John D. Lattin

Insect conservation and pest management

The issue of insect conservation in pest management has many conflicting aspects. For instance, it is desirable to conserve a pest residue in order to maintain natural enemy population and it is imperative to conserve natural enemies. However, conservation of pest species is not relevant if the pest species is an exotic invader and a candidate for eradication, mainly because eradication, if successful, achieves only regional extinction. Conservation of native pests depends, to a large extent, on whether the species is a direct pest of a high value crop or an indirect pest with an acceptable economic injury level. In this paper, integrated pest management is defined in terms of sustainable agriculture and the conservation of biodiversity, and give five premises that stress the level of disturbance of agricultural communities and the dynamics of pest status for arthropod species in the community. The possible impacts of the main integrated pest management tactics on arthropod conservation are tabulated and the results reached stress that diversification of agricultural systems through maximum use of native plants should benefit both integrated pest management and regional arthropod conservation.

Paracentric inversion polymorphism in the grasshopper Boonacris alticola

Paracentric inversion heterozygosity can be detected at pachytene by observation of frequent regions of asynapsis and reinforced by observation of the elimination of a chiasma in the region of the inversion at diplotene and by a low level of bridges and fragments at anaphase. We present evidence that paracentric inversion polymorphism can persist in a grasshopper population despite a low level of crossing over within the inverted region in heterozygotes. Lethality resulting from aneuploidy due to limited crossing over within the region of the inversion appears to be more than compensated for by heterosis.

OBSERVATIONS OF SELECTED TRUE BUGS (HEMIPTERA: HETEROPTERA) OF THE PACIFIC NORTHWEST SHRUB-STEPPE ZONE

The shrub-steppe zone of the Pacific Northwest extends over a vast interior region. Bailey (1998) published a broadscale treatment of the ecoregions of the world, complete with a detailed map. Much of western North America is included in the Temperate Steppe Division, Temperate Steppe Regime Mountains, and the Temperate Desert Division. Houghton (1986) provided an account of the Great Basin that includes parts of California, Idaho, Nevada, Oregon, and Utah. Franklin and Dyrness (1988) included the Columbia Basin, the High Lava Plains, the Owyhee Upland, and the Basin and Range as physiographic and geological provinces of Oregon and Washington. Thorson et al. (2003) published a detailed map of the ecoregions of Oregon where most of eastern Oregon was encompassed in the Columbia Plateau, Blue Mountains, Cascades Slopes and Foothills, and northern Basin and Range. The Columbia River basin includes portions of Idaho, California, Nevada, and Oregon (Lattin 1995). A number of plants in the Pacific Northwest shrub-steppe zone respond early in the season when moisture is limited. Early season temperatures, near freezing at night and in early morning, warm gradually as the season progresses. Insects adapted to feed on such plants must cope with the lower temperatures and respond to the early pulse of new growth. Knowledge of insects characteristic of shrubsteppe habitats is still rather sparse, even though these organisms surely exhibit greater species diversity than any other group in this region. Many plant taxa are broadly distributed in this zone (Franklin and Dyrness 1988), for example, Artemesia and Purshia. While little is known about the distribution and habits of most insects and mites found on these plants, Kraft (1960) cited more than 250 species he collected on bitterbrush, Purshia tridentata (Pursh.) DC., in portions of the shrub-steppe in the Pacific Northwest during 1957 and 1958. Lattin (1995) estimated that 30 families, 163 genera, and 307 species of true bugs (Hemiptera: Heteroptera) occurred in the Columbia River basin area encompassing several states and extensive areas of shrub-steppe habitats. The variety of introduced plants (accidental and deliberate) has adversely affected native plants, while some have been colonized and injured by native bug species, for example, black grass bugs on introduced Agropyron species. Many species of true bugs use these early maturing plants. Since they often occur before most field work begins, several species of true bugs remain to be discovered. Some of these species belong to genera that are also represented in Central Asia but are represented only by a single species in northwestern North America. Two of the species reported here are found in both regions.