Of the major physical factors that influence insect seasonal ecology, moisture is least understood and least appreciated. It is our premise that experimental probing of insects from diverse zones and various habitats would reveal general patterns of insect responses to moisture that are as striking as those for photoperiod and temperature. Using the paradigms of photoperiod and temperature as ecophysiological determinants of insect seasonality, we hypothesize that moisture influences insect life cycles via one or more of three mechanisms-as a token stimulus for diapause, modulator of developmental or reproductive rates, or behavioral cue for vital seasonal events. For heuristic purposes, we offer each of these hypotheses in close association with approaches for testing their validity in insects that undergo dry-season dormancy. The approaches appear appropriate for examining the role of moisture in the life histories of terrestrial invertebrates other than insects, as well as plants and microbes that have a seasonal resting stage. Elucidating moisture's role in insect seasonal cycles is critical to the development of comprehensive phenological models, improved insect management systems, and identification of novel evolutionary mechanisms for adaptation to wet-dry seasons, especially in tropical, subtropical, and Mediterranean regions.KEY WORDS phenology, moisture, soil-inhabiting insects, dormancy, development, reproduction PHOTOPERIOD ANDTEMPERATURE are generally considered prime factors in the seasonal ecology of terrestrial invertebrates (Beck 1980, Tauber et aI.1986). In contrast, moisture is usually consigned a secondary or minor role. This subordinate ranking of moisture as a seasonal cue may be grossly misleading for 2 reasons: First, phenological studies are concentrated in the Temperate Zone where large seasonal changes in photoperiod and temperature typically occur. Consequently, investigators are heavily biased toward using photoperiod and temperature as variables, and data on moisture's function and significance are lacking. Second, the natural histories of a large proportion of earth's insects (e.g., those from tropical, Mediterranean, and other regions with conspicuous wet and dry seasons) are highly correlated with changes in moisture conditions (Essig 1926, Edney 1977, Wolda 1978, Shapiro 1979, Mooney et al. 1980, Labeyrie 1981, King 1984, Denlinger 1986, Paarmann 1986, Powell 1986, Brakefield 1987, Dobkin et a1.1987, Janzen 1987, Bradshaw and Holzapfel 1988, Clouds ley-Thompson 1991, Hadley 1994, Somme 1995. Indeed, it appears that cycles of rainfall and moisture in wet-dry regions may rival those of temperature in temperate regions, in both their seasonal predictability and their importance for survival and development of insects. Thus, we contend that moisture constitutes a greatly un-

For those arthropod species adapted for living below the soil surface, the soil is a refuge from the biotic and abiotic perturbations existing above ground. Convergent morphological, physiological, and behavioral adaptations of epedaphic, euedaphic, and hemiedaphic arthropods to selective aspects of subterranean existence are examined in light of overlapping ecological niches. The abiotic impact of the soil environment and its relationship to arthropod evolution, radiation, and ecology are discussed as well. Specific areas addressed include the invasion of land by marine arthropods, the impact of morphology on arthropod mobility, osmoregulatory/respiratory systems, and defensive strategies.

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The effect of soil moisture on entomopathogenic nematode virulence was examined in the laboratory. Objectives were to determine the virulence of several species and isolates of entomopathogenic nematodes at various soil moisture contents and temperatures, and after ßuctuations in soil moisture. Studies included up to Þve isolates of entomopathogenic nematodes: Heterorhabditis bacteriophora Poinar (Oswego and Tuscarora strains), Steinernema glaseri (Steiner) (NC1 strain), S. feltiae (Filipjev) (Biosys 369 strain), and S. carpocapsae (Weiser) (NY001 strain). Nematodes were applied to sandy loam soils ranging in soil moisture content from below the permanent wilting point of plants to near saturation. In all experiments, a rainfall or irrigation event was simulated by adding water to rehydrate soils to high moisture levels (near saturation). Nematode virulence was evaluated periodically by measuring insect mortality in Galleria mellonella (L.) larval bioassays, before and after rehydration. Nematode virulence increased with soil moisture content for all species and isolates tested. Our studies demonstrated that the virulence of entomopathogenic nematodes in low moisture conditions could be restored by rehydrating the soil. Insect mortality was generally low in lowmoisture, nematode-infested soils before rehydration, but increased to high levels posthydration. Moisture effects were evident from the onset of each experiment, whereas the effect of soil temperature on nematode-induced insect mortality was delayed and nonsigniÞcant until 14 wk after the initiation of the third experiment.

