Strain differences in the indian meal moth,Plodia interpunctella,in response to a granulosis virus

Three strains of the Indian Meal Moth,Plodia interpunctella, were compared in terms of their response to a granulosis virus under different environmental conditions. A significant difference in the relative susceptibilities to the virus of the three laboratory strains was established. Evidence of potential trade-offs with resistance was found in overall fecundity, pupal size and mortality at adult emergence. There was however little evidence that a reduction in resource level led to more trade-offs being apparent. No clear relationship was found between resistance to the lethal effects of the virus and susceptibility to the sublethal effects of the virus.     

Cannibalism and the stage-dependent transmission of a viral pathogen of the Indian meal moth, Plodia interpunctella

1. The transmission of an insect pathogen by cannibalism was studied by a series of choice and no-choice experiments.
2. Infection of Plodia interpunctella larvae with a granulosis virus occurred through cannibalism of infected larvae.
3. Depending on the larval instars of the cannibal and the victim relative to each other, preferential cannibalism of both infected and healthy larvae was observed.
4. Larvae cannibalise healthy, less vulnerable larvae preferentially, but it is argued that there is no evidence that they are avoiding infection.
5. The victim cannibalised can be explained as a balance between the reduced risk of injury and the ease of cannibalism of moribund infected individuals on the one hand and the greater food resource value of healthy individuals on the other.
6. The implications for the insect population dynamics of the transmission of the pathogen via cannibalism and the effective removal of infective particles through cannibalism by immune stages are discussed.     

Behavioral and reproductive effects of ultrasound on the Indian meal moth, Plodia interpunctella

The daily activity patterns of adult movement, female calling, and mating of the Indian meal moth, Plodia interpunctella (Hübner) (Lepidoptera: Pyralidae), were examined both in the absence and presence of ultrasound. Moths were exposed to ultrasound from a commercial ultrasonic device (Cix 0600) that produces constant sound patterns, and from a device developed at Kansas State University (KSU device) that produces random sound patterns. Daily activity patterns of adult movement, female calling, and mating followed a similar trend in the absence or presence of ultrasound. Female calling and mating, both in the absence and presence of ultrasound, primarily occurred during scotophase (21.00–07.00 hours). Ultrasound from the two devices significantly reduced the frequency of female calling and mating relative to unexposed moths. Consequently, the number of spermatophores transferred by males to females and egg production were lower in females exposed to ultrasound compared with unexposed females. In the absence of ultrasound, female P. interpunctella mated 2.9 times, resulting in 2.8 spermatophores/female. In the presence of ultrasound from the Cix 0600 device, a female mated 2.1 times and had 1.7 spermatophores. Corresponding values for the KSU device were 1.9 and 1.4, respectively. In the absence of ultrasound, 78% of the matings lasted 30–90 min, whereas in the presence of ultrasound 45–58% of the matings lasted either less than 30 min or more than 90 min. Moths exposed to ultrasound laid 96–130 eggs female^?1 compared with 229 eggs female^?1 for unexposed moths. Ultrasound did not affect the pre‐oviposition period and adult longevity of P. interpunctella.     

中国印度谷螟性信息素次级组份的研究

印度谷螟是我国危害性较严重的仓储害虫之一,食性很广,几乎危害每一种植物性仓储物.印度谷螟雌虫性信息素主要成份顺9,反12-十四碳二烯醇醋酸酯(TDA)早已被鉴定,并利用TDA单一组份诱捕印度谷螟雄蛾也较为有效,但该虫的完整信息素系统尚不清楚.本研究采用单个雌蛾性信息素腺体抽提技术,利用毛细管气相色谱GC保留时间定性方法和气质联用GC-MS分析鉴定技术,从印度谷螟雌虫腺体提取物中鉴定了顺9,反12-十四碳二烯醇醋酸酯(A),顺9,反12-十四碳二烯醇(B),顺9,反12-十四碳二烯醛(C)和顺9-十四碳醋酸醋(D)4种主要信息素成份,其比例为A∶B∶C∶D=100∶22∶12∶9.风洞试验结果表明,以该4种主要成分按A∶B∶C∶D=8∶2∶1∶0.8比例配制成的诱芯,其引诱雄蛾的活性接近于雌蛾腺体提取物.     

