in Pear and Apple Orchards of Central Washington State

Abstract Overwintering shelters composed of cardboard bands were placed on pear and apple trees located in central Washington state to monitor overwintering by predatory arthropods and by two pest taxa. A subset of bands was sampled at regular intervals between late summer and mid-December to determine when taxa began to enter bands. The remaining bands were left undisturbed until collection in mid-December to determine the numbers and types of arthropods overwintering on tree trunks in these orchards. More than 8,000 predatory arthropods were collected from bands left undisturbed until mid-December, dominated numerically by Acari (Phytoseiidae) [Galendromus occidentalis (Nesbitt), Typhlodromus spp.], Araneae, and Neuroptera (Hemerobiidae, Chrysopidae). Predatory mite numbers were higher in bands placed in apple orchards than bands placed in pear orchards. The Araneae were particularly diverse, including >3,000 spiders representing nine families. Less abundant were Heteroptera, including a mirid [Deraeocoris brevis (Uhler)] and three species of Anthocoridae [Anthocoris spp., Orius tristicolor (White)]. Coleoptera included Coccinellidae, dominated by Stethorus picipes Casey, and unidentified Staphylinidae and Carabidae. The bands that were collected at regular intervals to monitor phenology provided >15,000 predatory arthropods, dominated numerically by spiders, Dermaptera [Forficula auricularia (F.)], lacewings, and predatory mites. Some well-defined phenological patterns were apparent for some taxa. Brown lacewing adults (Hemerobius) began appearing in bands in late October, coinciding with leaf fall in orchards. Cocooned larvae of green lacewings (Chrysopa nigricornis Burmeister), conversely, were most abundant in bands in September, which was well before leaf fall. Predatory mites began to appear in bands in late September before onset of leaf fall. Patterns for predatory Heteroptera were less clear, but results showed that D. brevis and O. tristicolor were active in the orchards well into the period of leaf fall. Two pest taxa, spider mites (Tetranychus spp.) and pear psylla [Cacopsylla pyricola (Foerster)], were also monitored. Spider mites entered bands beginning in September and finished movement at the beginning of leaf fall, similar to patterns shown by Phytoseiidae. Pear psylla moved into bands very late in the season (November and December). Our results suggest that postharvest applications of chemicals, as made by some growers, would occur before most predatory taxa have entered overwintering quarters.

Seasonal distribution of Anthocoris spp. and Deraeocoris brevis (Heteroptera : Anthocoridae, Miridae) in orchard and non-orchard habitats of central Washington

Abstract Occurrence of Anthocoris tomentosus Péricart, A. antevolens White, A. whitei Reuter, and Deraeocoris brevis (Uhler) in non-orchard habitats is described for areas adjacent to the pear growing regions of Yakima, WA. The four species were found on a number of tree and shrub species, especially willow, cottonwood, oak, alder, aspen, poplar, and bitterbrush. The four predators differed in degree of specialization. A. whitei was found almost exclusively on antelope bitterbrush (Purshia tridentata Pursh), apparently in close association with an unidentified psyllid. The other two anthocorids were more generalized, but differed in occurrence on some tree species. Adult and immature A. antevolens were common on oak, cottonwood, and poplar. Conversely, A. tomentosus was comparatively uncommon on these species, but was more abundant than A. antevolens on the neighboring willows; immatures of A. tomentosus were never recovered from oak. Adult and immature D. brevis were collected from several species not shown to support populations of Anthocoris spp., suggesting that the mirid is more of a generalist than the anthocorids. Anthocoris spp. were rare in apple orchards, whereas D. brevis was common there. A. tomentosus and A. antevolens showed distinct seasonal changes in plant use. Both species congregated on willow catkins beginning in March, but began to appear on summer hosts (oak, cottonwood, alder, aspen, poplar) in May and June. Some of the movement from willow may have been a result of the disappearance of a univoltine psyllid from this host plant. Traps composed of corrugated cardboard were placed at different sites to collect overwintering predators. A. antevolens and D. brevis were more broadly distributed among plant species than A. tomentosus or A. whitei (the latter restricted to pear and bitterbrush). A. antevolens was very abundant in traps collected from poplar and cottonwood, apparently because both tree species are important sources of late-summer prey for this predator. Other miscellaneous Anthocoridae and Deraeocoris spp. were collected while sampling, and lists of these species are provided. Orius tristicolor (White) was common at several sites, and was easily the most abundant anthocorid in overwintering traps at one intensively sampled orchard. This species was particularly abundant in traps placed in peach trees. Overwintering sex ratios of D. brevis, Anthocoris spp., and O. tristicolor were moderately to strongly female-biased.

