Nonselective oviposition by a fastidious insect: the laboratory host range of the melaleuca gall midge Lophodiplosis trifida (Diptera: Cecidomyiidae)

Invasion by the Australian paperbark, Melaleuca quinquenervia, has degraded large areas of south Florida wetlands. Restoration of these wetlands requires the removal of expansive monocultures of this large tree while simultaneously curtailing its spread. Management strategies developed by federal and state agencies include biological control to halt the spread of this species and to prevent reinfestation of cleared areas. This requires biological agents able to reduce flowering, seed production, and growth while increasing mortality of seedlings and saplings. Two of the three introduced agents (Oxyops vitiosa Pascoe and Boreioglycaspis melaleucae Moore) partially meet these needs but outcomes are not spatially or temporally consistent. Thus, additional agents are needed. The bud-gall fly Fergusonina turneri Taylor, with its mutualistic nematode Fergusobia quinquenerviae Davies and Giblin-Davis, is actively being released but has not established. A fourth promising agent, the gall midge Lophodiplosis trifida Gagné, manifested an extremely narrow host range during laboratory testing. Oviposition was indiscriminant in caged environments. Small, incipient, unilocular galls were initiated on Melaleuca viminalis, but larval development ensued only on M. quinquenervia. The unilocular galls on M. viminalis did not grow and produced no adult flies. As a result, M. viminalis test plants suffered only minor cosmetic damage. Observations from both Australia and Florida attest to the ability of this midge to impede M. quinquenervia growth and kill small plants. Thus, L. trifida is safe to release and will likely contribute to management objectives for control of this pernicious wetland invader.     

Bottom‐up effect of host plants on life‐history characteristics of Aphidoletes aphidimyza feeding on Aphis gossypii

The predatory midge Aphidoletes aphidimyza (Rondani) (Diptera: Cecidomyiidae) is widely used for the control of Aphis spp. in many agricultural systems. We aimed to determine the most suitable host plant for rearing the predatory midges on the prey Aphis gossypii Glover (Hemiptera: Aphididae). Six host plants were selected: cucumber (Cucumis sativus L. cv. Beith Alpha), tomato (Solanum lycopersicum L. cv. Falat111), eggplant (Solanum melongena L. cv. Yummy), pepper (Capsicum annuum L. cv. Bertene) (all Solanaceae), okra [Abelmoschus esculentus (L.) Moensch cv. Clemson Spineless] (Malvaceae), and squash (Cucurbita pepo L. cv. Hybrid rajai) (Cucurbitaceae). Some physical traits (length and density of trichomes) and chemical attributes (nitrogen content) of prey host plants were investigated. The results showed that prey host plants differed significantly in their effect on fitness of the predator. The shortest immature development time (18.07 ± 0.257 days), the longest female adult longevity (7.5 ± 0.18 days), and the highest fecundity (89 eggs/female) of A. aphidimyza were found with squash as prey food. The highest intrinsic rate of increase (0.171 ± 0.009 day^?1) and also the shortest mean generation time (22.4 ± 0.32 days) were also obtained when A. aphidimyza fed on A. gossypii reared on squash. Canonical correlation analysis (CCA) approved the correlation between life‐history traits of A. aphidimyza and characteristics of prey host plants. The suitability of squash for rearing A. aphidimyza can be attributed to the higher nitrogen content, longer trichomes, and relatively high density of trichomes, which provided a better environment for A. gossypii and indirectly favored A. aphidimyza. This study showed that squash is the most suitable host plant for rearing A. aphidimyza feeding on A. gossypii.     

Development and optimisation of a sex pheromone lure for monitoring populations of saddle gall midge,Haplodiplosis marginata