Evidence for strong intralocus sexual conflict in the Indian meal moth, Plodia interpunctella

Males and females share a genome and express many shared phenotypic traits, which are often selected in opposite directions. This generates intralocus sexual conflict that may constrain trait evolution by preventing the sexes from reaching their optimal phenotype. Furthermore, if present across multiple loci, intralocus sexual conflict can result in a gender load that may diminish the benefits of sexual selection and help maintain genetic variation for fitness. Despite the importance of intralocus sexual conflict, surprisingly few empirical studies conclusively demonstrate its operation. We show that the pattern of multivariate selection acting on three sexually dimorphic life-history traits (development time, body size, and longevity) in the Indian meal moth, Plodia interpunctella, is opposing for the sexes. Moreover, we combined our estimates of selection with the additive genetic variance-covariance matrix (G) to predict the evolutionary response of the life-history traits in the sexes and showed that the angle between the vector of responses and the vector of sexually antagonistic selection was almost orthogonal at 84.70°. Thus, G biases the predicted response of life-history traits in the sexes away from the direction of sexually antagonistic selection, confirming the presence of strong intralocus sexual conflict in this species. Despite this, sexual dimorphism has evolved in all of the life-history traits examined suggesting that mechanism(s) have evolved to resolve this conflict and allow the sexes to reach their life-history optima. We argue that intralocus sexual conflict is likely to play an important role in the evolution of divergent life-history strategies between the sexes in this species.     

Comparative virulence of Nosema plodiae and Nosema heterosporum in the Indian meal moth, Plodia interpunctella

When larvae of the Indian meal moth, Plodia interpunctella, were fed diets containing spores of Nosema plodiae, the number that survived to the adult stage decreased and the rate of adult emergence was retarded as the concentration of spores was increased; all surviving adults were infected. Also, when larvae were reared on diets containing spores of Nosema heterosporum, the number that survived to the adult stage decreased as the concentration of spores was increased; however, no relationship was apparent between concentration of spores and the rate of adult emergence. The LC₅₀'s of N. plodiae and N. heterosporum were 8.09 × 10⁶ and 4.52 × 10³ spores/g diet, respectively, which confirmed preliminary observations regarding the relative virulence of the two species of Nosema to Indian meal moth larvae.     

Toxicity of parasporal crystals of Bacillus thuringiensis to the Indian meal moth, Plodia interpunctella.

Toxicity of Bacillus thuringiensis parasporal crystals to the Indian meal moth, Plodia interpunctella, is described. The numbers of insects killed were in relation to crystal dry weight. Mortality was determined by comparing adult emergence in diets treated with crystals to emergence in untreated diets. There was only a 30% survival at an application of 0.414 microgram/cm2, and the mean 50% lethal concentration value was found to be 0.299 microgram/cm2. The use of emergence data has provided a reliable and reproducible bioassay for comparing relative toxicities of crystals, spores, and other cellular components to this economically important insect.     

Toxicity of parasporal crystals of Bacillus thuringiensis to the Indian meal moth, Plodia interpunctella.

Toxicity of Bacillus thuringiensis parasporal crystals to the Indian meal moth, Plodia interpunctella, is described. The numbers of insects killed were in relation to crystal dry weight. Mortality was determined by comparing adult emergence in diets treated with crystals to emergence in untreated diets. There was only a 30% survival at an application of 0.414 microgram/cm2, and the mean 50% lethal concentration value was found to be 0.299 microgram/cm2. The use of emergence data has provided a reliable and reproducible bioassay for comparing relative toxicities of crystals, spores, and other cellular components to this economically important insect.     

Isolation and purification of a granulosis virus from infected larvae of the Indian meal moth, Plodia interpunctella.

