Paul W. Schaefer

Occurrence, Density, and Distribution of Parasitic Fungus Hesperomyces virescens (Laboulbeniales: Laboulbeniaceae) on Multicolored Asian Lady Beetle (Coleoptera: Coccinellidae)

Abstract The coccinellid-specific parasitic fungus Hesperomyces virescens Thaxter was found on the multicolored Asian lady beetle, Harmonia axyridis (Pallas), in fall and winter in Lebanon County, Pennsylvania. Research objectives were 1) to determine the density of H. virescens on field-collected H. axyridis adults held in the laboratory, and 2) to determine H. virescens presence, density, and distribution on H. axyridis adults in the field. In the laboratory, male and female H. axyridis adults hosted >150 H. virescens mature thalli (i.e., fruiting bodies); distributed primarily on the elytra and abdomen. At the overwintering site, H. virescens density per host was often <20 mature thalli, which were distributed primarily on the elytra of both sexes. On average, 52.5 and 57.4% of H. axyridis males and females, respectively, hosted H. virescens mature thalli in late winter (5 March 2003); <14% of either sex hosted mature thalli the following fall (15, 22, and 28 October and 10 November 2003) at the same site. This study suggests that H. virescens is an established parasite of H. axyridis in Pennsylvania but that field estimates of infection may vary considerably between dates that adult beetles arrive and depart from overwintering sites. Preponderance of fungal thalli on the dorsum rather than the ventrum of H. axyridis males suggests that mating behavior is not solely responsible for transmission of H. virescens from infected to noninfected adults.

Reproductive Character Displacement in Lymantria monacha from Northern Japan

Our objective was to test the hypothesis that the pheromone blend and/or diel periodicity of pheromonal communication differ in populations of the nun moth, Lymantria monacha(Lepidoptera: Lymantriidae), from eastern Asia (northern Honshu, Japan) and Central Europe (Bohemia, Czech Republic). Coupled gas chromatographic–electroantennographic detection (GC-EAD) analyses of pheromone gland extract of female L. monachafrom Japan confirmed the presence of compounds previously identified in pheromone extracts of L. monachafrom Bohemia, as follows: (Z)-7-octadecene, 2-methyl-(Z)-7-octadecene (2me-Z7–18Hy), cis-7,8-epoxy-octadecane (monachalure), and cis-7,8-epoxy-2-methyloctadecane (disparlure). Field experiments in Honshu suggested that (+)-monachalure is the major pheromone component of L. monacha. 2me-Z7–18Hy significantly enhanced attractiveness of (+)-monachalure. Addition of (+)-disparlure to (+)-monachalure plus 2me-Z7–18Hy in Honshu and Bohemia increased attractiveness of lures by 1.2 and 20 times, respectively, indicating that (+)-disparlure is of least and most significance in the respective L. monachapopulations. Moreover, capture of male L. monachain pheromone-baited traps between 18:00 and 24:00 hr in Bohemia and 2:00 and 5:00 hr in Honshu revealed a markedly different diel periodicity of pheromonal communication. Pheromonal communication late at night and use of (+)-monachalure, rather than (+)-disparlure, as the major pheromone component by L. monachain Honshu may have resulted from interspecific competition with coseasonal L. fumida, which uses the early night for pheromonal communication and (+)-disparlure as major pheromone component. Whether communication channel divergence of L. monachain Honshu indeed constitutes a case of reproductive character displacement is difficult to prove. The evolution of such divergence in sympatricpopulations of L. fumidaand L. monachawould have to be demonstrated.

Enantiomers of (Z,Z)-6,9-Heneicosadien-11-OL: Sex Pheromone Components of Orgyia detrita

Abstract(6Z,9Z,11S)-6,9-Heneicosadien-11-ol (Z6Z9-11S-ol-C21) and (6Z,9Z,11R)-6,9-heneicosadien-11-ol (Z6Z9-11R-ol-C21) were identified as major sex pheromone components of female tussock moths, Orgyia detritaGuérin-Méneville (Lepidoptera: Lymantriidae), on the basis of (1) analyses of pheromone gland extracts of female O. detrita by coupled gas chromatographic-electroantennographic detection (GC-EAD) and GC mass spectrometry, and (2) field trapping experiments with synthetic standards. Z6Z9-11S-ol-C21 and Z6Z9-11R-ol-C21 in combination, but not singly, attracted significant numbers of male moths. Racemic Z6Z9-11-ol-C21 was more attractive than the 1:3.5 (R:S) blend ratio found in pheromone gland extracts from female moths. Lower and higher homologues of Z6Z9-11-ol-C21 were also detected in GC-EAD recordings of pheromone extracts, and the racemic compounds enhanced attractiveness of Z6Z9-11-ol-C21 in field experiments. Because of trace amounts of these homologues in extracts, their enantiomeric composition could not be determined. This is the first report of secondary alcohols as pheromone components in the ditrysian (advanced) Lepidoptera.