Saddle gall midge, Haplodiplosis marginata (von Roser) (Diptera: Cecidomyiidae), is a sporadic pest of cereals in Northern and Central Europe and is of increasing importance in the UK. Recently, the major component of the sex pheromone produced by adult female H. marginata was reported to be 2‐nonyl butyrate. The importance of absolute configuration on attractiveness, the effects on trap catches of the addition of minor pheromone components, dispenser type, and pheromone loading are described in the development of an optimised pheromone lure with which to trap H. marginata males. In analyses of volatiles collected from virgin female H. marginata by gas chromatography (GC) coupled with electroantennographic recording (EAG) from the antenna of a male H. marginata, two EAG responses were observed. Analyses by coupled GC‐mass spectrometry (MS) indicated these were due to 2‐nonyl butyrate and a trace amount (1%) of 2‐heptyl butyrate. A similar trace amount of 2‐nonanol was detected in GC‐MS analyses but this compound did not elicit an EAG response when the synthetic compound was tested, whereas the other two compounds did. These three compounds were not observed in collections of volatiles made from male H. marginata. The 2‐nonyl butyrate was shown to be the (R)‐enantiomer. In field trapping tests (R)‐2‐nonyl butyrate was at least 10× more attractive to male H. marginata than the racemic compound, and the (S)‐enantiomer was unattractive. Addition of the potential minor components individually or together at the naturally occurring ratios did not increase or reduce the attractiveness of the lure. Polyethylene vials and rubber septa were equally effective as pheromone dispensers, lasting for at least 5 weeks in the field in the UK, although laboratory tests indicated release from the former was more uniform and more likely to last longer in the field. Increasing loading of pheromone in the dispenser increased attractiveness. Traps baited with polyethylene vials containing 0.5 mg of (R)‐2‐nonyl butyrate are recommended for monitoring H. marginata and these are far more sensitive than water or sticky traps currently used for monitoring this pest.     

Insect assemblages on flowering patches of 12 bamboo species

Bamboos are known as long-living monocarpic plants that exhibit synchronous flowering at long intervals. It has been reported that florivory has a critical effect on their seed production in bamboos, especially in small scale flowering patches. In this study, we aimed to determine species composition and life history of florivorous insects in multiple bamboo species. We collected the inflorescences of 12 bamboo species from 15 sites in Japan from 2017 to 2019 and recorded insect assemblages found in the flowers. Five different insect species were observed to feed on the flowers of bamboo species. Among these, the larvae of two Dicraeus species were the most widely observed florivorous insects of the bamboo species. The other insects included the larvae of Cecidomyiidae sp., which was frequently observed on Sasa species, and the other two insects were Epuraea submicrurula, and Dimorphopterus japonicus. These insects were oviposited on the florets during the budding period. In addition, predators and parasitoids were found in the bamboo flowers. Our findings suggest that the bamboos flowers were mainly consumed by dipteran larvae. Insect species composition and frequency varied among bamboo species and sites. Comparing the frequency of the florivorous insects among bamboo flowering patches, including mass flowering patches, in different areas is needed in future studies.     

浙江短角瘿蚊属一新种记述(双翅目:瘿蚊科)

记述采自浙江省的短角瘿蚊1新种:狭短角瘿蚊Anarete angusta Mo et Xu,sp.nov..     

The relationship between morphological traits of the spring wheat spike and oviposition deterrence to orange wheat blossom midge

If morphological traits of a plant cause resistance to an insect pest or are strongly correlated with resistance levels, those traits can be used by plant breeders as phenotypic markers for indirect selection of resistance. To improve our understanding of antixenosis against the orange wheat blossom midge, Sitodiplosis mosellana (Géhin) (Diptera: Cecidomyiidae), expressed as oviposition deterrence in bread wheat, Triticum aestivum L. (Poaceae), 21 morphological traits of the wheat spike were studied in a genetically related wheat population and correlation of the traits with deterrence level was explored. The following traits had larger values in the deterrent parent of the population than the susceptible parent: ligule length, glume length, length of hair inside glume, palea length at post-anthesis stage, length of hair inside lemma, length of hair at spikelet base, inter-spikelet distance, and length of hair at rachis edge at post-anthesis stage. The highest correlation coefficient between mean egg density and a morphological trait of the wheat population was −0.287, which was for inter-spikelet distance. This represented 8% predictability from the point of view of crop breeding and explained one-twelfth of the variation in oviposition deterrence among lines. The morphological traits of bread wheat spikes were not highly correlated to deterrence. Therefore, no promising trait could be recommended for use in breeding programs. Studies of the fine-scale properties of the wheat plant surface, and their interactions with plant surface chemistry, with a greater focus on wheat midge oviposition behavior, may clarify the effect of the morphological traits on oviposition and deterrence.     