A procedure was developed for purification of a granulosis virus inclusion body produced in vivo in the Indian meal moth, Plodia interpunctella (Hübner). Purification was accomplished by differential centrifugation, treatment with sodium deoxycholate, and velocity sedimentation in sucrose gradients. The adequacy of the procedure was confirmed by mixing experiments in which uninfected, radioactively labeled larvae were mixed with infected, unlabeled larvae. After purification, the virus was shown to be free of host tissue, to retain its physical integrity, and to be highly infectious per os. Preparations of purified virus consisted of homogeneous populations of intact inclusion bodies (210 by 380 nm) whose buoyant density was 1.271 g/cm3 when centrifuged to equilibrium in sucrose gradients. Electron microscopy of thin-sectioned virus or of virus sequentially disrupted on electron microscope grids demonstrated three components: protein matrix, envelope, and nucleocapsid.     

Isolation and purification of a granulosis virus from infected larvae of the Indian meal moth, Plodia interpunctella.

A procedure was developed for purification of a granulosis virus inclusion body produced in vivo in the Indian meal moth, Plodia interpunctella (Hübner). Purification was accomplished by differential centrifugation, treatment with sodium deoxycholate, and velocity sedimentation in sucrose gradients. The adequacy of the procedure was confirmed by mixing experiments in which uninfected, radioactively labeled larvae were mixed with infected, unlabeled larvae. After purification, the virus was shown to be free of host tissue, to retain its physical integrity, and to be highly infectious per os. Preparations of purified virus consisted of homogeneous populations of intact inclusion bodies (210 by 380 nm) whose buoyant density was 1.271 g/cm3 when centrifuged to equilibrium in sucrose gradients. Electron microscopy of thin-sectioned virus or of virus sequentially disrupted on electron microscope grids demonstrated three components: protein matrix, envelope, and nucleocapsid.     

Characterization of polymorphic microsatellite markers in the Indian meal moth,Plodia interpunctella (Hübner)

The Indian meal moth, Plodia interpunctella (Hübner), is a serious and widespread pest of stored food commodities worldwide. Studies on the population genetics and breeding structure of P. interpunctella are lacking. Understanding the breeding structure of this pest has implications for its management. Fifteen microsatellite loci were isolated, cloned and characterized using an enrichment method. Forty individuals from six subpopulations were tested for polymorphism. Nine loci were found to be polymorphic. The number of alleles varied from three to six per locus.     

Responses to stepwise photoperiodic changes for the larval diapause of the Indian meal moth Plodia interpunctella

Abstract The Indian meal moth Plodia interpunctella Hübner (Lepidoptera: Pyralidae) diapauses as a last‐instar (fifth) larva. At 30 °C, no larvae enter diapause under any photoperiodic conditions; at 25 °C, the photoperiodic response curve is a long‐day type with a critical length of approximately 13 h light; at 20 °C, diapause is induced moderately even under long days (> 13 h). Cumulative effects of short days or long days on diapause induction are determined by alternate, stepwise and gradually changing regimes of photoperiod at 25 °C. When the larvae are repeatedly exposed to LD 16 : 8 h and LD 12 : 12 h photoperiods every other day, the incidence of diapause is 37%. When the larvae are placed under an LD 16 : 8 h photoperiod for 2 days and then under an LD 12 : 12 h photoperiod for 1 day, it is 38 %. Exposure to an LD 16 : 8 h photoperiod for 1 day and then to an LD 12 : 12 h photoperiod for 2 days induces only 15% diapause. This may indicate that the photoperiodic information is not accumulated in a simple fashion despite the generally accepted hypothesis (i.e. photoperiodic counter). Larvae exposed to an LD 16 : 8 h photoperiod for 5 days after oviposition express a very high incidence of diapause even under short days between an LD 2 : 22 h and LD 12 : 12 h photoperiod. After 10 days exposure to an LD 16 : 8 h photoperiod, however, the short day does not induce diapause strongly. On the other hand, an LD 12 : 12 h photoperiod in the early larval life is highly effective in the induction of diapause. A gradual increase or decrease of photoperiod (2 min day^?1) shows that the direction of photoperiodic change does not affect the diapause determination.     

