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BASIC INSECT BIOLOGY

Programs within the Department of Entomology are built on a foundation of basic biology, but the amount of basic research currently being conducted varies widely from program to program. This results in a healthy mix of research perspectives that promotes the department’s overall mission to study insect related problems in Louisiana. Here I describe the role of basic biological research in the department. This summary is based on input I have received from 11 faculty members that consider basic research to be a component of their overall research activities. Since basic research is conducted in each of the major research domains within the department, I have organized my comments according to those domains, including Extension, Integrated Pest Management, Urban Entomology, and Basic Biology.

The main function of the Extension Service is to provide information transfer services to the public and serve on the front lines for pest and invasive species surveys. These are practical pursuits that may be regarded as removed from strictly defined basic biological research, but they require a firm knowledge base of basic entomology and often require research into more basic questions of insect biology and life history.

One primary role of extension in the study of insects is to ensure that identifications are made correctly and that the public desire for knowledge about insects is satisfied. These are cooperative endeavors among extension scientists at the public interface and research biologists engaged in systematic and life history research. Extension specialists maintain collections that are necessary for confirmation of identifications and collect basic life history information to provide biological context for specimens submitted by the public for identification. The Louisiana State Arthropod Museum (LSAM) cooperates with the Extension Service by assisting with insect identification and providing information about the basic biology of species in question. The delivery of such basic information ensures that entomological problems are correctly diagnosed and dealt with and serves both the public and the field of entomology by feeding the entomological curiosity of the citizens of Louisiana and promoting entomology as the fascinating field of science that it is.

The Extension Service performs outreach services that focus on basic study of insects from an instructional perspective. Information on identification of insects, biodiversity, and insect biology are delivered to agents and the public through educational programs, bulletins, mass media, and distance learning programs.

Research on basic insect biology is the foundation of sound insect pest management because the strategies that are utilized in suppressing insect populations exploit vulnerable life history attributes of the target insects, most commonly related to behavior or physiology, or manipulation of natural enemies. Closely related insect species may respond very differently to specific kinds of management strategies so correct taxonomic determinations are central to ensuring that the target pests are indeed what the investigators think they are. Taxonomic needs of the department are supported by a comprehensive collection of insects and taxonomic literature housed in the LSAM. These resources allow fast, accurate determinations of insects for assessing threats or potential benefits (as natural control organisms) to Louisiana’s agricultural and urban settings. For example, the sugarcane monitoring program for Mexican rice borer (Euroma lofteni) relies on comparison of material in the LSAM and morphological study of genitalia for separating this species and similar appearing pyralid moths.

Many projects related to traditional agriculture and forestry in Louisiana involve basic entomological research at some level. Investigations of pheromone components of Phyllophaga species seek to determine population peaks and seasonal movements into crops. These researchers and their collaborators at the University of Georgia are also studying behavioral responses of sweet potato weevil (Cylas formicarius) to volatile components of potato skins to determine if antibiosis factors vary from one variety to another. Finally, host range and environmental tolerances of sweet potato weevil are being investigated to determine patterns of seasonal survival and reproduction in Louisiana.

The most significant threat to rice in Louisiana is the rice water weevil (Lissorhoptrus oryzaephilus). To complement applied research projects in rice, basic research is being conducted in a variety of areas. The goal of these projects is a better understanding of how extrinsic (environmental) and intrinsic factors (e.g., plant genotype and ontogeny) interact to determine the expression of resistance to herbivory by plants. Studies that are underway include age related changes in susceptibility of rice plants to herbivore damage, the effects of flooding and other cultural practices on weevil behavior, use of weedy and native host plants, plant-mediated interactions between rice water weevil and fall armyworm (Spodoptera frugiperda), and pheromone identification studies. Intradepartmental collaborative research seeks to determine whether an entomopathogenic fungus can spread among populations of several insect host species on two or more insect host plants. The immediate goal of laboratory and field studies is to demonstrate the feasibility of this approach using rice water weevil as the primary insect host.

In soybeans, another collaborative project focuses on the use of exogenous jasmonic acid to stimulate resistance of soybean plants to herbivores and pathogenic microorganisms. Jasmonic acid is a plant hormone involved in the biochemical response of many plants to herbivory that may be a useful tool in plant resistance research.

