Bulletin of Entomological Research最新文献

The effect of climate factors (temperature, humidity, precipitation, and frost days) on the population changes, damage, and infestation area of the leopard moth, Zeuzera pyrina L., was studied during 2006-2018 in four parts of Iran including Saman, Arak, Najaf-abad, and Baft. For trend analysis, the Mann-Kendall test was run on time series data of both climate and pest population. According to the results, the annual mean (Kendall's statistics, T = 0.64 and 0.48), annual minimum (T = 0.60 and 0.42), and January mean (T = 0.64 and 0.61, respectively) temperatures showed increasing trends in Saman and Najaf-abad. Moreover, the annual mean minimum and January temperatures (T = 0.41 and 0.45, respectively) in Arak and the annual mean maximum temperature (T = 0.79) in Baft showed increasing trends. The number of frost days/year (Kendall's statistics, T = -0.63, -0.53, -0.32 and -0.37) and annual mean relative humidity (T = -0.43, -0.63, -0.64 and -0.42, respectively) showed decreasing trends in Saman, Arak, Baft, and Najaf-abad stations. Trend analysis indicated significant increases in the mean number of moths caught (T = 0.59, 0.76 and 0.90), the percentage of infested branches/tree (T = 0.66, 0.58, and 0.90), the number of active holes/tree (T = 0.79, 0.55, and 0.68) and the infested areas (T = 0.99, 0.73, and 0.98, respectively) in Saman, Arak and Najaf-abad stations. According to stepwise regression, the mean temperatures of January, autumn, and winter were the most effective variables for increasing Z. pyrina damage and population, while relative humidity and the number of frost days played the major role in reducing it.

Lablab purpureus subsp. bengalensis (Jacq.) Verdc. is an important legume of India and Africa. Both aphids, Aphis craccivora Koch and A. gossypii Glover (Hemiptera: Aphididae), are important herbivorous pests of this legume crop. These viviparous females lay nymphs on the leaf surface of this legume plant. Therefore, it is of considerable interest to study whether leaf surface wax chemicals (long-chain alkanes and free fatty acids) of this legume plant served as short-range attractants and oviposition stimulants in both females to lay nymphs. Twenty-one n-alkanes from n-C₁₂ to n-C₃₅ and 11 free fatty acids from C12:0 to C22:0 were identified in leaf surface waxes. Nonacosane and nonadecanoic acid were the most abundant among n-alkanes and free fatty acids, respectively. Both females were attracted towards one leaf equivalent surface wax against the control solvent (petroleum ether) in short Y-tube olfactometer bioassays. A synthetic blend of tetradecane, pentadecane, tetracosane, tridecanoic acid, tetradecanoic acid, and heneicosanoic acid comparable to one leaf equivalent surface wax served as short-range attractants and oviposition stimulants in A. craccivora; whereas a synthetic blend of tetradecane, hexadecane, docosane, nonadecanoic acid, and arachidic acid comparable to one leaf equivalent surface wax acted as short-range attractants and oviposition stimulants in A. gossypii. These results can provide the basis for efficient pest management strategies of A. craccivora and A. gossypii against L. purpureus subsp. bengalensis using host plant leaf surface wax compounds. Further, SEM studies of antennae and forelegs of both aphids were conducted to observe sensilla structures, which help in chemoreception.

Habitat selection of Culicoides spp. (Diptera: Ceratopogonidae) is influenced by the physicochemical factors such as temperature, pH, salinity, moisture, conductivity, organic and inorganic compounds of substrates. These factors determine the life history traits of the vectors. We studied the influence of substrate salinity (0-40 parts per thousand, ppt) and pH (pH 1-13) on oviposition, egg hatching, larval survivability, and adult emergence of Culicoides peregrinus Kieffer under laboratory conditions. Most eggs (80.74%) were laid in 0 ppt and 95% in pH 7 but lowered with increased salinity and pH levels. It was observed that the females did not lay eggs in 30 ppt to 40 ppt salinity; pH 1 and pH 13 but interestingly up to 95% of the eggs were retained within the abdomen. Little effect of salinity and pH on egg hatching was observed up to 5 ppt and 10 ppt except at the extreme values of 40 ppt and pH 1, pH 13. Pupation did not occur in rearing plates with high salinities, 30 ppt and 40 ppt, although the few eggs hatched when exposed to such salinity. In low salinity (0 to 2 ppt), occurrence of adult emergence was more and then decreased with increasing salinity. Maximum emergence was seen when the rearing media was alkaline. This study deals with the suitability of breeding substrate of C. peregrinus when exposed to salinity and pH ranges. Our study suggests the ambient salinity and pH ranges to be maintained during laboratory rearing of this vector species.