The synthetic female sex pheromone of the oriental beetle, Anomala orientalis Waterhouse, was evaluated in the field and in a sustained-/light tunnel. In a 2-wk period, >150,000 beetles were captured on three golf course fairways in Connecticut.Contrary to earlier reports that these beetles are most active during the warm, sunny portions of the day, we observed that peak activity occurs around sunset. Ten micrograms of either (Z)-7-tetradecen-2-one or an 89/11 (Z/E) blend on a rubber septum was found to be the minimum concentration with which no significant decrease in catch was observed in the field. There was no discrimination between Z and the blend at 1 J.'g and higher concentrations, but the E-isomer alone trapped significantly fewer beetles than either Z alone or the blend. These results are consistent with the /light tunnel data. The effects of temperature and light intensity on the mating behavior of A. orientalis also are discussed.

Females of the Oriental beetle,Anomala orientalis (Waterhouse), release a sex pheromone composed of a 9:1 blend of (Z)- and (E)-7-tetradecen-2-one. The double-bond position of the pheromone was determined by DMDS derivatization and interpretation of the fragmentation patterns produced by monounsaturated ketones. In a sustained-flight tunnel, males responded by flying toward female beetles and attempting to copulate with them. Both effluvium and whole-body extracts of OB females were analyzed, and the activity was found only in the airborne extracts. Flight-tunnel bioassays also showed that a synthetic 90:10Z/E blend on a rubber septum was attractive and that the responses of males to this blend were equivalent toZ isomer alone, but much better than to the singleE isomer.

Bulb mites of the genus Rhizoglyphus (Claparède) (Acari: Acaridae) have been identified as pests of many crops and ornamentals in storage, in the greenhouse, and in the field. The most important hosts are species in the family Liliaceae (e.g. Allium spp.), but bulb mites will often attack other important crops such as potatoes (Solanum sp.) and carrots (Daucus carota). Despite their economic importance and broad distribution, the systematics of the genus remains in a state of confusion and is in need of a comprehensive revision. In addition, the field biology and ecology of these mites is not well understood, and methods for sampling, monitoring, and loss assessment are limited. Management of bulb mites is complicated by their short generation time, high reproductive potential, broad food niche, interactions with other pests and pathogens, and unique adaptations for dispersal. Historically, control of these acarine pests has relied on the use of synthetic miticides and insecticides, but this option is now limited due to documented resistance and withdrawal of registration of some products. Alternative control strategies, including cultural and biological control, have shown limited success, but need to be further developed and implemented.

Abstract-Chiral capillary gas chromatographic-electroantennographic detection (GC-EAD) analysis indicates that L-valine and L-isoleucine methyl esters are the major sex pheromone components released by females of the cranberry white grub, Phyllophaga anxia (LeConte). The GC retention times and GCmass spectrometry of the two natural compounds were identical to those of authentic standards. Of five reproducible GC-EAD active components revealed with female volatiles, the L-valine and L-isoleucine methyl esters elicited the strongest male antennal responses. The ratio of L-valine and L-isoleucine methyl esters was determined to be 3:1 by analysis of pheromone gland extracts. Chirality was shown to be critical by GC-EAD, since only the L-form of these amino acid methyl esters elicited an EAD response. In field experiments conducted in Massachusetts, a synthetic 3:1 blend of L-valine and L-isoleucine methyl esters on a rubber septum was attractive to P. anxia males.