Beautiful Bugs,Bothersome Bugs,and FUN Bugs: Examining Human Interactions with Insects and Other Arthropods

Because the ostensible majority of incidental human–insect (and other arthropods) interactions are negative, any interest in non-pretty “bugs” appears to be inherently demotivated. Three complementary studies explored US college students’ perceptions, knowledge, and experiences of insects to better understand folk classifications and to identify potentially new ways to present them to motivate human interest. Study 1, an open-ended survey (n = 236), found that knowledge of insects is limited to a mean of 13 insects. Of these 13 insects, most were also dichotomized as liked (beautiful bugs) or disliked (bothersome bugs). The second study, using semi-structured interviews (n = 60), revealed similar categories as found in the first study, providing further details about positive and negative perceptions of, attitudes to, and types of experiences people have with, insects and other closely related arthropods. The last study (n = 200) used a paired forced-choice scale with 10 silhouettes of insects and related arthropods to replicate and expand the findings from the first two studies. This study tested whether respondents would report interest in novel and unknown arthropods over commonly known and preferred ones. The results indicate little knowledge of the diversity of insects among a young, elite, middle-class sample of college students and the existence of two robust but small folk categories of insects/arthropods (beautiful, bothersome). Results from the third study indicated there is a group of potentially fascinating unfamiliar (FUN) insects/arthropods/bugs that could evoke interest if people were simply exposed to them. Implications for informal recreation and educational programming and a research agenda are presented.     

Mechanisms of resistance to pyrethroid insecticides

In the 10 years or so since the photostable pyrethroid insecticides such as permethrin and fenvolerate were introduced, this family of compounds has become widely used to control agricultural pests, and finds increasing usage to control arthropods of medical and veterinary importance. The synthetic pyrethroids offer many advantages for veterinary and public health use, particularly their selectivity, high toxicity to insects, and relative lack of chronic effects. They are also inherently stable, and so have become widely used as residual sprays on house walls to control insects in the domestic environment. But as with other classes of insecticides such as organochlorines, organophosphotes and carbamates, resistance to pyrethroids is now increasingly reported. In this article, Tom Miller explains the principle mechanisms of resistance to pyrethroids, using the North American horn fly (Haematobia irritans) as an example now showing many common resistance traits.     

A food-web approach to economic thresholds: A sequence of pests/predaceous arthropods on California cotton

The value of an adequate food base for predaceous arthropods as provided byTetranychus is relevant for the development of economic thresholds for this group and also for pests that occur later in the season. A higher predaceous potential was reflected in greater levels ofGeocoris and ofOrius on untreated plants with abundant food, as compared with lower predator numbers on insecticide-treated plants having lower food levels. The higher numbers ofGeocoris andOrius were significant because they persisted through July–August. In the San Joaquin Valley, an increase in predators during this period is highly beneficial, becauseLygus and lepidopterous worms may damage cotton at this time.Policy guidelines on effects from chemicals on arthropods need re-evaluation. The assessment of disruptive effects of chemicals must include their impact on the arthropods that constitute the principal sources of food for predaceous arthropods. The indirect effect of chemicals against beneficial-predaceous insects via disruption of their food chain is highly significant because a considerably longer time-interval is required to replenish the food supply, than is needed for beneficial-predaceous adults to reinvade a field.Results from this study support our contention that at least four components must be considered seasonally in developing economic thresholds for pest management programs: 1) the plants. 2) the complex of key pests, 3) the complex of beneficial arthropods, and 4) sources of food in the form of minor «pests» required to support significant numbers of predaceous arthropods in agricultural crops.     

Influence of native ants on arthropod communities in a vineyard

• 1 Ants can have a range of effects on arthropods in crops, including suppressing herbivores such as caterpillars. However, ants can also increase hemipteran densities while reducing natural enemy numbers. In vineyard ecosystem, the effects of native ants and their interactions with other arthropods are poorly understood.
• 2 An ant‐exclusion experiment was designed to test the impact of native ants on both canopy and ground arthropods concurrently. The potential influence of ants on predation and parasitism of light brown apple moth (LBAM) eggs, a grape pest, was also examined. Adult grapevine scale insects and earwigs under bark were counted after a season of ant‐exclusion.
• 3 Among 23 ground ant species collected, six were found to forage in the canopy, with two Iridomyrmex species being the most commonly encountered.
• 4 There was no difference in the abundance of most arthropod orders and feeding groups between ant‐excluded and control vines, although ground spiders were more abundant under ant‐excluded vines, despite increased ground ant foraging pressure. LBAM egg parasitism and predation were low and probably affected by weather and other arthropods. Ant exclusion did not reduce survival of scale insects, although the distribution and abundance of scale insects were negatively associated with earwigs.
• 5 In conclusion, native ants did not consistently suppress arthropod assemblages, including natural enemies, and they did not promote the survival of scale insects. Interactions among native ant species within a vineyard might minimize their effects on other arthropods, although this needs further study.

