A. A. Grigarick

Diel flight periodicities of some Dytiscidae (Coleoptera) associated with California rice paddies

Abstract. Diel flight periodicities of Eretes sticticus (L.), Hygrotus medialis (LeConte), Laccophilus mexicanus atristernalis Crotch, Liodessus affinis (Say) and Thermonectus basillaris (Harris) were monitored with a rotary net machine and a black light trap. All were affected to some extent by air temperature, light intensity, and wind velocity.

Economic Thresholds and Injury Levels for Insect Pests of Rice

Over 90% of the world’s rice is grown in Asia where more than 100 insect species attack the crop (Norton and Way 1990). Other rice-growing areas each with a unique complex of insect pests include Latin America, Africa, Australia, Europe, and the United States. Insects are a major constraint to world rice production which must increase from current levels of 460 to 760 million tons simply to keep pace with human population growth as projected for 2020 (Woodburn 1990). On a global scale, insects decrease rice yields an estimated 26% (Cramer 1967). The economic importance of insect pests of rice is illustrated by the fact that

Habits and relative population densities of some hydrophilids in California rice fields

910 million was spent throughout the world on insecticides applied to rice in 1988 (Woodburn 1990).

A new Neotropic genus of Pyxidicerini (Coleoptera: Pselaphidae)

Populations of the hydrophilids Berosus styliferus Horn, Hydrophilus triangularis Say, and Tropisternus lateralis (Fabricius) were observed in northern California rice paddies. Relative adult and larval density for each species was determined using aquatic light traps adjacent to the water margin, and at 5 m and 30 m distances from the levee. Egg cases were monitored by recording numbers per unit area.The seasonal patterns of abundance indicate each species has a univoltine life cycle. All stages of B. styliferus and H. triangularis are more abundant nearer the levees. T. lateralis adults are commonly found at the levees during the first 10 weeks post-flood, whereas T. lateralis larvae and egg cases are most numerous at the 30 m distance.Colonication of the paddies occurs through water connections, flight, and adult overwintering.

Biological Control of Aster Leafhopper (Homoptera: Cicadellidae) and Midges (Diptera: Chironomidae) by Pardosa ramulosa (Araneae: Lycosidae) in California Rice Fields

The pselaphid beetle tribe Pyxidicerini in the neotropics is redefined to include genera with eleven antennomeres and without maxillary fossae. The genera Barroeuplectoides, Tuberoplectus (formerly Euplectini) and Ocabajara n.gen. are placed in the tribe on the basis of sternal, tarsal and abdominal characteristics which are identical to those of Bythinoplectus.