The silkworm, Bombyx mori, has been a domesticated, economically important insect for 5 000 years. Recent accomplishments in molecular immunology have revealed just a preliminary outline for silkworm innate immunity. The acquisition of the updated silkworm genome has enabled a comparative analysis of the silkworm immune-related genes and signaling pathways. In this study, through comparing with the sequenced Drosophila melanogaster, Anopheles gambiae, Apis mellifera and Tribolium castaneum genomes, we identified over 218 genes in the silkworm that fall into 21 families involved in immune defense, including pattern recognition receptors, signaling transducers, effectors and oxidative defense enzymes. Phylogenetic analysis showed that the signal transducers have remarkable orthologous relationships between different insect species in spite of the divergent sequences. In contrast, gene families associated with recognition, modulation and effectors exhibit more significant sequence conservation. However, the orthologs of these families are remarkably absent, presumably attributable to the lineage-specific gene duplication. Our results suggest that common mechanisms may be responsible for innate-immunity responses to pathogens via signaling pathways in the silkworm. Furthermore, hosts may adjust their defensive strategies by gene duplication and sequence divergence to kill pathogens.

In order to verify the activity of the heat shock protein gene expression driven by the promoter of Bombyx mori hsp20.4 gene and the effect of Bombyx mori nuclearpolyhedrosisvirus (BmNPV) egt gene products on the development of silkworm, we amplified hsp20.4 promoter and egt fragments by PCR, and then recombined hsp20.4 promoter with red fluorescent protein gene DsRed and BmNPV egt respectively to form two different recombinant vectors. The former transferred into silkworm BmN cells and tissues showed the transient expression of DsRed, indicating the hsp20.4 promoter sequence possess heat shock protein gene promoter activity in silkworm, while the latter injected into silkworm pupa could delay the pupal development of silkworm by heat induction.

Three special substrates were used in enzyme activity analysis to evaluate the effects of pH on the digestive protease activity in the midgut of locust Catantops pinguis (Stål). The results showed that the pH value in the midgut of locust had no difference between the sexes, which was 6.92±0.043 in male and 7.03±0.054 in female. Three serine digestive proteases in midgut were identified by three special substrates. The optimal pH of the active alkaline trypsin-like enzyme (BAPNA as the substrate) was 8.5 in the female and 10.5 in the male; the optimal pH of weak alkaline trypsin-like enzyme (TAME as the substrate) was 9.0 in the female and 9.5 in the male; the optimal pH of chymotrypsin-like enzyme (BTEE as the substrate) was 8.5 in the female and 8.0 in the male. The statistical results showed that pH affected the serine protease activity obviously (P<0.01), and the activity of the same protease in the female was remarkably different from that in the male (P<0.01), meaning the activity of trypsin-like enzyme in the female was higher than that in the male at the optimal pH, while the activity of chymotrypsin-like enzyme in the male was higher than that in the female at the optimal pH. In the range of pH in midgut, the female has a higher digestive protease activity than the male, suggesting that the female has a stronger capacity to deal with the food intake to get more nutrients for reproduction (forming eggs). The digestive proteases remain active over a wide pH range, which may give this locust an adaptive advantage of feeding on a wide range of plants in the field.

In order to clarify the difference of pyrethroid metabolosim between resistant and susceptible strains, deltamethrin and cypermethrin reporter fluorescent substrates with fluorescent characteristics after hydrolysis were synthesized and used to assay carboxylesterase metabolic activities in different strains of cotton aphid, Aphis gossypii. The results showed that the specific carboxylesterase activities to deltamethrin reporter fluorescent substrate were 10.0 and 3.4 pmol/min·mg in the omethoate-selected resistant and susceptible strains of cotton aphid, respectively, while those to cypermethrin reporter fluorescent substrate were 4.0 and 2.4 pmol/min·mg, respectively. The carboxylesterase activity in the omethoate-selected resistant strain was 2.94- and 1.67- fold compared with that in the susceptible strain when using deltamethrin and cypermethrin reporter fluorescent substrates, respectively. However, the specific carboxylesterase activities to deltamethrin reporter fluorescent substrate were 7.6 and 6.2 pmol/min·mg in the deltamethrin-selected resistant and susceptible strains of cotton aphid, respectively, while those to cypermethrin reporter fluorescent substrate were 9.3 and 5.2 pmol/min·mg, respectively. The carboxylesterase activity in the deltamethrin-selected resistant strain was 1.23- and 1.79-fold compared with that in the susceptible strain when using deltamethrin and cypermethrin reporter fluorescent substrates, respectively. The surrogates for pyrethroids can be used to monitor carboxylesterase hdyrolytic activity of resistant cotton aphids, suggesting that carboxylesterases may be involved in deltamethrin and omethoate resistance in cotton aphids.