     

An assessment of the probability of secondary poisoning of forest insectivores following an aerial 1080 possum control operation

Assays for the toxin sodium monofluoroacetate (compound 1080) were undertaken on arthropods collected from toxic baits after a brushtail possum (Trichosorus vulpecula) control operation in Nothofagus forest in central North Island, New Zealand. The 1080 concentrations measured (mean 57 mu g per g, max 130 mu g per g) are considerably higher than those reported by other researchers who collected arthropods randomly after control operations. These data, together with published information on sensitivities to 1080, as well as diet and consumption rates, were used to calculate the median lethal doses of arthropods that have fed on 1080 baits for a number of vertebrate insectivores found in Nothofagus forest. The results indicate small insectivores that feed on, or close to, the ground (e.g., tomtit Petroica macrocephala, robin P. australis, hedge sparrow Prunella modularis, and the short-tailed bat Mystacina tuberculata) may be vulnerable to secondary poisoning. For instance, a tomtit will receive the median lethal dose of 1080 from 1.32 g (i.e., 14.7% of its daily food intake) of arthropods containing 57 mu g per g of 1080. Because of their greater sensitivity to 1080 poisoning, bats are at much greater risk; a short-tailed bat will receive the median lethal dose of 1080 from as little as 0.04 g (0.7% of its daily food intake) of arthropods containing 57 mu g per g of 1080.     

Health status and biological damage to tree leaves in green areas of Syktyvkar

The health status and biological damage to trees in green areas of Syktyvkar are studied. Birch and poplar are dominant trees among 103 species. The health status of trees is generally evaluated as good. The leaf damage by sucking and gnawing insects is increased, and the activity of leaf-mining and gall-forming insects is reduced. We identified 56 species of herbivorous arthropods, ten of which are new for the Komi Republic.     

Cantharidin world in nature: a concealed arthropod assemblage with interactions via the terpenoid cantharidin

Cantharidin is produced by beetles of only two families, the Meloidae and the Oedemeridae. This substance is a defensive terpenoid that is toxic to the enemies of the beetles. Cantharidin also attracts other groups of insects and has been used as a bait to trap them. Cantharidin‐baited traps deployed in central Japan captured coleopterans (Anthicidae, Endomychidae, Pyrochroidae, and Scarabaeidae), dipterans (Ceratopogonidae), hymenopterans (Formicidae), and harvestmen (Podoctidae). The seasonal occurrences of these arthropods, their sex ratios, known feeding choices, and mating habits suggest three possible underlying reasons for the attractancy of cantharidin: (i) it is accumulated as a defense against enemies and sometimes for transfer from males to females as a nuptial gift; (ii) it is used as a chemical cue in food searching; and (iii) it is used as an aggregation pheromone by mature arthropod individuals. The group of canthariphilous arthropods we describe represents a cryptic ecological assemblage with rare chemical networking among apparently unrelated species.     

Emerging aquatic insects as predators in terrestrial systems across a gradient of stream temperature in North and South America

1. Empirical and theoretical research over the past decade has demonstrated the widespread importance of aquatic subsidies to terrestrial food webs. In particular, adult aquatic insects that emerge from streams and lakes are prey for terrestrial predators. While variation in the magnitude of this subsidy is clearly important, the potential top‐down effects of the predatory adults of some aquatic insects in terrestrial food webs are largely unknown. 2. I used published data on benthic insect density (as a proxy for emergence) in North and South America to explore how the proportion of benthic insects that are predatory as adults varies across a gradient of mean annual stream temperature. 3. The proportion of benthic insects that are predatory as adults varied widely across sites (0–12% by abundance; 0–86% by biomass). There was a positive relationship between mean annual stream temperature and the proportion of predatory adults across all sites, driven largely by the greater abundance/biomass of predatory taxa (e.g. odonates), relative to non‐predators (e.g. midges, mayflies, caddisflies), in tropical than in temperate streams. 4. The ‘trophic structure’ (i.e. the proportion of predators) of emerging adult aquatic insects is an understudied source of variation in aquatic–terrestrial interactions. Incorporation of trophic structure in future studies is needed to understand how future modification of fresh waters may affect adjacent terrestrial food webs through both bottom‐up and top‐down effects.     

Effects of the emerald ash borer invasion on the community composition of arthropods associated with ash tree boles in Maryland,U.S.A.

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Does corazonin signal nutritional stress in insects?