Oviposition deterrence in spring wheat, Triticum aestivum, against orange wheat blossom midge, Sitodiplosis mosellana: implications for inheritance of deterrence

Some spring wheat lines are known to be antixenotic to ovipositing orange wheat blossom midge, Sitodiplosis mosellana (Géhin) (Diptera: Cecidomyiidae). The genetic basis of antixenosis, expressed in the plant as oviposition deterrence to S. mosellana , was explored using a population of 92 doubled-haploid wheat lines from a cross between a susceptible parent and a deterrent parent which also had antibiosis resistance. Wheat midge egg densities on wheat spikes were obtained from a standardized laboratory cage test and from the field in 2006 and 2007. Compared to the susceptible parent, egg densities on 55–88% of the lines were reduced by more than half in the laboratory and both years in the field. Twenty-five of the 92 lines were consistently at least as deterrent as the deterrent parent in all three environments. Frequency distribution of egg densities compared to the parents indicated that deterrence was conferred by more than one gene, with complementary interaction among genes. Heritability of deterrence was estimated at 67%, showing that environment had a substantial effect on the phenotypic expression of the trait. Consistently deterrent lines had a larger proportion of eggs laid on the rachis compared to the other lines in all environments, suggesting that the presence of deterrence affects where on the spikelet the females lay their eggs. There was no evidence for linkage between deterrence genes and the antibiosis gene, Sm1 . Oviposition deterrence is a promising means for suppressing wheat midge oviposition in commercial wheat crops; however, the multigenic nature of oviposition deterrence in wheat to S. mosellana and the influence of environment on its expression will provide challenges for incorporating this trait into wheat breeding programs.     

中国垫瘿蚊属研究(双翅目：瘿蚊科)

记述了双翅目瘿蚊科一中国新记录属垫瘿蚊属 Conarete Pritchard 的4 种,其中包括2新种： 短须垫瘿蚊 C. brevipalpa Li et Bu, sp. Nov.（模式产地： 海南尖峰岭）和葫茎垫瘿蚊 C. sicyoidea Li et Bu, sp. Nov.（模式产地：海南尖峰岭）; 另外2种为在中国首次记录的种： 米垫瘿蚊 C. mihijamensis Grover （分布：海南尖峰岭）和印垫瘿蚊 C. indorensis Grover（分布：陕西周至板房子）。文中给出了垫瘿蚊属与近缘的短角瘿蚊属Anarete Haliday的区别特征和中国种类分种检索表。模式标本均保存于南开大学生物学系昆虫标本室。     

Resource partitioning and exploitative competition in stem-galling midges mediated by the host plant

Izeniola obesula Dorchin and Stefaniola defoliata Dorchin (Diptera, Cecidomyiidae) are two cecidomyiid species inducing multichambered galls in young shoots of the salt marsh plant, Suaeda monoica Gmelin (Chenopodiaceae). The purpose of this work was to study the relationship between the two species, which co‐occur in time and space, and may therefore potentially compete for plant resources. Characterization of the resources available to ovipositing females revealed that shoots in apical positions are more vigorous than shoots in basal positions, but that the two species of gall midges react to this variability of resources in different ways, as reflected by the patterns of gall distribution. Izeniola obesula galls were primarily induced in the younger, more rapidly growing shoots, whereas those of S. defoliata were predominantly induced in older, less vigorous shoots. Nevertheless, despite the general partitioning of resources, a certain amount of niche overlap was found, resulting in the occasional induction of an S. defoliata gall proximal to that of I. obesula in the same shoot. Co‐occurrence of the two types of galls in time and space did not have apparent effect on S. defoliata galls, but did have a strong adverse impact on young I. obesula galls, 60% of which were killed without producing adult midges, and the remaining 40% produced a much smaller number of adults. These effects are attributed to asymmetric interspecific competition that is mediated by the plant, resulting from the difference in stem tissues utilized by the larvae of the two species. It is concluded that preponderance of vacant niches, low densities of galls, and small niche overlap between the species do not preclude the occurrence of interspecific exploitative competition in this system, although its role in shaping the populations of the species is limited.