Four areas of forest insect research have basic components. The first investigates the role of bark beetle (Curculionidae: Scolytinae) vision and their behavioral responses to silhouettes and semiochemical cues as part of their host selection processes. The second involves identification, basic predator development, behavior, and competition among histerid predators of bark beetles. Third, in sensitive forested wetlands evaluates the impacts of nutrients and salinity in a flooded environment on early season defoliators and their interactions on tupelo and baldcypress productivity. The fourth area investigates the interactions of fire and insects on tree health, particularly with respect to resin responses in longleaf pine trees. All of these basic projects relate to practical problems of forest management and have potential to lead to applied programs in forest pest management and modeling of tree health and forest productivity.

Several IPM-related projects involve research on important pest species that are relevant to a range of crop systems. Toxicology research on the tobacco budworm (Heliothis virescens) is investigating resistance mechanisms and regulation of the expression of detoxification enzymes (e.g., mixed-function oxidases, glutathione S-transferases, and esterases). Such enzymes are used by insects to detoxify insecticides and plant toxins, but the mechanism by which insects "sense" which forms of these enzymes are needed in response to toxic insult is not known. These avenues of inquiry also have relatively obvious relevance to enhancing pest management of this and related pest insects, including development assays allowing unambiguous identification of resistance mechanisms.

An intradepartmental collaborative project is investigating the effect of two grass chemicals on fall armyworm. Ferulic acid and p-coumaric acid are structurally related plant compounds common in grasses that have widely divergent effects on fall armyworm growth and development. The immediate goal of this collaboration is to provide a biochemical and toxicological explanation for the differential toxicity of these two compounds.

A multidepartmental (with the Dept. of Agronomy), multinational (with World Laboratory Ukrainian Branch) project is investigating Ukrainian isolates of Bacillus thuringiensis to discover Bt Cry gene products with high levels of activity against Louisiana insects. Currently, experiments are underway to assay Ukrainian Bt Cry toxins against tobacco budworm, sugarcane borer (Diatraea saccharalis), fall armyworm, cabbage looper (Pseudoplusia includens), soybean looper (Trichoplusia ni), boll weevil (Anthomomus grandis), sweet potato weevil, red imported fire ant (Solenopsis invicta), and Formosan termite (Coptotermes formosanus). A separate project in insect pathology seeks to determine whether single-gene alterations in genomes of viruses alter their ecology. This also is a multi-institutional endeavor (with University of California, Davis and DuPont Chemical).

Basic biological research in urban entomology in the entomology department mirrors our major programs of applied research on the Formosan subterranean termite and red imported fire ant.

Basic research on the Formosan termite explores colony dynamics. Specifically, mechanisms are being investigated that control colony development and behavior through pheromones, foraging decisions and division of labor, and intraspecific/interspecific interactions. Recent research on the components of the frontal gland of soldier termites has identified several proteins that are new to science. On another front, investigations on how some plants can avoid termite attack have identified the plant compound nootkatone, found in vetiver grass, as an important repellent, potentially with wide-ranging applications. Intradepartmental collaborators are searching for new strains of entomopathogenic fungi with the capability to produce disease epizootics in termite populations. Isolation and screening of fungi against Formosan termite are underway, along with evaluations of transmission, replication, and virulence of these pathogens.

The main thrust of basic research on the red imported fire ant involves a multidepartment and multi-institutional (with LSU Dept. of Biological Sciences, USDA, Gainesville, and Texas A & M University) investigation of the role of pathogen transmission in the establishment of microsporidia. These pathogens include Thelohania solenopsae, a recently released non-indigenous species, and a naturally-occurring microsporidium. Electron microscopy is clarifying transmission of the former and the identity of the latter. Other research explores nutritional flow and ant-vertebrate interactions in the red imported fire ant.

The systematics, biodiversity, and conservation biology programs within this and most other departments of entomology at Land Grant institutions are generally perceived as being at the basic end of the basic-applied continuum. Systematics, in particular, is concerned with fundamental questions dealing with taxonomic diversity, patterns of evolution, and natural history. The fact that systematic entomology forms a substantial amount of the foundation of all other entomological research, whether basic or applied requires that it be included in the overall research program of any healthy department of entomology.