The undecapeptide corazonin, initially discovered from the American cockroach as a strong cardioaccelerator, is now known to be ubiquitously present in arthropods, although it is absent from some species, notably Coleoptera. The structure of its precursor is similar to the GnRH precursor, while it acts through a receptor related to the GnRH receptor; corazonin thus appears to be an arthropod homolog of GnRH. It is produced by neuroendocrine cells in the brain, as well as interneurons in the ventral nerve cord. These two cell types are generally present in insects; in most species there are also other neurons producing corazonin. Its function in insects has remained obscure; its cardioacceleratory effects are limited to a few cockroach species, while in other species different physiological effects have been described. Most spectacularly it induces changes associated with the gregarious phase in migratory locusts and in the silkworm it reduces the size of the cocoon formed. Corazonin is able to induce ecdysis in two moth species, however locusts and flies in which the corazonin gene is no longer expressed, ecdyse normally and, hence, it is not clear whether corazonin is essential for ecdysis. As the corazonin neuroendocrine cells in the brain express receptors for two midgut peptides, it seems likely that their activity is modulated by the midgut endocrine cells. I propose that in insects corazonin might be released under conditions of nutritional stress, which can explain several of the observed physiological effects of this neurohormone.     

Food webs obscure the strength of plant diversity effects on primary productivity

Plant diversity experiments generally find that increased diversity causes increased productivity; however, primary productivity is typically measured in the presence of a diverse food web, including pathogens, mutualists and herbivores. If food web impacts on productivity vary with plant diversity, as predicted by both theoretical and empirical studies, estimates of the effect of plant diversity on productivity may be biased. We experimentally removed arthropods, foliar fungi and soil fungi from the longest‐running plant diversity experiment. We found that fungi and arthropods removed a constant, large proportion of biomass leading to a greater reduction of total biomass in high diversity plots. As a result, the effect of diversity on measured plant productivity was much higher in the absence of fungi and arthropods. Thus, diversity increases productivity more than reported in previous studies that did not control for the effects of heterotrophic consumption.     

Sexual reproduction of insects is regulated by cytoplasmic bacteria

The effects have been considered that the intracellular symbiotic alpha-proteobacteria Wolbachia pipientis induces in its hosts, such as insects and other arthropods: cytoplasmic incompatibility upon mating, feminization, parthenogenesis, and androcide. Specific features of the bacterium genome and possible mechanisms of its action on hosts are discussed.     

Stable isotope methods in biological and ecological studies of arthropods

This is an eclectic review and analysis of contemporary and promising stable isotope methodologies to study the biology and ecology of arthropods. It is augmented with literature from other disciplines, indicative of the potential for knowledge transfer. It is demonstrated that stable isotopes can be used to understand fundamental processes in the biology and ecology of arthropods, which range from nutrition and resource allocation to dispersal, food‐web structure, predation, etc. It is concluded that falling costs and reduced complexity of isotope analysis, besides the emergence of new analytical methods, are likely to improve access to isotope technology for arthropod studies still further. Stable isotopes pose no environmental threat and do not change the chemistry or biology of the target organism or system. These therefore represent ideal tracers for field and ecophysiological studies, thereby avoiding reductionist experimentation and encouraging more holistic approaches. Considering (i) the ease with which insects and other arthropods can be marked, (ii) minimal impact of the label on their behaviour, physiology, and ecology, and (iii) environmental safety, we advocate more widespread application of stable isotope technology in arthropod studies and present a variety of potential uses.     

Can biodiversity hotspots protect more than tropical forest plants and vertebrates?

Conservation International's biodiversity hotspots are areas of high vascular plant endemism combined with high levels of habitat destruction and land use change. Although such hotspots have also been shown to be centres for terrestrial vertebrate endemism, much less is known about how well these areas function as hotspots for other less well‐studied groups, including the hyperdiverse arthropods, other invertebrates and fungi. Because there is a close evolutionary and ecological relationship between insects and plants, we suggest that the potential role of plants as umbrella species for herbivorous insects, potentially herbivorous fungi and nematodes, and parasitic insects should be explored. Finally, we reflect on the increasing social, economic, human conflict and governance issues and the impacts of increasing land use change and global climate change that threaten the biodiversity hotspot system.     

Effects of carrion decomposition on litter arthropod assemblages

1. Many organisms contribute to the decomposition of carrion. For arthropods, many studies focus on the necrophagous community, those directly consuming carrion.
2. Necrophagous arthropods use carrion as a shelter or food source. Therefore, carrion generally increases the abundance and biodiversity of necrophagous species. However, it is unclear if carrion has similar effects on detrital communities.
3. This study examines changes in community structure and composition of necrophilous and detrital communities over the course of decomposition.
4. Five pig head carrion were placed at least 7 m apart under cages in temperate mixed forest. Leaf litter was sampled 0 m, 1.5 m, and 3 m from each carrion weekly during summer, and monthly during autumn, until the first frost. Arthropods were extracted from leaf litter by using Berlese funnels.
5. At the carrion site, necrophagous insects increased in abundance, species richness, and Shannon diversity during decomposition, and all decreased after dry decay.
6. Detritus arthropods displayed a sharp increase in abundance during advanced decay, decreasing during dry decay, and a general increase over time for species richness and diversity.
7. In conclusion, carrion can influence the surrounding, non-necrophagous arthropod community, highlighting the need to investigate carrion effects beyond typical necrophagous species to have a more holistic understanding of carrion ecology.

