Showing papers in "Annual Review of Entomology in 2004"

The gut bacteria of insects: Nonpathogenic interactions

Abstract: The diversity of the Insecta is reflected in the large and varied microbial communities inhabiting the gut Studies, particularly with termites and cockroaches, have focused on the nutritional contributions of gut bacteria in insects living on suboptimal diets The indigenous gut bacteria, however, also play a role in withstanding the colonization of the gut by non-indigenous species including pathogens Gut bacterial consortia adapt by the transfer of plasmids and transconjugation between bacterial strains, and some insect species provide ideal conditions for bacterial conjugation, which suggests that the gut is a "hot spot" for gene transfer Genomic analysis provides new avenues for the study of the gut microbial community and will reveal the molecular foundations of the relationships between the insect and its microbiome In this review the intestinal bacteria is discussed in the context of developing our understanding of symbiotic relationships, of multitrophic interactions between insects and plant or animal host, and in developing new strategies for controlling insect pests

Plant-insect interactions in fragmented landscapes.

Abstract: Population and community ecology need a large-scale perspective because local patterns (of biodiversity) and processes (trophic interactions) are influenced by the regional setting. The ratio of the foraging range and/or dispersal ability to the distance between landscape elements influences local population dynamics. The spatial scale experienced by a species may be linked to its trophic level and also to traits such as body size, resource specialization, rarity, and population size variability. Hence, communities are assemblages of species with different spatial strategies. Effects of habitat loss and habitat fragmentation on plant-herbivore, herbivore-enemy, as well as plant-pollinator interactions are contingent on species and landscape. Metapopulation theory provides a unifying frame to approach plant-insect systems across fragmented landscape, although the landscape context is often ignored. In some cases theory is far ahead of empirical research. We call for more population data on large spatial and temporal scales to better understand plant-insect populations across fragmented landscapes.

The biology of xylem fluid-feeding insect vectors of Xylella fastidiosa and their relation to disease epidemiology.

Abstract: Xylophagous leafhopppers are common and abundant insects of tropical and subtropical environments and play important ecological roles in these ecosystems. The feeding biology of these insects is unique in terms of their high feeding rates and a digestive physiology that allows them to assimilate amino acids, organic acids, and sugars at approximately 99% efficiency. For those species well studied, fluctuations in plant xylem chemistry and tension appear to determine the diurnal and seasonal use of their host plants. Relatively few species of xylem fluid-feeding leafhoppers are considered important pests in commercial agriculture, as they transmit the bacterial plant pathogen Xylella fastidiosa. X. fastidiosa induces diseases of grapevines, citrus, coffee, almond, alfalfa, stone fruits, landscape ornamentals, and native hardwoods for which there is no cure. Two Xylella diseases, citrus variegated chlorosis (CVC) and Pierce's disease (PD) of grapevines, have emerged as important issues within the past decade. In Brazil, CVC became important in the early 1990s and has now expanded throughout many citrus-growing areas of South America and threatens to spread to North America. The recent establishment of the exotic glassy-winged sharpshooter (Homalodisca coagulata) in California now threatens much of the United States' wine grape, table grape, and almond production. The spread of H. coagulata throughout southern California and the spread of CVC northward from Argentina through Brazil exemplifies the biological risks from exotic species. The occurrence and epidemiology of leafhopper-vectored Xylella diseases are discussed.

WASP PARASITOID DISRUPTION OF HOST DEVELOPMENT: Implications for New Biologically Based Strategies for Insect Control*

Abstract: Wasp parasitoids use a variety of methods to commandeer their insect hosts in order to create an environment that will support and promote their own development, usually to the detriment of the host insect. Parasitized insects typically undergo developmental arrest and die sometime after the parasitoid has become independent of its host. Parasitoids can deactivate their host's immune system and effect changes in host hormone titers and behavior. Often, host tissues or organs become refractory to stimulation by tropic hormones. Here we present an overview of the manipulative capabilities of wasp-injected calyx fluid containing polydnaviruses and venom, as well as the parasitoid larva and the teratocytes that originate from the serosal membrane that surrounds the developing embryo of the parasitoid. Possibilities for using regulatory molecules produced by the parasitoid or its products that would be potentially useful in developing new, environmentally safe insect control agents are discussed.

DEFENSIVE BEHAVIOR OF HONEY BEES: Organization, Genetics, and Comparisons with Other Bees

Abstract: One key advantage of eusociality is shared defense of the nest, brood, and stored food; nest defense plays an important role in the biology of eusocial bees. Recent studies on honey bees, Apis mellifera, have focused on the placement of defensive activity in the overall scheme of division of labor, showing that guard bees play a unique and important role in colony defense. Alarm pheromones function in integrating defensive responses; honey bee alarm pheromone is an excellent example of a multicomponent pheromonal blend. The genetic regulation of defensive behavior is now better understood from the mapping of quantitative trait loci (QTLs) associated with variation in defensiveness. Colony defense in other eusocial bees is less well understood, but enough information is available to provide interesting comparisons between A. mellifera and other species of Apis, as well as with allodapine, halictine, bombine, and meliponine bees. These comparative studies illustrate the wide variety of evolutionary solutions to problems in colony defense in the Apoidea.