Insect-centered conservation biology research is a relatively recent natural outgrowth of the overall increase in conservation biology research during the past 25 years or so. Insects represent a vast underutilized resource for sorting out the impacts of human induced changes to ecosystems and for monitoring recovery and restoration of degraded habitats. Conservation biology is mainly an applied field where relatively well-studied groups such as vascular plants and mammals are concerned. Application of insect data to ecological decision making is hampered by a lack of baseline information on insect diversity patterns across natural ecosystems and systematic barriers such as a lack of qualified specialist to sort and identify species. Thus, insect conservation biology research in the LSU Department of Entomology is mainly concerned with establishing good comparative data bases of insect diversity patterns in naturally occurring habitats that are of special significance to the state of Louisiana. Habitats that are the primary focus of current research projects are longleaf pine savannas and mixed mesophytic hardwood forest remnants.

Current projects in longleaf pine remnants involve documenting overall diversity of selected insect taxa (various moth and beetle families, and ants) across a variety of longleaf pine habitat types (e.g., upland sandy, flatwood clay hardpan) (in collaboration with The Nature Conservancy). In addition to developing general baseline information about insect diversity in Louisiana longleaf pine, specific goals are to document habitat specialists and species assemblages that vary predictably in response to human induced treatments. Treatments that are currently being investigated include seasonal timing and frequency of controlled burns and suppression of red imported fire ants. A long term restoration project at Abita Creek Preserve, a Nature Conservancy project in St. Tammany Parish, will allow long term (10+ years) monitoring of insect populations in response to restoration of a heavily modified and degraded longleaf pine flatwood.

Projects in Tunica Hills region in West Feliciana Parish similarly focus on long term studies on insect diversity on several different mixed mesophytic forest stands representing a range of habitat quality from mature beech-magnolia forest to intermediate succession disturbed forest having a substantial numbers of loblolly pines. Studies are being conducted to document comparative diversity of forest litter spiders and taxonomic research is underway on several families of beetles, including Staphylinidae, Endomychidae, Nitidulidae, and Histeridae. The goal of these taxonomic studies is the discovery of undescribed or previously unrecorded disjunct species in Louisiana and characterization of their habitat associations.

A major initiative with a southeastern U.S. regional focus is the development of a sorting center for the Coleoptera component of the All Taxon Biodiversity Inventory (ATBI) of Great Smoky Mountains National Park (GSMNP). This is an ambitious effort to survey all organisms living within the park and involves a consortium of government and non-government organizations, academic institutions, and amateur taxonomists.

In addition to local or regionally-focused projects, we are engaged in a number of revisionary and monographic projects on the beetle families Staphylinidae, Histeridae, and Nitidulidae in a global context, with ongoing projects in the neotropics and New Zealand with collaborators at State University of New York, Syracuse and Landcare Research, Auckland, New Zealand.

From a basic research perspective, what do we wish to gain from this review? We seek an objective evaluation of short and long term plans for sustaining and improving basic insect biology research programs in the LSU Department of Entomology, including a critique of current programs, and suggestions for the future that address the following specific areas of concern.

Balance: In programs having split problem-directed and basic research responsibilities, what guidelines should be followed in achieving an appropriate balance between basic and applied projects? What basic avenues of research are most appropriate, given the overall mission or our department? Encouraging scientists to design programs that are most appropriate to their areas of expertise and conducive to research productivity is paramount to achieving this balance.

Downsizing: Do we risk loosing an effective critical mass for basic research through downsizing, and what effect might this process have on attracting top quality graduate student researchers and new faculty? How can we mitigate decline in the amount and quality of basic research if cuts are inevitable? Increased use of scientists on sabbatical leave and participation through adjunct appointments have been mentioned as parts of a solution to this problem.

Promotion and technology transfer: How can we do a better job of selling the value of basic research and promote its rapid and efficient application to problem-oriented research? This is a particularly relevant concern in the increasing atmosphere of accountability. Increased media contact and promotion of basic research, instructional entomology workshops for educators, increased levels of communication and collaboration between research and extension scientists all have potential to address this concerns.