In order to study the effect of 12a-hydroxyrotenone on the fecundity of Prodenia litura (Fabricius) and its action mechanisms, the number of eggs laid per female adult of P. litura was investigated; after 12a-hhydroxyrotenone in ovary was determined with HLPC, its cytotoxicity to ovarian cells from P. litura(PL cells) was determined at 48 h after treatment by MTT assay. The effect of 12a-hydroxyrotenone on cell cycle, cell membrane potential and mitochondrial membrane potential of PL cells, and intracellular free calcium concentration in PL cells at 24 h after treatment was also tested by flow cytometry. The results showed that the number of eggs laid per female adult declined by above 80% after 12a-hydroxyrotenone was fed to P. litura larvae, and the compound could be detected from the ovarian tissues. 12a-hydroxyrotenone showed inhibitory activity to PL cells, with IC₅₀being 6.6 mg/L at 48 h after exposure. After PL cells were treated with 12a-hydroxyrotenone for 24 h, the percentage of S phase cells markedly increased in cultured PL cells (P<0.05), while the percentage of G₂-M phase cells decreased. Cell membrane potential, mitochondrial membrane potential and the intracellular free calcium concentration in PL cells were significantly higher than those of the control groups. 12a-hydroxyrotenone led to a linear decrease in the number of eggs laid per female and PL cell cycle arrest in S phase. 12a-hydroxyrotenone exhibited weak cytotoxicity to PL cells, and caused some of them to death. Thus the number of ovarian cells decreased, and the ovary development was inhibited so that ovarian cells could not develop into mature ooctyes and its fecundity obviously decreased.

To study the effects of photoperiod and temperature on the diapause induction in the beet webworm Loxostege sticticalis, the interactive effects of temperature (18, 22, 26 and 30℃) and photoperiod (L8∶D16, L10∶D14, L12∶D12, L14∶D10 and L16∶D8) on diapause induction in this moth were investigated by artificial induction method in the laboratory. The photoperiod played the key role in diapause induction in mature larvae, followed by temperature and their interaction. Photoperiod response in L. sticticalis showed that it is a typical longday species with a critical day length of 13.97, 14.48, 13.92 and 12.88 h at 18, 22, 26 and 30℃ respectively. The day length of 12 h resulted in the highest diapause rate at all the experimental temperatures. The larvae of 11 to 17 days after hatching (about in the 5th instar) were most sensitive to the photoperiod, suggesting that the 5th instar is the most sensitive stage of diapause induction. However, the short daylight received by the 4th instar larvae was also important for the increase of their diapause rate, which can be increased from 40.0% to 90.0%.

The spiralling whitefly, Aleurodicus dispersus Russell, is a newly destructive invasive pest in Hainan Island, China. The morphology and biology of the spiralling whitefly were studied systematically through observations and experiments both in fields and laboratory. The results showed that the developmental threshold and the effective accumulative temperature for whole generation were estimated to be 8.88℃ and 511.86 degree-days, respectively, and 8-9 generations could occur per year in Hainan Island. In the temperature range of 18℃ to 32℃, the developmental duration from egg to adult is 26.63 to 57.15 d (including that for egg 7.15-15.93 d, 1st instar nymph 4.00-11.03 d, 2nd instar 3.83-7.53 d, 3rd instar 4.09-8.64 d and 4th instar 7.56-14.03 d), but the whitefly failed to survive at 14℃. The temperature higher or lower than 28℃, however, displayed negative effects on the population increase of the whitely. The adults are normally active at dawn and dusk, especially at calm, uncloudy dawn (7:00 am) or in the cloudy morning (9:00 am), but mostly inactive in rainy day.

Rattus norvegicus may be as the reservoir host of plague in some domestic plague foci of Yunnan province, and some of its ectoparasite species may be the potential vectors of human diseases. To understand the ectoparasite communities in a population of R. norvegicus in the surrounding areas of Erhai Lake and the potential medical and veterinary importance of these ectoparasites are described. Ectoparasite communities of 431 rats of R. norvegicus were studied by using Mann-Whitney U-tests and Spearman correlation analysis, which were sampled in the surrounding areas of Erhai Lake (a famous fresh water lake in Southwestern China) in Yunnan in 2003 to 2004. The constituent ratio (C), prevalence (P) and average ectoparasite abundance (A) were used to test prevalence and density of ectoparasites. The surveyed areas were located in the wild rodenttype plague focus, one of the 11 known plague foci in China and also an important focus of both scrub typhus and epidemic hemorrhagic fever (EHF). The results indicated that a high proportion (71%, 307 individuals) of the sampled 431 rats was found to be infested with ectoparasites. A total of 47 ectoparasite species, including 23 species of chigger mites, 16 species of mesostigmatid (gamasid) mites, 6 species of fleas and 2 species of sucking lice were collected from R. norvegicus. Within this ectoparasite complex, 16 species had previously been reported to be vectors of human disease agents. The results suggest that there is very high species diversity of ectoparasites of R. norvegicus.