Climate factors, pesticides, and landscape in coffee agroecosystems directly affect the populations of the coffee leaf miner and its parasitoids. This study aimed to investigate the effects of climate factors, insecticide use, and landscape on natural parasitism, parasitoid diversity, and infestation of L. coffeella in coffee plantations in the Planalto region, Bahia, Brazil. Mined leaves were collected monthly in six coffee plantations with varying edge density, vegetation cover, landscape diversity in scales of 500 to 3000 m of radius, insecticide use, and climate factors. Closterocerus coffeellae, and Proacrias coffeae (Eulophidae) predominated in the pest's natural parasitism. Our record is the first for the occurrence of Stiropius reticulatus, Neochrysocharis sp. 1, Neochrysocharis sp. 2, and Zagrammosoma sp. in Bahia. Higher temperature and larger forest cover increased the coffee leaf miner infestation. Higher rainfall values, insecticide use, and landscape diversity decreased the pest infestations. Natural parasitism and species diversity are favoured by increase in temperature, forest cover, and edge density, while increase in rainfall, insecticide use, and landscape diversity lead them to decrease.The natural parasitism and diversity of parasitoid species of the coffee leaf miner have been enhancing in the areas with greater forest cover and edge density associated with low use of insecticides. The areas composed of different lands with annual croplands surrounding the coffee plantations showed less natural parasitism and parasitoid species diversity. The ecosystem services provided by C. coffeellae and P. coffeae in coffee crops areas require conservation and these species are potential bioproducts for applied biological control programmes.

Kazal-type serine protease inhibitors (KaSPI) play important roles in insect growth, development, digestion, metabolism and immune defence. In this study, based on the transcriptome of Mythimna separata, the cDNA sequence of MsKaSPI with Kazal domain was uploaded to GenBank (MN931651). Spatial and temporal expression analysis showed that MsKaSPI was expressed at different developmental stages and different tissues, and it was induced by 20-hydroxyecdysone in third-instar larvae of M. separata. After 24 h infection by Beauveria bassiana, the expression level of MsKaSPI and the corresponding MsKaSPI content were significantly up-regulated, being 6.42-fold and 1.91-fold to the control group, respectively, while the activities of serine protease, trypsin and chymotrypsin were inhibited. After RNA interference interfered with MsKaSPI for 6 h, the expression decreased by 73.44%, the corresponding content of MsKaSPI protein decreased by 55.66% after 12 h, and the activities of serine protease and trypsin were significantly enhanced. Meanwhile, both the larval and pupal stages of M. separata were prolonged, the weights were reduced and the number of eggs per female decreased by 181. Beauveria bassiana infection also increased the mortality of MsKaSPI-silenced M. separata by 18.96%. These prove MsKaSPI can not only result in slow growth and low fecundity of M. separata by regulating the activity of related protease, but also participate in the resistance to pathogenic fungi by regulating the serine protease inhibitor content and the activities of related serine protease.

Parasitoids are an important group of insects because their species number is among the highest. Multiple studies have addressed the relationships between forest successional age and insect diversity by focusing on herbivorous organisms, but changes in diversity of parasitoids are still poorly known. This work analyses the diversity of parasitoids in tropical forests representing three successional stages. A total of 30 traps were placed, ten in each forest successional stages. We estimated true diversity of Ichneumonidae species and guilds and explored the relationship between their diversity and the abundance of plant species using an Indicator Species Analysis; the relationship between parasitoid species and plant richness and abundance was tested using a Redundancy Analysis. A total of 1522 individuals and 168 morpho-species were captured in four months. Species richness showed no differences; however, parasitoid abundance was higher in young forest, while intermediate forest had the highest true diversity values (¹D) with 71.6 effective species. According to insect guilds, richness, abundance, and diversity were similar in the three vegetation successional stages. This finding may be explained based on the intermediate disturbance hypothesis, which postulates that moderate disturbance levels favor the highest diversity. In conclusion, successional age matters, i.e., diversity is the highest in intermediate stages, while the old forests harbors guilds unique to that successional stage, such as parasitoids of melitophagous larvae of bees. Other successional stages were characterized by a single species of parasitoid, belonging to the genera Eiphosoma and Anomalon, which may indicate altered and preserved forests, respectively.

Phenoloxidase (PO) is a significant biomolecule involved in humoral defence mechanism of invertebrates. Spontaneous melanization of insect haemolymph is the major hinderance for studying PO activity, as haemolymph was collected devoid of phenylthiourea. In the study, no visible melanization was observed in crude serum from the grub of Oryctes rhinoceros up to 30 min of incubation amongst crude haemolymph, diluted haemolymph, crude serum and diluted serum that were subjected to visual observation for spontaneous melanization reaction. Accordingly, crude serum was taken for evaluating PO activity. At the same time, as PO substrates tend to auto-oxidize and provide false optical density value, tris-buffered saline devoid of any substrates were used as blank for PO assays. The ideal wavelength at which maximum PO activity occurred for each substrate, namely, tyrosine, tyramine, dopamine, L-dopa, DL-dopa, catechol, protocatechuic acid and pyrogallol was determined as 407, 410, 429, 465, 403, 466, 428 and 400 nm, respectively. Additionally, time course of oxidation for each phenolic substrate by the serum PO were examined and DL-dopa was identified as the specific substrate for serum PO in the grub of O. rhinoceros. Furthermore, maximum PO activity was observed at 5 min of incubation for 10 mM of DL-dopa that was considered as optimum concentration. The ideal pH and temperature for serum PO activity was observed as 7.5 and 20°C, respectively. These results suggested that standardizing a suitable substrate is an essential prerequisite to evaluate the real PO activity of serum which might significantly fluctuate in each insect model.