SEX PHEROMONE COMPONENTS OF PINK GYPSY MOTH, LYMANTRIA MATHURA

Abstract. Pheromone extract of female pink gypsy moth, Lymantria mathura, was analyzed by coupled gas chromatographic-electroantennographic detection (GC-EAD) and coupled GC-mass spectrometry (MS), employing fused silica columns coated with DB-5, DB-210, or DB-23 and a custom-made GC column that separated enantiomers of unsaturated epoxides. These analyses revealed (9R,10S)-cis–9,10-epoxy-Z3,Z6-nonadecadiene [termed here (+)-mathuralure] and (9S,10R)-cis–9,10-epoxy-Z3,Z6-nonadecadiene [termed here (–)-mathuralure] at a 1 : 4 ratio as major candidate pheromone components. In field experiments in northern Japan (Morioka, Iwate Prefecture and Bibai, Hokkaido Prefecture), (+)- and (–)-mathuralure at a ratio of 1 : 4, but not 1 : 1 or singly, were attractive to male L. mathura. This is the first demonstration that attraction of male moths required the very same ratio of pheromone enantiomers as produced by conspecific females. Whether L. mathura employ different blend ratios in different geographic areas, and the role of five additional candidate pheromone components identified in this study remains to be investigated.

Pheromone components and diel periodicity of pheromonal communication in Lymantria fumida

Extracts of pheromone glands from female Lymantria fumida were analyzed by coupled gas chromatographic–electroantennographic detection (GC-EAD) and by coupled GC–mass spectrometry (MS). The two compounds that elicited responses from male L. fumida antennae were identified as cis-7,8-epoxy-2-methyloctadecane (disparlure) and 2-methyl-Z7-octadecene (2me-Z7–18Hy). Field experiments in northern Japan demonstrated that synthetic (7R,8S)-cis-7,8-epoxy-2-methyloctadecane [(+)-disparlure] and 2me-Z7–18Hy are synergistic sex pheromone components of L. fumida. (7S,8R)-cis-7,8-Epoxy-2-methyloctadecane [(−)-disparlure] had no behavioral effect on male L. fumida. Traps baited with (+)-disparlure and 2me-Z7–18Hy captured male L. fumida between 21:00 and 24:00 hr, whereas traps baited with (+)-monachalure [(7R,8S)-cis-7,8-epoxy-octadecane], (+)-disparlure and 2me-Z7–18Hy attracted males of the nun moth, L. monacha L., between 02:00 and 04:00 hr. Both temporal separation of pheromonal communication and specificity of pheromone blends seem to contribute to the reproductive isolation of sympatric and coseasonal L. fumida and L. monacha.

Sex ratio distortion and severe inbreeding depression in the gypsy moth Lymantria dispar L. in Hokkaido, Japan

An abnormal female producing only female progeny was found in Lymantria dispar in Hokkaido, Japan, in July 1996. Similarly, its progeny produced only females. Egg hatch rates were near 50% in all-female matrilines. Therefore, a certain cytoplasmic factor was thought to kill males in eggs differentially, resulting in only female hosts. In the next generation, the field population was estimated to contain 9.1% abnormal females. Severe inbreeding depression was also observed in egg hatch rates during confirmation of maternal inheritance. The cost of inbreeding was estimated at 0.395, which is one of the highest in insects. Inbreeding avoidance by their host has been cited as one of the advantages of a male-killing factor, but we suggest that this is not applicable in this moth.

Local mate competition in the solitary parasitoid wasp Ooencyrtus kuvanae

Local mate competition (LMC) occurs when brothers compete with each other for mating opportunities, resulting in selection for a female-biased sex ratio within local groups. If multiple females oviposit in the same patch, their sons compete for mating opportunities with non-brothers. Females, in the presence of other females, should thus produce relatively more sons. Sex ratio theory also predicts a more female-biased sex ratio when ovipositing females are genetically related, and sex-ratio responses to foundress size if it differentially affects fitness gains from sons versus daughters. The mating system of the parasitoid wasp Ooencyrtus kuvanae meets assumptions of LMC. Females insert a single egg into each accessible egg of gypsy moth, Lymantria dispar, host egg masses. Wasps complete development inside host eggs and emerge en masse, as sexually mature adults, resulting in intense competition among brothers. We tested the hypothesis that O. kuvanae exhibits LMC by manipulating the number of wasp foundresses on egg masses with identical numbers of eggs. As predicted by LMC theory, with increasing numbers of wasp foundresses on an egg mass, the proportions of emerging sons increased. In contrast, the presence of a sibling compared to a non-sibling female during oviposition, or the size of a female, did not affect the number or sex ratio of offspring produced. The O. kuvanae system differs from others in that larvae do not compete for local resources and thus do not distort the sex ratio in favor of sons. With no resource competition among O. kuvanae larvae, the sex ratio of emergent son and daughter wasps is due entirely to the sex allocation by ovipositing wasp foundresses on host egg masses.