Sex‐biased gene expression during the adult stage of the Indian meal moth Plodia interpunctella

Sexual dimorphisms are primary regulated by sex‐biased gene expression. In the present study, using real‐time polymerase chain reaction, we determined the expression profiles of nine genes associated with development, metabolism, stress, and defense throughout adulthood of the Indian meal moth Plodia interpunctella, a global pest of stored food products. Most genes were differentially expressed in a sex‐biased manner during the adult lifespan of the moth. Expression of the heat shock protein genes hsp25 and hsp90 and the antioxidant gene thioredoxin peroxidase (Tpx) was highly female biased, whereas the expression of a gene related to host development (ecdysone receptor [EcR]) and two genes associated with immunity (β‐glycan recognition protein [βgrp] and prophenoloxidase [ProPO]) was male biased. In contrast, the expression of hsp70, glucose‐regulated protein 78 (grp78) and ultraspiracle (USP) was not sex biased. The results of the present study provide important insights into the role of sex‐biased genes in the physiology and behavior of P. interpunctella.     

Effects of resource quality on the population dynamics of the Indian meal moth Plodia interpunctella and its granulovirus

Although the Plodia interpunctella-granulovirus system is one of the most studied models for insect-pathogen interactions, there are relatively few precise data on the dynamics of the virus in coexisting populations of these two organisms. Previous work has suggested that resource quality, in terms of the diet supplied to P. interpunctella, has a strong effect on the population dynamics of host and pathogen. Here we investigate the impact of resource-dependent host patterns of abundance on pathogen dynamics and prevalence. In the laboratory, three populations of P. interpunctella feeding on a good quality food and infected with a granulovirus were compared with three populations also infected with a granulovirus but feeding on poor quality food. Populations feeding on good quality food produced larger adult moths, and had greater numbers of adult moths, healthy larvae, and virus-infected larvae. A higher proportion of larvae in these good quality populations were infected with virus, and adult moths exhibited cyclic fluctuations in abundance, unlike those on poor quality food. This cyclic behaviour was shown to be associated with cycles in the age structure of the larval population. Previous theoretical work suggests that these cycles may result from asymmetric competition between young and old larvae. Cyclic fluctuations in the proportion of infected larvae, that occurred on good, but not on poor quality food, were also shown to be related to cycles in the age structure of the larval population.     

Reidentification of the female sex pheromone of the Indian meal moth, Plodia interpunctella: evidence for a four-component pheromone blend

Pheromone gland extracts from calling female Plodia interpunctella contained at least seven compounds that consistently elicited electroantennographic responses from male antennae upon gas chromatographic analysis. Three of these compounds were found to be the previously identified gland constituents, i.e., (Z,E)-9,12-tetradecadienyl acetate (Z9,E12-14:OAc), (Z,E)-9,12-tetradecadienal (Z9,E12-14:Ald) and (Z,E)-9,12-tetradecadienol (Z9,E12-14:OH). A fourth EAD-active compound was identified as (Z)-9-tetradecenyl acetate (Z9-14:OAc). The homologue (Z)-11-hexadecenyl acetate (Z11-16:OAc) was also identified in the extracts, but showed no EAD activity. The identity of all five compounds was confirmed by comparison of GC retention times and mass spectra with those of synthetic standards. In flight tunnel tests there were no significant differences in response of male P. interpunctella to the bait containing all four EAD-active compounds and the responses to female gland extacts. A behavioural assay of different two-compound blends in the flight tunnel showed that only addition of the corresponding aldehyde to the major pheromone component Z9,E12-14:OAc raised the male response. A subtractive assay, however, revealed that the exclusion of any of the compounds from the complete four-compound blend reduced its activity significantly. We thus conclude that the female-produced sex pheromone of P. interpunctella consists of at least four components, i.e., Z9,E12-14:OAc, Z9,E12-14:Ald, Z9,E12-14:OH and Z9-14:OAc.In a field trapping test performed in a storage facility, the four-component blend attracted significantly more males of P. interpunctella than traps baited with Z9,E12-14:OAc alone. In contrast, the highest number of Ephestia kuehniella males was found in the traps baited with this major component, suggesting that the secondary pheromone components contribute to the species specificity of the blend.     

