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At least 235 records · Page 13Linked to original sources
PubMed2006

Management of stinging insect hypersensitivity: a 5-year retrospective medical record review.

BACKGROUND: The Joint Task Force on Practice Parameters for Allergy and Immunology recommends that patients with a history of a systemic reaction to an insect sting be educated on ways to avoid insect stings, carry injectable epinephrine for emergency self-treatment, undergo specific IgE testing for stinging insect sensitivity, and be considered for immunotherapy. OBJECTIVE: To review frontline providers' documented care and recommendations for imported fire ant and flying insect hypersensitivity reactions. METHODS: A retrospective medical record review was performed of emergency department and primary care clinic visits between November 1, 1999, and November 30, 2004. Using International Classification of Diseases, Ninth Revision, codes, medical records were selected for review to identify patients with potential insect hypersensitivity. RESULTS: A total of 769 medical records from patients who experienced an insect sting were reviewed. Of 120 patients with a systemic reaction, 66 (55.0%) received a prescription for injectable epinephrine, and 14 (11.7%) were given information regarding avoidance of the offending insect. Forty-seven patients with systemic reactions (39.2%) were referred to an allergist. Of 28 patients who kept their appointments and underwent skin testing, 3 had negative results and 25 (89%) had positive results and were advised to start immunotherapy. CONCLUSION: Adherence to the stinging insect hypersensitivity practice parameter recommendations is poor. Many patients who have experienced a systemic reaction after an insect sting and have sought medical care are not afforded an opportunity for potentially lifesaving therapy.

Adolescent↗
PubMedDate not supplied

[Impact of microsporidia on hormonal balance in insect hosts].

Microsporidia (M) is a phylum of protists parasitizing obligatory in animal cells. Long way of adaptation of M to intracellular parasitism resulted in establishment of quite close relationships between the parasite and its host. Different species of M induce in their hosts symptoms similar to those caused by misbalance of juvenile hormone (JH) and ecdysone. M infection leads to pathology of different hormone-dependent functions such as cell differentiation and specialization, molting, metamorphosis, diapause and reproduction of insects. The signs of hormonal dysfunction evidence for elevated titer of JH in M-infected insects. Two possible explanation of this could be offered: JH secretion by M or specific influence of the parasites on the insect endocrine systems. Impact on insect endogenous JH titer by M could be mediated by affection of secretory activity of corpora allata or by suppression of enzymatic degradation of JH. According to different hypotheses, insect hormonal status during microsporidiosis could be modified by a) insect host stress-reaction, b) exhaustion of insect host reserves, characteristic for acute phase of the disease, c) destruction of infected insect cells and tissues during mass sporogenesis of M. Data found in literature and provided by our experiments evidence for presence of JH analogues or juvenilizing substance in the extracts of M spores. From detailed examination of pathological process it is also seen that juvenilizing effect of M infection is usually restricted to the invaded regions of tissues (i.e. expressed locally) but not a systemic one. Ability of M to modify morpho-functional features of infected tissues at the level of hormonal regulation is undoubtfully a prominent adaptation for stabilizing "microsporidia-insect" parasite-host systems.

Adaptation, Physiological↗
PubMed2000

Pyruvate cycling and implications for regulation of gluconeogenesis in the insect, Manduca sexta L.

Pyruvate cycling was examined in the insect Manduca sexta L. (2-(13)C)pyruvate was injected into 5th instar larvae maintained on a semisynthetic high sucrose, low sucrose, or sucrose-free diet. Pyruvate cycling and gluconeogenesis were determined from the distribution of (13)C in blood metabolites, including trehalose, the blood sugar of insects, and alanine. Pyruvate cycling was evident from the (13)C enrichment of alanine C3, synthesized by transamination of pyruvate following carboxylation to oxaloacetate and cycling through phosphoenolpyruvate. Based on the relative (13)C enrichments of alanine C2 and C3, insects maintained on the high sucrose diet displayed higher levels of cycling than insects on the other diets. Insects on all the diets, when subsequently starved, displayed low levels of cycling. Gluconeogenesis was evident in insects on sucrose-free or low sucrose diets from the selective (13)C enrichment in trehalose. The level of gluconeogenesis relative to glycolysis was indicated by the (13)C enrichment of trehalose C6 and alanine C3, both enrichments metabolically derived in the same manner. Insects starved after maintenance on the sucrose-free or low sucrose diets remained glucogenic. Insects on the high sucrose diet were not glucogenic, and subsequent starvation did not induce gluconeogenesis. The results indicate that pyruvate kinase plays a critical role in regulating the gluconeogenic/glycolytic balance, and that inhibition of pyruvate kinase is a principal regulatory event during induction of de novo trehalose synthesis. Gluconeogenesis failed to maintain homeostatic levels of blood trehalose, supporting the conclusion that blood sugar level may be important for mediating nutrient intake. Possible factors involved in the regulation of gluconeogenesis in insects are discussed.