THE AFRICAN HONEY BEE: Factors Contributing to a Successful Biological Invasion*

Abstract: The African honey bee subspecies Apis mellifera scutellata has colonized much of the Americas in less than 50 years and has largely replaced European bees throughout its range in the New World. The African bee therefore provides an excellent opportunity to examine the factors that influence invasion success. We provide a synthesis of recent research on the African bee, concentrating on its ability to displace European honey bees. Specifically, we consider (a) the genetic composition of the expanding population and the symmetry of gene flow between African and European bees, (b) the mechanisms that favor the preservation of the African genome, and (c) the possible range and impact of the African bee in the United States.

Regulation of intermediary metabolism and water balance of insects by neuropeptides.

Abstract: Neuropeptides regulate all important physiological, developmental, and behavioral processes in insects. Here, I review two major physiological events that are hormonally controlled, namely intermediary metabolism and ion and water transport. Peptides belonging to the family of adipokinetic hormones (AKHs) increase hemolymph carbohydrates, lipids, and proline by activating the enzyme glycogen phosphorylase or lipase in the fat body. Moreover, these pleiotropic and multifunctional peptides inhibit protein-, lipid-, and RNA synthesis, and stimulate the frequency of contraction of certain muscles. Diuretic hormones that are related to the vertebrate corticotropin-releasing factor (CRF-related DHs) or belong to the family of kinins (which also have a myotropic action) or the cardioacceleratory peptides (CAPs), which increase the frequency of the heartbeat, all stimulate the secretion of fluid in Malpighian tubules (MTs) in vitro. Only a few true antidiuretic hormones are known: those from mealworms that inhibit the fluid transport in MTs in vitro, probably neuroparsins that stimulate water absorption by everted rectal sacs in vitro, and the desert locust's ion-transport peptide (ITP). Biosynthesis, release, receptors, mode of action, inactivation, structure-activity studies, and biological functions are discussed for the various peptides.

ERADICATION OF THE MELON FLY, BACTROCERA CUCURBITAE, IN JAPAN: Importance of Behavior, Ecology, Genetics, and Evolution

Abstract: The melon fly, Bactrocera cucurbitae, is a destructive insect of cucurbit and other fruits. It invaded the Southwestern Islands of Japan from 1919 to 1974. The sterile insect technique (SIT) was successfully applied from 1972 to 1993 to eradicate the melon fly. Technical research into SIT functions, such as suppression of density, mass-rearing, sterilization, shipment, release, evaluation of efficacy, and quality control of mass-reared insects, was conducted for this eradication project. Fundamental research into the dispersion, mating and oviposition behavior, population dynamics and estimation of density, eradication models, spatial distribution, genetics, and evolution of the melon fly was also undertaken and supported the success of the eradication project.

Polydnavirus genes and genomes: emerging gene families and new insights into polydnavirus replication.

Abstract: Polydnavirus genome sequencing is providing new insights into viral genome organization and viral gene function. Sequence analyses demonstrate that the genomes of these viral mutualists are largely noncoding but maintain genes and gene families that are unrelated to other viral genes. Interestingly, these organizational patterns in polydnavirus genomes are evident in both the bracovirus and ichnovirus genera, even though these two genera are evolutionarily unrelated. The identity and function of some polydnavirus gene families are considered with some functions experimentally supported and others implied by homology relationships with known insect genes. The evidence relative to polydnavirus origins and evolution is considered but remains an area of speculation. However, sequencing of these viral genomes has been informative and provides opportunities for productive investigation of these unusual mutualistic insect viruses.

Biological control of cereal aphids in north america and mediating effects of host plant and habitat manipulations.

Abstract: The predator and parasitoid fauna associated with cereal aphids is described, emphasizing the fauna associated with classical biological control efforts against the greenbug and Russian wheat aphid. We focus on literature from North America and include work from Europe and elsewhere when it is desirable to draw contrasts between approaches that affect cereal aphid biological control. Effects on natural enemies of cereal aphids are described that appear associated with plant traits that are innate, bred, or induced by aphid feeding. Examples of habitat manipulations, within and bordering cereal fields and within the broader landscape in which cereal production resides, affecting predators and parasitoids of cereal aphids are presented. These mediating effects of host plant and habitat manipulations on cereal aphid biological control provide significant and underexplored avenues to optimize cereal aphid management.