     

Aquatic Terrestrial Linkages Along a Braided-River: Riparian Arthropods Feeding on Aquatic Insects

Rivers can provide important sources of energy for riparian biota. Stable isotope analysis (δ¹³C, δ¹⁵N) together with linear mixing models, were used to quantify the importance of aquatic insects as a food source for a riparian arthropod assemblage inhabiting the shore of the braided Tagliamento River (NE Italy). Proportional aquatic prey contributions to riparian arthropod diets differed considerable among taxa. Carabid beetles of the genus Bembidion and Nebria picicornis fed entirely on aquatic insects. Aquatic insects made up 80% of the diet of the dominant staphylinid beetle Paederidus rubrothoracicus. The diets of the dominant lycosid spiders Arctosa cinerea and Pardosa wagleri consisted of 56 and 48% aquatic insects, respectively. In contrast, the ant Manica rubida fed mainly on terrestrial sources. The proportion of aquatic insects in the diet of lycosid spiders changed seasonally, being related to the seasonal abundance of lycosid spiders along the stream edge. The degree of spatial and seasonal aggregation of riparian arthropods at the river edge coincided with their proportional use of aquatic subsidies. The results suggest that predation by riparian arthropods is a quantitatively important process in the transfer of aquatic secondary production to the riparian food web.     

Insect diversity: facts,fiction and speculation*

Biologists are still trying to grasp the global dimensions of the phylum Arthropoda and its major class the Insecta, in spite of the fact that over a million species of arthropods have been described. The canopy of rain forest trees is believed by many to hold the key to the immense diversity of insects. In recent years the use of knock-down insecticides to sample insects from rain forest canopy has revealed information on the canopy's arthropod inhabitants and community structure. The sampling techniques involved are outlined and data reviewed on taxonomic and guild structure, species abundance, body size and biomass of insects, and the faunal similarity of trees. Calculations by Erwin (1982), based on knock-down insecticide studies of the beetle fauna of one species of Central American tree, suggest there may be 30 million species of tropical forest arthropods. Reanalysis of these calculations, using additional data, produces a range of possible estimates from about 10 to 80 million. The unknown range of plant host-specificities of tropical insects is the main weakness of this method of calculation. Assessment of the faunal importance of the canopy in relation to that of other rain forest biotopes requires comparative quantitative studies. The preliminary results of one such simple study suggest that over 42 million arthropods may be found in a hectare of Seram rain forest (at the time of study), and that 70% occur in the soil and leaf litter and 14% in the canopy. They also suggest that Collembola and Acarina are the dominant groups in this hectare, and that there are as many ants as all the other insects (excluding Collembola).     

Wolbachia infection frequencies in insects: evidence of a global equilibrium?

Wolbachia are a group of cytoplasmically inherited bacteria that cause reproduction alterations in arthropods, including parthenogenesis, reproductive incompatibility, feminization of genetic males and male killing. Previous general surveys of insects in Panama and Britain found Wolbachia to be common, occurring in 16-22% of species. Here, using similar polymerase chain reaction methods, we report that 19.3% of a sample of temperate North American insects are infected with Wolbachia, a frequency strikingly similar to frequencies found in two other studies in widely separated locales. The results may indicate a widespread equilibrium of Wolbachia infection frequencies in insects whose maintenance remains to be explained. Alternatively, Wolbachia may be increasing in global insect communities. Within each of the three geographic regions surveyed, Hymenoptera are more frequently infected with A group Wolbachia and Lepidoptera more frequently infected with B group Wolbachia.     

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Alien arthropod predators and parasitoids: interactions with the environment

Many species of entomophagous arthropods have been introduced either intentionally (through the practice of biological control) or unintentionally to new regions. We examine interactions of these aliens with their new environments in the context of rapid global change linked to human activity. We consider effects of such interactions on establishment and spread of the alien species and effects on indigenous biota and ecosystems. Major elements of global change that affect alien-environment interactions include landscape modifications by humans (e.g., cultivation, habitat loss and fragmentation) and increases in atmospheric CO₂ and other gases resulting in climate change and other effects (e.g., changes in food quality for herbivores that affect higher trophic levels as well). Alien arthropod predators can alter landscapes for their benefit, to the detriment of indigenous species. A brief review also of blood-feeding alien arthropods makes clear that interactions with the environment critically influence invasions of zoophagous arthropods in general.