The paper deals with 6 species of the genus Xistra Bolivar from China, including one new species from Ya′an, Sichuan, Xistra yaanensis sp. nov. A key to all species of the genus is provided. Type specimens of new species are kept in the Institute of Zoology, Shaanxi Normal University.

Cytochrome P450 monooxygenases(P450s) are a superfamily of genes encoding multifunctional heme-thiolate proteins that play a dominant role in the metabolism of a wide variety of both endogenous and xenobiotic substances. The total number of P450 genes in insects registered in the GenBank is over 1 000. Most of the registered P450 gene sequences are from Diptera (74%) and Lepidoptera (16%). Of the total full-length sequences of P450 genes of insects registered, 20% are CYP6 members and 45% CYP4 members. A novel phylogenetic tree of the insect P450 superfamily which expounds evolutionary relationship of different subfamilies and orders was here constructed using a multiple alignment of the registered insect P450 sequences. The relationships of insect orders revealed by the phylogenetic tree most match the evolutionary relationships of insect orders based on other molecular data or morphological taxonomy. The present research indicates that the expression of cytochrome P450 genes may be regulated by cis-acting element or/and trans-acting factor, and the regulation mechanisms may involve the transcription enhancement (transcriptional mechanism) or an increase in mRNA stability (post-transcriptional mechanism).

Entomopathogenic nematodes are important biological control agents of insect pests. The tolerance capability of the nematodes to the abiotic stress may greatly affect the survival and performance in pest control in fields. Response of entomopathogenic nematodes to abotic stress is complex and involves the processes of variation of population genetic, life stage, biochemical and physiological changes, and differential expression of related genes. This paper reviews the recent research progress in response mechanisms of entomopathogenic nematodes to abiotic stress, mainly focusing on the achievements in identification and function analysis of tolerance-related genes of entomopathogenic nematodes. The trends of this research field are also discussed. We expect to provide some useful information for conducting similar research in China.

Drywood termite Cryptotermes domesticus (Haviland) is a serious pest causing wood damage. It is one of the most important termite species in China. This paper summarizes the progress in biological and ecological studies on the formation, survival, reproduction and dispersal of neotenics, the swarming of mature colonies, life cycle and behavioral feature of primary reproductives, and the formation, development and feeding behavior of the new colony of C. domesticus. The control strategy against C. domesticus is also discussed. The study may provide theoretical basis for controlling the spread, diffusion and damage of C. domesticus.

To investigate the differential expression of protein components in the newly-hatched male and female larvae of a temperature-sensitive silkworm variety, Xianban, we compared the protein components of the newly-hatched female (black) and male (red) larvae by using two-dimensional electrophoresis technology. The results showed that 269 and 250 protein spots were detected in easily dissolvable proteins from the newly-hatched male and female larvae respectively. Comparison analysis showed that 86.71% of the total protein spots were matched between male and female larvae, and 43 and 25 specific proteins were found in male and female larvae respectively. In uneasily dissolvable proteins from the newly-hatched male and female larvae, 370 and 424 protein spots were detected respectively. Comparison analysis showed that 80.10% of the total protein spots were matched between the two groups, and 52 and 106 specific proteins were found in male and female larvae respectively. The results indicated that the protein components of the newly-hatched larvae of the silkworm variety are different between the male and female.

The behavior, mortality and reproduction of Callosobruchus maculates in response to β-asarone derived from Acorus calamus were studied in the laboratory. The results showed that the contact toxicity symptoms included restlessness, loss of coordination, knockdown and eventual death of adult beetles. β-asarone caused 100% mortality of C. maculates at 64 h post treatment. Significantly lower mating number was observed in C. maculates treated with β-asarone than in the untreated beetles, and the mating number reduced with the exposure time. Significant lower mating competition was observed in C. maculates males than in females in response to β-asarone. The numbers of eggs laid by the female were all significantly lower in both the treatment of the treated female mating with the untreated male and the treatment of the treated male mating with the untreated female than that of the control, which was also decreased with the exposure time, but no difference was observed between the two treatments. The egg hatching rates of the laid eggs were also all significantly lower in both the treatments than that of the control, which was not decreased with the longer exposure to β-asarone, and there was also no difference in egg hatching rate between the two treatments. So it is concluded that β-asarone extracted from A. calamus is a nerve agent, which can reduce the population size of the progeny of C. maculates, and thus can be exploited as potential insecticide against C. maculates.