Human lice and their control

Abstract: ▪ Abstract Current research on human louse biology has focused on the long-standing debate about speciation of head and body lice but using new tools of DNA and enzyme analysis. These studies have indicated that head and body lice from the same geographical zone may be more closely allied than insects inhabiting the same ecological niche in other regions. However, the majority of research over the past decade has involved clinical aspects including transmission, treatment, and the appearance and identification of resistant strains within populations of lice. Despite advances, there is a need for a better understanding of louse biology, as existing therapies fail and lice remain potential vectors of disease for millons of people.

Phylogeny and Biology of Neotropical Orchid Bees (Euglossini)

Abstract: ▪ Abstract Orchid bees (Euglossini), noted for their brilliant iridescence, are elusive pollinators throughout the American tropics. Males are especially important in the pollination of some orchids, from which they collect aromatic fragrances thought to play a role in territorial display and courtship. The tribe contains approximately 190 described species divided among five genera, distributed from Mexico to central Argentina. Relatively intense study of their biology in the 1960s through the mid-1980s shed light on their nesting biology, chemical ecology, and classification. Vigorous taxonomic research led to the naming of many new species, revisions, and checklists, but phylogenetic studies were scarce. In the two decades following the last comprehensive review, phylogenetic research has resulted in new hypotheses of generic relationships, and further examination of male display has led to additional interpretations. Females in natural and artificial nesting cavities have revealed social interactions ...

GALLING APHIDS: Specialization, Biological Complexity, and Variation

Abstract: Gall-inducing aphids are host specific in the gall stage. Most species alternate between trees (the primary host), where the gall is induced, and shrubs and grasses (secondary hosts). Parthenogenesis during most of their life cycle is interrupted by a single stage of sexual reproduction on the primary host. Apart from these general characteristics, galling aphids present some of the most complex and diverse life histories in the insect world. In this article I review the specialized characteristics of galling aphids, as well as their complex and diverse life histories, as reported in the past 20 years.

Population genetics of autocidal control and strain replacement

Abstract: The concept that an insect species' genome could be altered in a manner that would result in the control of that species (i.e., autocidal control) or in the replacement of a pestiferous strain of the species with a more benign genotype was first proposed in the mid-twentieth century. A major research effort in population genetics and ecology followed and led to the development of a set of classical genetic control approaches that included use of sterile males, conditional lethal genes, translocations, compound chromosomes, and microbe-mediated infertility. Although there have been a number of major successes in application of classical genetic control, research in this area has declined in the past 20 years for technical and societal reasons. Recent advances in molecular biology and transgenesis research have renewed interest in genetically based control methods because these advances may remove some major technical problems that have constrained effective genetic manipulation of pest species. Population genetic analyses suggest that transgenic manipulations may enable development of strains that would be 10 to over 100 times more efficient than strains developed by classical methods. Some of the proposed molecular approaches to genetic control involve modifications of classical approaches such as conditional lethality, whereas others are novel. Experience from the classical era of genetic control research indicates that the population structure and population dynamics of the target population will determine which, if any, genetic control approaches would be appropriate for addressing a specific problem. As such, there continues to be a need for ongoing communication between scientists who are developing strains and those who study the native pest populations.

LONG-TERM, LARGE-SCALE BIOMONITORING OF THE UNKNOWN: Assessing the Effects of Insecticides to Control River Blindness (Onchocerciasis) in West Africa

Abstract: ▪ Abstract The control of river blindness (onchocerciasis), a human disease transmitted by black flies, has been an economic and public health success in West Africa. It involved insecticide applications to as many as 50,000 km of rivers, almost weekly, in 11 countries between 1974 and 2002. The long-term biomonitoring of the effects of insecticide use on the nontarget invertebrate (primarily insect) and fish communities was initially designed on the basis of limited knowledge available for West African rivers and on information from other areas. Routine monitoring surveys demonstrated little effect on fish but produced inconclusive results for invertebrates. Research conducted beyond these surveys and current views in river and general ecology indicate that permanent damage to invertebrates from insecticiding was unlikely. The scientific progress made during the 29 years of this biomonitoring program is relevant to future, large-scale, long-term programs worldwide.

Benjamin Dann Walsh: pioneer entomologist and proponent of Darwinian theory.

Abstract: ▪ Abstract Many entomologists are generally unacquainted with the life and scientific contributions of Benjamin Dann Walsh, the first State Entomologist of Illinois and an early proponent of Darwinian theory. This historical oversight is unfortunate because Walsh was both a pioneer in entomology and the only entomologist of his and Darwin's generation to support and contribute to Darwin's revolutionary theory of species origin. In this review, I attempt to return Walsh to his rightful place among the more fascinating and progressive scientists of the nineteenth century. The review comprises three sections: the first provides a biographical sketch of Walsh's rich and varied life in England and the United States; the second considers his entomological endeavors and legacy; and the third argues for Walsh's prescient advocacy of, and contributions to, evolutionary theory. Also included are passages from some of Walsh's publications and excerpts from his correspondence with Darwin and notable entomologists.