Evidence for acoustic communication in the parasitoid wasp Glyptapanteles flavicoxis

Females of the parasitoid wasp Glyptapanteles flavicoxis (Marsh) (Hymenoptera: Braconidae) deposit sex pheromone on substrate that elicits attraction and wing fanning in conspecific males. We tested the hypothesis that wing fanning sound induces a behavioral response from females which, in turn, affects the males’ orientation toward them. Females exposed to playback of the males’ wing fanning sound engaged in short flights, with sound characteristics different from those of the males’ wing fanning sound. In two‐choice bioassays, playback of the females’ flight sound attracted significantly more males than a silent control stimulus, and in combination with pheromone‐containing body extract of females it attracted more males than female body extract alone. Our data support the conclusion that the males’ wing fanning induces sound and visual reply signals from females that help males orient toward them.

2-Methyl-(Z)-7-octadecene : Sex pheromone of allopatric Lymantria lucescens and L. serva

Our objective was to identify the sex pheromone of Lymantria lucescens and Lymantria serva (Lepidoptera: Lymantriidae), whose larvae defoliate, respectively, Quercus spp. in temperate regions and Ficus spp. in the subtropics. Coupled gas chromatographic-electroantennographic (GC-EAD) detection analyses of pheromone gland extracts revealed one EAD active compound produced by female L. lucescens and by female L. serva. This was identified as 2-methyl-(Z)-7-octadecene (2me-Z7-18Hy) by retention index calculations on DB-5, DB-23, and DB-210 columns and by comparative GC-mass spectrometric (MS) and GC-EAD analyses of the insect-produced candidate pheromone and synthetic 2me-Z7-18Hy. In field experiments, traps baited with 2me-Z7-18Hy captured male L. lucescens near Toyota City, Japan, and male L. serva in Taipei, Taiwan. Allopatric distribution of L. lucescens and L. serva seems to allow both species to use the same sex pheromone without compromising its specificity.

(7R,8S)-cis-7,8-EPOXY-2-METHYLOCTADEC-17-ENE: A NOVEL TRACE COMPONENT FROM THE SEX PHEROMONE GLAND OF GYPSY MOTH, Lymantria dispar

Considering the vast Eurasian distribution of gypsy moth, Lymantria dispar (Lepidoptera: Lymantriidae), the many subspecies, and their presence in different lymantriid communities, we tested the hypothesis that L. dispar populations in eastern Asia employ one or more pheromone components in addition to the previously known single component pheromone (7R,8S)-cis-7,8-epoxy-2-methyloctadecane [= (+)-disparlure]. Coupled gas chromatographic–electroantennographic detection (GC–EAD) analyses of pheromone gland extracts of female L. dispar sensu lato (including both AGM and NAGM) on four GC columns (DB-5, DB-23, DB-210, and SP-1000) revealed a new trace component that eluted just before (DB-5; DB-210) or after (DB-23, SP-1000) disparlure, and elicited strong antennal responses. Isolation of this compound by high-performance liquid chromatography and hydrogenation produced disparlure, suggesting that the new component had the molecular skeleton of disparlure, with one or more double bonds. Of all possible monounsaturated cis-7,8-epoxy-2-methyloctadecenes, only cis-7,8-epoxy-2-methyloctadec-17-ene co-chro- matographed with the insect-produced compound on all GC columns and elicited comparable antennal responses. In field experiments in Honshu (Japan) with enantioselectively synthesized compounds, (7R,8S)-cis-7,8-epoxy-2- methyloctadec-17-ene (7R8S-epo-2me-17-ene-18Hy) was weakly attractive to male L. dispar, but was less effective as a trap bait than (+)-disparlure, and failed to enhance attractiveness of (+)-disparlure when tested in blends. The antipode, (7S,8R)-cis-7,8-epoxy-2-methyloctadec-17-ene, was not attractive, and when added to (+)-disparlure and/or 7R8S-epo-2me-17-ene-18Hy reduced attractiveness. Thus, the biological role of 7R8S-epo-2me-17-ene-18Hy remains unclear. It may enhance pheromone attractiveness or specificity in other L. dispar populations within their vast Eurasian distribution.