The role of the main photophase on dark-time measurement used for diapause determination in the Indian meal moth, Plodia interpunctella

Abstract.  The Indian meal moth Plodia interpunctella Hubner (Lepidoptera: Pyralidae) measures night length and enters diapause as a last-instar larva. To examine the role of photophase on dark-time measurement, the main LD 7 : 17 h photoperiod is disrupted by various lengths of darkness at 25 °C. When the light phase is not disrupted, the incidence of diapause is 76%. As the dark pulse disrupting a 7-h photophase becomes longer, the incidence of diapause decreases. To detect the dynamic kinetics of the time-measuring process, the main scotophase of 17 h is scanned by a 2-h light pulse. When the dark pulse in a 7-h photophase is fixed at 1 h after dawn and its duration is varied systematically from 1 to 3 h, or when the end of the dark pulse is fixed at 1 h before dusk, diapause is prevented completely by a 2-h light pulse inserted in the middle of 17-h darkness. These results are compared with those of a single night interruption of a 17-h scotophase with a 2-h light pulse but with an intact 7-h photophase. The disruption of a 7-h photophase by a dark pulse shifts the descending and ascending slopes of the response curve to some extent toward dawn and dusk, respectively, indicating that the dark pulse tends to shorten the critical length of dark time for diapause induction. When the main photophase (7 h) is interrupted by a 1-h dark pulse at 3–4 h after dawn, the 2-h scanning light pulse in the main scotophase (17 h) appears to act effectively as a dusk signal in the early scotophase. However, those in the mid- and late scotophase do not define the critical night length from dusk as sharply as for the critical night length from a 2-h light pulse to dawn. The results indicate the importance of photophase in the dark-time measurement.     

Effects of a fertility-reducing baculovirus on sperm numbers and sizes in the Indian Meal Moth, Plodia interpunctella

1. A dose-dependent decrease in male fertility occurs in the Indian Meal Moth, Plodia interpunctella , when sub-lethally infected with granulovirus during the larval stage.
2. Here, the causes for this decline are investigated by examining eupyrene and apyrene sperm numbers and sizes produced by males across four levels of viral challenge.
3. The results could not explain how reduced male fertility is caused in this host–pathogen interaction. While a reduction in both eupyrene and apyrene sperm numbers from all virus-treated males was found, this was not significant and neither was there a difference in sperm lengths across the four treatments. There were also no differences in the variances of sperm numbers or lengths between the doses, and no associations between sperm numbers or lengths and body size were found.
4. A significant correlation between eupyrene and apyrene numbers was found, but this was independent of dose. Significant between-male variance in apyrene sperm lengths was found, indicating that individual males differ in the range of apyrene sperm sizes they produce.
5. It is suggested that further intracellular and behavioural study is needed to identify the causes of the granulovirus-induced reduction in fertility of P. interpunctella .     

Long‐term rearing affects pheromone‐mediated flight behaviour of the Indian meal moth,Plodia interpunctella

The pest Plodia interpunctella (Hübner) is reared in many research laboratories. In a culture established in 1996, attraction of males to the female‐produced sex pheromone in flight tunnel assays gradually decreased after ≈15 years of rearing. A new culture was established to enable comparison with the old culture regarding traits associated with mate finding. Female calling activity, pheromone titre and male antennal response to pheromone components did not differ between cultures. In contrast, very few males from the old culture reached the pheromone source in flight tunnel assays compared with 61%–81% of males from the other culture. Our results highlight the importance of maintaining viable insect cultures for research purposes and suggest frequent evaluation of traits involved in chemical communication in such cultures to ensure reliable results in experiments.