Animals↗
PubMed1990

Mechanisms for regulating oxygen toxicity in phytophagous insects.

The antioxidant enzymatic defense of insects for the regulation of oxygen toxicity was investigated. Insect species examined were lepidopterous larvae of the cabbage looper (Trichoplusia ni), southern armyworm (Spodoptera eridania), and black swallowtail (Papilio polyxenes). These phytophagous species are subject to both endogenous and exogenous sources of oxidative stress from toxic oxygen radicals, hydrogen peroxide (H2O2) and lipid peroxides (LOOH). In general, the constitutive levels of the enzymes superoxide dismutase (SOD), catalase (CAT), glutathione transferase (GT), and its peroxidase activity (GTpx), and glutathione reductase (GR), correlate well with natural feeding habits of these insects and their relative susceptibility to prooxidant plant allelochemicals, quercetin (a flavonoid), and xanthotoxin (a photoactive furanocoumarin). Induction of SOD activity which rapidly destroys superoxide radicals, appears to be the main response to dietary prooxidant exposure. A unique observation includes high constitutive activity of CAT and a broader subcellular distribution in all three insects than observed in most mammalian species. These attributes of CAT appear to be important in the prevention of excessive accumulation of cytotoxic H2O2. Unlike mammalian species, insects possess very low levels of a GPOX-like activity toward H2O2. Irrefutable proof that this activity is due to a selenium-dependent GPOX found in mammals, is lacking at this time. However, the activity of selenium-independent GTpx is unusually high in insects, suggesting that GTpx and not GPOX plays a prominent role in scavenging deleterious LOOHs. The GSSG generated from the GPOX and GTpx reactions may be reduced to GSH by GR activity. A key role of SOD in protecting insects from prooxidant toxicity was evident when its inhibition resulted in enhanced toxicity towards prooxidants. The role of antioxidant compounds in protecting these insects from toxic forms of oxygen has not been explored in depth. A major finding, however, is that these insects are lutein accumulators. Lutein is a dihydroxy (diol) derivative of beta-carotene, and it is a good quencher of activated forms of oxygen and free radicals. Levels of lutein are highest in P. polyxenes which specializes in feeding on prooxidant-containing plants.

Animals↗
PubMed2005

Melanogenesis and associated cytotoxic reactions: applications to insect innate immunity.

Insects transmit the causative agents for such debilitating diseases as malaria, lymphatic filariases, sleeping sickness, Chagas' disease, leishmaniasis, river blindness, Dengue, and yellow fever. The persistence of these diseases provides testimony to the genetic capacity of parasites to evolve strategies that ensure their successful development in two genetically diverse host species: insects and mammals. Current efforts to address the problems posed by insect-borne diseases benefit from a growing understanding of insect and mammalian immunity. Of considerable interest are recent genomic investigations that show several similarities in the innate immune effector responses and associated regulatory mechanisms manifested by insects and mammals. One notable exception, however, is the nearly universal presence of a brown-black pigment accompanying cellular innate immunity in insects. This response, which is unique to arthropods and certain other invertebrates, has focused attention on the elements involved in pigment synthesis as causing or contributing to the death of the parasite, and has even prompted speculation that the enzyme cascade mediating melanogenesis constitutes an ill-defined recognition mechanism. Experimental evidence defining the role of melanin and its precursors in insect innate immunity is severely lacking. A great deal of what is known about melanogenesis comes from studies of the process occurring in mammalian systems, where the pigment is synthesized by such diverse cells as those comprising portions of the skin, hair, inner ear, brain, and retinal epithelium. Fortunately, many of the components in the metabolic pathways leading to the formation of melanin have been found to be common to both insects and mammals. This review examines some of the factors that influence enzyme-mediated melanogenic responses, and how these responses likely contribute to blood cell-mediated, target-specific cytotoxicity in immune challenged insects.