Program Goals: Develop a better understanding of the diversity and relationships of insects and related arthropods through collection-based systematic research.

Major Activities: Most work conducted in the Louisiana State Arthropod Museum involves the systematics of various groups of beetles and general survey work of forest litter arthropod communities. Systematic revisions and monographs are being prepared for taxa within the following families of beetles: Staphylinidae, Histeridae, Nitidulidae, Endomychidae. Staphylinid and nitidulid beetle projects are global in scale. International-scale systematics projects are being conducted in New Zealand (Staphylinidae and associated Laboulbeniales fungi) and tropical America (Staphylinidae, Nitidulidae, and Histeridae).

Forest litter arthropod work involves site and habitat comparisons using spiders and beetles in mixed mesophytic forest habitats on the Gulf Coastal Plain.

The field of forensic entomology is being expanded into prosecution of wildlife poaching through an analysis of entomological faunal succession on carcasses of various kinds of high profile game animals and wildlife. This project is also producing many new records and range extensions of necrophilous insects for Louisiana.

Analysis of the status of insect conservation research in the United States is being conducted to determine taxonomic bias in conservation lists. This project bridges the gap between traditional taxonomy and systematics and the emerging applied field of entomologically-centered conservation biology.

Personnel: Victoria Moseley, Curator of the LSAM. Duties: Day to day management of the LSAM collections, researcher in nitidulid beetle taxonomy. Alexey Tishechkin, Graduate Research Assistant. Duties: Research on systematics of histerid beetles. Andrew Cline, Graduate Research Assistant. Duties: Research on systematics of nitidulid beetles. Graduate Research Assistant Erin Watson. Duties: Research program in forensic entomology. Graduate Student Joyce Fassbender. Duties: Research in forest litter spider diversity.

Cooperators: Janice Bossart (College of New Jersey, Ewing, NJ), Alex Weir (State University of New York, Syracuse, NY), Richard Leschen (Landcare Research, Auckland, New Zealand), Donald Chandler (University of New Hampshire, Durham, NH).

Experiment Station Project LAB 03344: Entomological Systematics and Improvement of the Louisiana State Arthropod Museum

Objectives: Develop an internationally recognized research program in insect systematics. Apply arthropod systematics research to address conservation problems in Louisiana. Support the taxonomic needs of the Department of Entomology and the citizens of Louisiana.

Program goals: 1) Test hypotheses regarding evolution of parasite virulence by determining whether single-gene alterations in genomes of nucleopolyhedroviruses (NPV) alters their ecology. 2) Clarify the identities, life cycles, and transmission of certain microsporidian pathogens of red imported fire ant (RIFA). 3) Discover Bacillus thuringiensis (BT) Cry gene products with activity against Louisiana pests.

Major Activities: 1) A series of experiments over several years is indicating that NPVs may evolve for increased virulence but only to a point where their fitness begins to decrease. This research has included reproduction, persistence, and biotic transport of recombinant and wild-type NPVs. Current research is concentrating on abiotic transport. 2) Light and electron microscopy has identified three types of spores in the life cycle of the microsporidium Thelohania solenopsae, which does not occur in Louisiana; these spore types may be specialized for auto-infection and horizontal and vertical transmission. A different microsporidian species occasionally is found in Louisiana and will be identified. 3) BT Cry toxins are being bioassayed against tobacco budworm, sugarcane borer, fall armyworm, cabbage looper, soybean looper, boll weevil, sweet potato weevil, RIFA, and Formosan termite. One isolate was more virulent than standard BTs to cabbage looper. Purified, high-molecular-weight toxins from two isolates were more virulent than standards to sugarcane borer.

Personnel: Arthur Richter, Research Associate, runs the virus experiments. Dr. Ioulia Y. Sokolova, Post Doctoral Researcher, is responsible for the fire ant/microsporidium research. Dr. Irina A. Isakova, Post-Doctoral Researcher, is responsible for the BT research.