Effects of fenoxycarb on ovarian development, spring fecundity and longevity in winterform pear psylla

The insect growth regulator fenoxycarb prompts ovarian development in diapausing winterform pear psylla, Cacopsylla pyricola (Förster) (Homoptera: Psyllidae). We applied fenoxycarb to caged psylla in September, November, and December to test whether premature ovarian development reduced overwintering survival, spring fecundity, or spring longevity. Fenoxycarb prompted ovarian development in all treated psylla, with the largest effects occurring in the September‐treated insects. Recovery of live psylla in spring was 46–95% in treated insects and 72–92% in controls; overwintered insects from the fenoxycarb treatments survived field temperatures below −20°C despite having had mature ovaries. Fecundity and longevity of psylla were the same in treated and untreated insects, indicating that overwintering with mature ovaries did not cause reduced spring egglaying capacity. Several treated insects each deposited over 1900 eggs and survived more than 120 days. Due to their more advanced development, treated insects had higher oviposition rates than controls during the first 5 days after removal from the field. The largest impact on spring fitness was due to the effects of fenoxycarb on egg hatch. Eggs deposited on clean foliage by September‐treated females were less likely to hatch than eggs deposited by controls, suggesting that fenoxycarb affected developing eggs within the female. Prospects for using fenoxycarb in fall to control pear psylla appear to be limited.

Size and Shape Differences in Genitalia of Males from Sympatric and Reproductively Isolated Populations of Anthocoris antevolens White (Heteroptera: Anthocoridae) in the Yakima Valley, Washington

Abstract Anthocoris antevolens White (Heteroptera: Anthocoridae) is a widespread predatory bug in North America commonly associated with deciduous trees and shrubs. Unpublished observations showed that there is considerable geographic variation in male genitalia in this species and that the variation may lead to reproductive isolation among geographically separated populations. We show that male bugs from two sympatric populations in the Yakima Valley, Washington, one occurring on oak (Quercus garryana Douglas) and the other collected from willow (Salix sp.), differed in size and shape of the phallus and clasper. Mating trials showed that males from the oak source successfully inseminated females from the oak source in 75% of pairings; insemination success for males from the willow source paired with females from the willow source was somewhat lower at 62%. In nonlike crosses (oak × willow, willow × oak), males failed to inseminate the female in 100% of pairings, despite vigorous mating attempts by the males. Copulation duration was independent of population source. However, males from the willow source initiated copulation attempts significantly sooner in the assay than males from the oak source, irrespective of female source. We interrupted copulating pairs by freezing them with liquid nitrogen and showed that males in nonlike crosses generally had failed to fully inflate the phallus in the female. Results support statements made elsewhere that A. antevolens is actually composed of an unknown number of reproductively isolated cryptic species.

Mating preference, mating propensity, and reproductive traits in Anthocoris nemoralis (Heteroptera : Anthocoridae) : A comparison of California and United Kingdom populations

Abstract The predatory bug Anthocoris nemoralis (F.) is a common species native to Europe that has become established in several areas of North America. The objectives of this study were to determine whether North American and European insects differed in aspects of mating activity and reproduction. We compared mating preferences, mating propensities, and some life history traits between a European (England) and North American (San Francisco Bay area) population of A. nemoralis; the North American population colonized the source locale apparently between 10 and 30 yr ago. In no-choice and choice assays, the insects showed no preference for mating with insects from the same source population. Both types of assays indicated that insects from the two sources differed in mating propensities: UK females were less likely to mate during a 30-min assay than females from California (irrespective of male source); and California males were less likely to mate than males from the UK (regardless of female source). More than 80% of mated females matured ovaries from all population crosses. Copulation duration was shorter in pairings involving California males (13.8 min) than matings involving UK males (16.9 min). The preoviposition period averaged ≈3 d for females from both populations. Insects of both sexes from both populations were able to mate within 24–48 h of adult eclosion. Younger males of both populations copulated longer and were less likely to prompt ovarian maturation in the female than older males. Several characteristics of A. nemoralis, including its generalist feeding habits, rapid maturation, short preoviposition period, and low levels of mating discrimination may help explain why this species has been successful in colonizing new geographic areas.

Morphological and Genetic Divergence in Three Populations of Anthocoris antevolens (Hemiptera: Heteroptera: Anthocoridae)

Abstract Anthocoris antevolens White (Hemiptera: Heteroptera: Anthocoridae) is a widespread predatory bug in North America that exhibits substantial geographic variation in coloration, body measurements, size and shape of the male genitalia, pubescence, and sexual behavior. Earlier behavioral studies with three populations (including two populations that are sympatric in central Washington) showed that there was limited or no successful mating between insects from nonlike populations, despite vigorous mating attempts by males. The current study shows that males from those three populations diverge also in size and shape of claspers, length of the phallus, body measurements, and pubescence. Divergence extends to the two sympatric populations. Analysis of mitochondrial DNA shows that phenotypic divergence is associated with genetic divergence. Results reported here, in combination with the earlier published mating trials, support statements made elsewhere by us that A. antevolens is actually a complex of an unknown number of externally similar species.