Zinc finger protein (Zelda) of Tribolium castaneum (TcZelda) has been showed to play pivotal roles in embryonic development and metamorphosis. However, the regulatory mechanism of TcZelda associated with these physiology processes is unclear. Herein, the developmental expression profile showed that Zelda of T. castaneum was highly expressed in early eggs. Tissue expression profiling revealed that TcZelda was mainly expressed in the larval head and adult ovary of late adults and late larvae. TcZelda knockdown led to a 95% mortality rate in adults. These results suggested that TcZelda is related to the activation of the zygote genome in early embryonic development. Furthermore, 592 differentially expressed genes were identified from the dsZelda treated group. Compared with the control group, altered disjunction (ALD) and AGAP005368-PA (GAP) in the dsZelda group were significantly down-regulated, while TGF-beta, propeptide (TGF) was significantly up-regulated, suggesting that TcZelda may be involved in insect embryonic development. In addition, the expression of Ubx ultrabithorax (UBX), Cx cephalothorax (CX), En engrailed (EN), and two Endocuticle structural glycoprotein sgabd (ABD) genes were significantly down-regulated, suggesting that they may cooperate with TcZelda to regulate the development of insect wings. Additionally, Elongation (ELO), fatty acid synthase (FAS), and fatty acyl-CoA desaturase (FAD) expression was inhibited in dsZelda insects, which could disturb the lipase signaling pathways, thus, disrupting the insect reproductive system and pheromone synthesis. These results may help reveal the function of TcZelda in insects and the role of certain genes in the gene regulatory network and provide new ideas for the prevention and control of T. castaneum.

Termite colony foundation precedes the incipient stage, when the first oviposition cycle takes place, followed by months of reproductive inactivity. The royal couple is supposed to cease oviposition during this period, investing energy to care for the first brood. When a suitable number of alloparents differentiate, egg-laying resumes. Here we followed oviposition dynamics, embryo development and queen/king body changes in laboratory colonies of the major pest species Coptotermes gestroi (Rhinotermitidae) and Cryptotermes brevis (Kalotermitidae) during 9 months. We show that they differ in these oviposition dynamics, as C. gestroi queens displayed an uninterrupted oviposition whereas C. brevis laid a cohort of eggs and ceased oviposition during a 3-month period (lag phase). C. gestroi oviposition dynamic was remarkable and suggests that occurrence of progeny was not a limiting factor, thus queens and kings were able to concomitantly invest energy in reproduction and parental care. These findings contrast those reported for rhinotermitids from temperate areas, and we discuss the likely reasons for such a condition, including endogenous rhythms, avoidance of a high mortality rate of the first progeny and adaptation to the weather conditions of the Neotropical region. Oviposition dynamic in C. brevis resembled those of several termite species, in which the royal couple cease reproduction to care for the first brood. Rearing conditions did not influence oviposition dynamics (egg-laying cycle followed by a lag phase), thus our results on the oviposition of C. gestroi and C. brevis correspond to different reproductive strategies post-foundation adopted by these pest species.

Chemosensory proteins (CSPs) were necessary for insect sensory system to perform important processes such as feeding, mating, spawning, and avoiding natural enemies. However, their functions in non-olfactory organs have been poorly studied. To clarify the function of CSPs in the development of Mythimna separata (Walker) larvae, two CSP genes, MsCSP17 and MsCSP18, were identified from larval integument transcriptome dataset. Both of MsCSP17 and MsCSP18 contained four conserved cysteine sites (C × (6)-C × (18)-C × (2)-C), with a signal peptide at the N-terminal. RT-qPCR analysis showed that MsCSP17 and MsCSP18 have different expression patterns among different developmental stages and tissues. MsCSP17 was highly expressed in 1st-4th instar larvae, and MsCSP18 had high expression in adults. Both genes were expressed highly in larval head, thorax, integument and mandible. Moreover, both of MsCSP17 and MsCSP18 were lowly expressed in larval integuments when larvae molted for 6 h and 9 h from 3rd to 4th instar, but highly at the beginning and end phase during molting. After injection of dsMsCSP17 and dsMsCSP18, the expression levels of two genes decreased significantly, with the body weight of larvae decreased, the mortality increased, and the eclosion rate decreased. It was suggested that MsCSP17 and MsCSP18 contributed to the development of M. separata larvae.