Animals↗
PubMed2004

Modeling the invasion of recessive Bt-resistant insects: an impact on transgenic plants.

There is a growing public concern on ecological and evolutionary consequence of the use of genetically modified organisms. We study the impact of Bt-resistant pests on genetically modified Bt crops. We develop and analyse a conceptual reaction-diffusion model of the Bt crop-Bt-susceptible insects-Bt-resistant insects to simulate the invasion of Bt-resistant insects. We show by means of computer simulations that there is a key parameter, which we define as the growth number that characterizes the insects' fitness. We also show that the Bt-resistant insect invasion can lead to inhomogeneity in plant and insect spatial distributions. The plant biomass is found to be essentially dependent on the duration of the Bt-resistant insect reproduction period. There are two types of this dependence. One of them exhibits, respectively, higher plant biomass in comparison with another. The ambiguity in the response of the Bt crop-Bt-susceptible insects system to the invasion of Bt-resistant insects can lead to serious complications in attempts to regulate the dynamics of the system.

Animals↗
PubMed2001

Laboratory evaluation of an improved electronic grain probe insect counter.

An Electronic Grain Probe Insect Counter system, which incorporates modified passive grain probes, allows offsite monitoring and detection of insect pests in stored grain. An electronic count is generated whenever an insect falls through an infrared beam in the sensor head located at the bottom of the electronic grain probe. We report descriptions and laboratory evaluations of prototype electronic grain probes that were custom-made in-house (n=8) and by small-scale manufacturing (n=54). Laboratory tests, in which dead insects were dropped through a probe, were conducted to determine if electronic probes accurately count the numbers of insects that are captured. Accuracy of the manufactured electronic probes increased as the size of the test insect increased from 93.6% for the smallest insect tested (Cryptolestes ferrugineus, the rusty grain beetle) to 99.5% for the largest (Tribolium castaneum, the red flour beetle). Custom-made probes were significantly more accurate for C. ferrugineus (96.5% versus 93.6%) but there was no difference in accuracies for the larger insects. Comparisons among all probes found that probe accuracy was correlated with variation in the magnitude of the output signal from the infrared phototransistor. Thus, use of diode/phototransistor pairs with a more consistent beam or with improved beam focus may further improve probe accuracy. Good performance was obtained with the manufactured electronic probes. Tests with live insects under field conditions are needed to further evaluate the system performance.

Journal Article↗
PubMed2001

Immigration of insects into bins storing newly harvested wheat on 12 Kansas farms.

Adult insects entering 34 bins (36-238 t capacity) storing newly harvested hard red winter wheat on 12 farms in Kansas were sampled from July through December 1998 using ventilation traps. Insects moving through the grain stored in these bins were sampled using probe traps. During the fourth week of storage, probe traps captured Cryptolestes ferrugineus in all bins, Ahasverus advena in 32 bins, Typhaea stercorea in 31 bins, and Rhyzopertha dominica in 13 bins. Means+/-SE of 5.6+/-0.7 C. ferrugineus, 0.5+/-0.2 R. dominica, 3.5+/-0.3 A. advena, and 3.5+/-0.7T. stercorea were caught per day in probe traps. Ventilation traps provided a more direct measure than probe traps of the total numbers of insects entering bins storing newly harvested wheat. Immigration of A. advena and T. stercorea increased more than that of other species during the storage period, exceeding that of C. ferrugineus and R. dominica during some weeks. Rhyzopertha dominica had the lowest immigration rate. Bin size did not influence ventilation trap catch but as many as a third more insects may immigrate into large bins at the eaves compared with small bins because of their larger circumference. The mean numbers of C. ferrugineus, R. dominica, A. advena and T. stercorea captured in ventilation traps at the bin cap were 7.8, 2.7, 15.1 and 18.3 times, respectively, those captured in ventilation traps at the bin eaves. The estimated means+/-SE for total numbers of insects entering a bin each day were 13.6+/-4.2 C. ferrugineus, 6.3+/-4.7 R. dominica, 5.8+/-1.4 A. advena, and 21.9+/-8.2T. stercorea. Estimates of immigration rates can improve the accuracy with which insect densities are predicted using insect population growth models, and allow computer models to be used more effectively in managing insect pests. Insect infestations may be reduced by screening the openings between the bin cap and the roof, or the roof and the side walls.