Differences in Mating Behavior Among Three Populations of Anthocoris antevolens (Heteroptera: Anthocoridae): A Comparison of Intra- and Interpopulation Crosses

Abstract Mating behavior was compared among three populations of Anthocoris antevolens White (Heteroptera: Anthocoridae). Two of the three populations are sympatric in the Yakima Valley, Washington, and are known to differ in length of the setae on the hemelytra and in characteristics of the male’s genitalia. The third population occurred 120 km west of the Yakima populations. All possible inter- and intrapopulation crosses were studied. Males attempted to mate females in all crosses and were as rapid in initiating mating attempts in interpopulation crosses as in intrapopulation crosses. Mating success, defined to be insemination of the female, varied between 64 and 92% in intrapopulation crosses, but only between 0 and 21% in interpopulation crosses. The crosses between the two sympatric populations never resulted in insemination. Females in all crosses resisted mating attempts by males. Resistance behavior included hunching of the abdomen to prevent insertion of the clasper by the male, use of a hind leg to block male attempts to insert the clasper, and attempts to dislodge the male. For two of the populations, female resistance increased when paired with a male from a different population than when paired with a male from her population; females from the third population showed similar levels of resistance in interpopulation and intrapopulation crosses. Our results support the idea that A. antevolens is actually composed of an unknown number of reproductively isolated cryptic species.

Morphology, Genetics, and Male Mating Success Compared Between Anthocoris musculus and A. antevolens (Hemiptera: Heteroptera: Anthocoridae)

Abstract The predatory true bugs Anthocoris antevolens White and A. musculus (Say) (Hemiptera: Heteroptera: Anthocoridae) are geographically widespread species in North America having broadly overlapping ranges. The two species are similar in coloration, size, host-plant use, and general appearance of the male genitalia. They are separated in keys by characteristics of the pubescence on the hemelytra: A. antevolens, pubescence long and dense; A. musculus, pubescence short and sparse. However, the extensive variability in this trait, in combination with similarities in other traits, has led to questions about whether A. antevolens and A. musculus are actually distinct species. We compared behavioral, morphological, and molecular genetic traits among specimens collected from four geographic regions, whose appearance would identify them as A. musculus (from three populations: Maine, Michigan, Montana) or as A. antevolens (from one population: central Washington). We included for comparison results for three populations of A. antevolens shown in earlier publications to differ in behavior, morphology, and mitochondrial DNA. Our results showed that identifications made using pubescence traits often failed to parallel variation in other characteristics, notably appearance of the male genitalia, mating success, and DNA sequences. In sum, our results indicate that variation among populations of A. antevolens in morphological, behavioral, and genetic traits may often exceed differences in those same traits between A. musculus and A. antevolens, if identifications are made using available keys.

Tethered flight activity of pear psylla, Cacopsylla pyricola: seasonal, host, and morphotypic effects

Pear psylla, Cacopsylla pyricola Förster (Homoptera: Psyllidae), was flown in the laboratory to test hypotheses suggested by field observations. Flight durations of the same insects flown on two different days were highly correlated, suggesting that there were biological differences among insects in flight tendencies. Flight durations were similar between summerform and winterform morphotypes. Flight frequencies and durations increased between September and November collections of winterforms, results that are consistent with field observations. Long‐duration (60+ min) flights were three to four times as frequent in winterforms restricted to senescing pear foliage compared to insects provided access to pear seedlings. Winterforms collected during the fall flight period from a pear orchard and an adjacent apple orchard (an overwintering habitat) showed similar flight durations. There was no correlation between flight durations and any of five body and wing measurements; body size of winterforms increased between September and November. It has been proposed elsewhere that much of the fall movement into adjacent non‐pear habitats by winterforms is due to short duration non‐migratory flights rather than to a true migratory flight. The lack of differences between apple‐ and pear‐collected winterforms may be consistent with this hypothesis.

Interplant movement by pear psylla (Homoptera: Psyllidae): Effects of sex ratio and reproductive status

Sticky trap catch of pear psylla,Cacopsylla pyricola Foerster, is male biased during the reproductive generations, but not the diapausing generation. In cage studies, we monitored movement by male and female pear psylla between host plants, and tested whether reproductive and diapausing psylla exhibit similar rates of movement. We also experimentally varied sex ratio to determine whether sex ratio affected movement. Male-biased sex ratios prompted increased movement off of the original host by male psylla of the reproductive generations; no such effect was noted for diapausing insects. We interpret these results to indicate that male movements increased under male-biased conditions due to mate-searching activities. There was also evidence in two experiments that severely male-biased sex ratios prompted movement off of the original host plant by reproductive females; this effect may have been due to harassment of ovipositing females by males.