Biological and biochemical characterization of a red-eye mutant in Nilaparvata lugens （Hemiptera： Delphacidae）

A red-eye colony was established in our laboratory in brown planthopper （BPH）, Nilaparvata lugens （Stal）, a major rice pest in Asia. Except for the red-eye phenotype, no other differences were observed between the wild-type （brown eye） and the mutant-type （red eye） in external characters. Genetic analysis revealed that the red-eye phenotype was controlled by a single autosomal recessive allele. Biological studies found that egg produc- tion and egg viability in the red-eye mutant colony were not significantly different from those in the wild-type BPH. Biochemical analysis and electronic microscopy examination revealed that the red-eye mutants contained decreased levels of both xanthommatin （brown） and pteridine （red） and reduced number of pigment granules. Thus, the changes of amount and ratio of the two pigments is the biochemical basis of this red-eye mutation. Our results indicate that the red-eye mutant gene （red） might be involved in one common gene locus shared by the two pigments in pigment transportation, pigment granule formation or some other processes.     

Influence of light and habitat on predation of Culex quinquefasciatus （Diptera： Culicidae）larvae by the waterbugs （Hemiptera： Heteroptera）

The influence of light and habitat structure on the predation of Culex quinquefasciatus larvae by the common heteropteran water bug, Diplonychus （= Sphaerodema） annulatus, D. rusticus and Anisops bouvieri was assessed in the laboratory. It was revealed that water bugs predate more in presence of light than in dark conditions. While A. bouvieri consumed more prey in structured conditions, D. annulatus and D. rusticus consumed more prey in open conditions. The selection of prey size as well as the respective numbers varied between predators and treatments significantly. Prey vulnerability （PV）, an indicator of predatory efficiency, was highest for D. annulatus, moderate for D. rusticus and low for A. bouvieri. Prey consumption and PV values under different treatment conditions indicate that for belostomatid water bugs D. annulatus and D. rusticus, the order of prey consumption under different habitat and light/dark combinations is light open 〉 dark open 〉 light vegetated 〉 dark vegetated. In the case of the backswimmer, A. bouvieri, the order of prey consumption appeared to be light structured 〉 dark structured 〉 light open 〉 dark open. These findings were consistent with resource-partitioning by water bug species sharing the same guild. If the observed results are extended to natural settings the efficiency of these predators in controlling mosquito populations will vary with the structural complexity of habitats and the intensity of light.     

Comparison of the potential rate of population increase of brown and green color morphs of Sitobion avenae （Homoptera： Aphididae） on barley infected and uninfected with Barley yellow dwarf virus

Life tables of brown and green color morphs of the English grain aphid, Sitobion avenae （Fabricius） reared on barley under laboratory conditions at 20 ＋ 1℃,65% ± 5% relative humidity and a photoperiod of 16 ： 8 h （L ： D） were compared. The plants were either： （i） infected with the Barley yellow dwarf virus （BYDV）; （ii） not infectedwith virus but previously infested with aphids; or （iii） healthy barley plants, which were not previously infested with aphids. Generally, both color morphs of S. avenae performedsignificantly better when fed on BYDV-infected plants than on plants that were virus free but had either not been or had been previously infested with aphids. Furthermore,when fed on BYDV-infected plants, green S. avenae developed significantly faster and had a significantly shorter reproductive period than the brown color morph. There wereno significant differences in this respect between the two color morphs ofS. avenae when they were reared on virus-free plants that either had been or not been previously infestedwith aphids. These results indicate that barley infected with BYDV is a more favorable host plant than uninfected barley for both the color morphs ofS. avenae tested, particularly the green color morph.