Journal Article↗
PubMed1999

Blood sugar formation due to abnormally elevated gluconeogenesis: aberrant regulation in a parasitized insect, Manduca sexta Linnaeus.

Alterations of carbohydrate metabolism associated with parasitism were examined in an insect, Manduca sexta L. In insect larvae maintained on a low carbohydrate diet gluconeogenesis from [3-13C]alanine was established from the fractional 13C enrichment in trehalose, a disaccharide of glucose and the blood sugar of insects and other invertebrates. After transamination of the isotopically substituted substrate to [3-13C]pyruvate, the latter was carboxylated to oxaloacetate ultimately leading to de novo glucose synthesis and trehalose formation. Trehalose was selectively enriched with 13C at C1 and C6 followed by C2 and C5. 13C enrichment of blood sugar in insects parasitized by Cotesia congregata (Say) was significantly greater than was observed in normal animals. The relative contributions of pyruvate carboxylation and decarboxylation to trehalose labeling were determined from the 13C distribution in glutamine, synthesized as a byproduct of the tricarboxylic acid cycle. The relative contribution of carboxylation was significantly greater in parasitized larvae than in normal insects providing additional evidence of elevated gluconeogenesis due to parasitism. Despite the increased gluconeogenesis in parasitized insects the level of blood sugar was the same in all animals. Because de novo glucose synthesis does not normally maintain blood sugar level in insects maintained under these dietary conditions the findings suggest an aberrant regulation over gluconeogenesis. The 13C labeling in trehalose was nearly symmetric in all insects but the mean C1/C6 13C ratio was higher in parasitized animals suggesting a lower activity of the pentose phosphate pathway that brings about a redistribution of 13C in trehalose following de novo glucose synthesis. Additional studies with insects maintained on a high carbohydrate diet and administered [1,2-13C2]glucose confirmed a decreased level of pentose cycling during parasitism consistent with a lower level of lipogenesis. It is suggested, however, that the pentose pathway may facilitate the synthesis of trehalose from dietary carbohydrate by directing hexose phosphate cycled through the pathway to the production of energy.

Animals↗
PubMed2002

An evolutionary treatment of the morphology and physiology of circulatory organs in insects.

An overview from an evolutionary perspective is presented on the research of the past 2 decades on insect circulatory organs. Based on various functional morphology it is clear that the flow mode of the dorsal vessel ('heart') has changed during the evolution of hexapods. In all apterygotes and mayflies the flow is bidirectional. In most pterygote insects, however, it is unidirectional. In some endopterygote insects, the direction of the flow alternates. This is achieved by heartbeat reversal, which may have various physiological functions and is a derived condition that probably occurred several times during the course of insect evolution. Special attention is given to the hemolymph flow in body appendages. In ancestral hexapods, they are supplied by arteries, whereas circulation in appendages of higher insects is accomplished by accessory pulsatile organs. These auxiliary hearts are autonomous pumps and exhibit a great diversity in their functional morphology. They represent evolutionary innovations which evolved by recruitment of building blocks from various organ systems and were assembled into new functional units. Almost all pulsatile circulatory organs in insects investigated exhibit a myogenic automatism with a superimposed neuronal control. The neuroanatomy of insect circulatory organs has been investigated only in a small number of species but in considerable detail. Numerous potential peptidergic and a few aminergic mediators could be demonstrated by immunocytochemical and biochemical methods. The cardiotropic effectiveness of these mediators may vary among species and it can be stated that there is no uniform picture of the control of the various circulatory organs in insects. A possible explanation for the differences may lie in the different evolutionary origins of the muscular components. Furthermore, insect circulatory organs may represent important neurohemal releasing sites.