Cooperators: Microsporidia in fire ants: Dr. Earl Weidner (Dept. Biological Sciences, LSU). Discussions are underway to cooperate with Dr. Bradley Vinson (Texas A&M Univ.)/BT toxins: Dr. V. Kordium (World Laboratory Ukrainian Branch, Kiev); Dr. James Oard (Dept. Agronomy, LSU AgCenter)

USDA Grant #98-33120-6435 (LAES Project LAB 03357): Soil-to-Plant Transport of Recombinant Insect Virus. Objectives: 1) Quantify the effects of abiotic variables on soil-to-plant transport of a recombinant nucleopolyhedrovirus (NPV) in a greenhouse microcosm. 2) Quantify soil-to-plant transport of the recombinant NPV in a cotton agroecosystem.

Regional Project S-301 (LAES Project LAB03485): Development, Evaluation and Safety of Entomopathogens for Control of Arthropod Pests. Objectives: 1) Development, evaluation and safety of entomopathogens for control of leaf feeding insect defoliators, 3) Development, evaluation and safety of entomopathogens used in cryptic and soil habitats.

Program Goals: Provide a fundamental basis for the management of insecticide-resistant populations of pest insects.

Program Objectives: The short-term objective of these studies is to identify, characterize, and measure expression of physiological and biochemical mechanisms underlying insecticide resistance. Information from these studies is being used to enhance our understanding of: 1) how insecticide resistance evolves in natural populations, 2) fitness deficits associated with the expression of resistance, and 3) potential countermeasures for use against resistant pests. Our long-term goal is to develop diagnostic kits with field utility to detect expression of resistance mechanisms, and to provide substantive input into resistance management algorithms.

Major Activities: The primary focus of research has been mechanisms of resistance to pyrethroid and organophosphate insecticides in the tobacco budworm, Heliothis virescens. Until recently, this insect was the key pest of cotton grown in the midsouth, and in most years, infested and damaged 100% of the Louisiana crop. Our initial efforts were to develop robust methods for detecting expression of the three major resistance mechanisms (reduced penetration, enhanced metabolism, and altered target sites) in field-collected populations of this insect. Pharmacokinetic, biochemical and physiological assays were developed, optimized, and used to document expression of all three mechanisms in both organophosphate- and pyrethroid-resistant insects. In pyrethroid-resistant budworms, frequencies of expression of the two major resistance mechanisms varied during the growing season: frequencies of metabolic resistance increased (but the target-site mechanism decreased) from early to late season collections. These studies were the first to document "mechanism switching" in natural populations of resistant insects. In studies with organophosphate-resistant insects, expression of resistant mechanisms was dependent upon selection pressure at the location sampled. In regions where insecticides were applied frequently, target-site mechanisms predominated and reached frequencies of 60% or greater. In less-selected regions, metabolic mechanisms predominated. The dynamics of resistance mechanisms in wild populations are being studied further.

Hatch Project: LAB03306 Biochemical and Physiological Mechanisms of Insecticide Resistance

Collaborators: Roger Leonard, Steve Micinski

Program Goals and Activities: My research is centered primarily on factors influencing and causing diversity in insects. My conservation biology research involves generating an inventory of the fauna, uses biogeography and life history data to determine indigenous species, and then focuses on the role or function of indigenous or exotic species in the ecosystem. This work has typically had direct ramifications for management of the habitat to preserve unusual components of the fauna. The past five years have generated inventories for several ecosystems in Louisiana. We are narrowing in on indigenous species and are just beginning to conduct research on functional roles. I have a molecular lab that is equipped for use in molecular systematics. Although this is not a primary research focus, since systematics plays such a vital role in determining faunal biogeographic affinities and also aids in understanding relationships of species in communities, I intend to maintain a foothold in this area. Lastly, for the past 25 years I have been actively involved in research on speciation patterns and processes. I expect this to continue to be an underlying thread of my research in threatened and endangered habitats in the southeast.

Personnel: Dee Colby, Ph.D. Graduate Student, anticipated graduation in August 2001, Dissertation: Effects of red imported fire ants and fire frequency on native insects in longleaf pine savannas.

Debra Murray, Ph.D. Graduate Student, anticipated graduation in August 2001, Dissertation: Systematics and the evolution of life history traits in euptychine butterflies.

Undergraduate Student workers: Michael Kober, Jayme Trahan, and Varsha Gillala.

Cooperators: Chris Carlton, (LSU); Deborah Landau (World Bank), Nelwyn McInnis (LA Nature Conservancy).