Animal Structures↗
PubMed2001

Variable diets and changing taste in plant-insect relationships.

The host ranges of phytophagous insects are determined to a large degree by plant chemistry. Specialist insects are often closely associated with plants that produce characteristic chemicals, which may act as attractants or stimulants to aid in finding or recognizing a host. Generalist insects are generally believed to rely on the presence of repellents or deterrents to ensure avoidance of unsuitable plants. However, the chemistry of any plant can be highly variable, as a result of growth characteristics, genetic variation, or environmental factors. Such variable chemistry may provide windows of opportunity for nonadapted insects to utilize a plant or for a plant to become resistant to a normally adapted herbivore. Differences in insect responses to plant constituents may also result from genetic variation or environmental factors. In particular, dietary experience has been found to influence the ability of insects to taste plant chemicals that may serve as signals of suitability or unsuitability. Certain dietary constituents appear to suppress the development of taste sensitivity to deterrents in an insect, whereas the presence of specific stimulants in the diet may result in the development of dependence on these compounds. These findings further emphasize the fact that the dynamics of plant biochemistry along with plasticity in the sensory system of insects might be expected to play a major role in the evolution of new plant-insect relationships.

Animals↗
PubMed2000

CALNUC (nucleobindin) is localized in the Golgi apparatus in insect cells.

A mouse monoclonal antibody 12B1 was raised against Golgi fractions from Sf21 insect cells and selected as Golgi-specific by immunostaining of the cells. The antigen was purified from the cells by immunoaffinity chromatography with the monoclonal antibody, and its N-terminal and internal amino acid sequences were determined. Based on the partial amino acid sequences, cDNA encoding the antigen protein was cloned and sequenced. The amino acid sequence deduced from the cDNA nucleotide sequence showed a homology to those of CALNUC family proteins, CALNUC (or nucleobindin, a calcium-binding Golgi protein with DNA-binding activity) and protein NEFA (a cell surface protein with DNA-binding, EF-hand, and acidic domains). The insect protein had two EF-hand loops at the same sites as the mammalian CALNUC family proteins, but had no leucine zipper which the mammalian homologues commonly have. An electron microscopic immunoperoxidase study demonstrated that the insect protein was localized in the cis-Golgi cisternae and cis-Golgi networks. Since this localization is identical to that of mammalian CALNUC, the insect protein was considered to be a homologue of CALNUC rather than that of NEFA. Assays involving proteinase K digestion, sodium carbonate extraction and Triton X-114 extraction revealed that the insect CALNUC-like protein was a soluble protein tightly associated with the luminal surface of Golgi membranes as reported for mammalian CALNUC. The insect protein was also shown to have calcium-binding activity as does mammalian CALNUC. These data verify that the insect protein is CALNUC. The existence of CALNUC in insect cells suggests that CALNUC is an essential calcium-binding Golgi protein in a wide range of the animal kingdom. A phylogenetic tree analysis, however, suggested that NEFA was derived from CALNUC long after the segregation of a mammalian ancestor from an insect ancestor.

Acetylglucosaminidase↗
PubMed2001

Radio-frequency and microwave dielectric properties of insects.

Basic principles and definitions of dielectric properties of materials are presented. Data from the literature on the dielectric properties of insects are briefly reviewed and discussed in relation to insect control by selective dielectric heating. Because early measurements of the dielectric properties of insects were taken on bulk samples of insects (insect and air-space dielectric mixtures), a means for converting the dielectric properties, or permittivities, of bulk samples of particulate materials to those of the solid particles is described. The technique uses the Landau & Lifshitz, Looyenga dielectric mixture equation and information on the bulk densities of air-insect mixtures used for dielectric properties measurements along with the densities of the insects. Such converted data for the dielectric constants and loss factors of the insects are presented and collected for comparison with other measurements of insect tissues and permittivity determinations from more recent microwave measurements of these same parameters. Resulting data are presented for reference, and comparisons are presented and discussed briefly.

Animals↗
PubMedDate not supplied

Changes in the rate of CO2 release following feeding in the insect Rhodnius prolixus.

We describe for the first time changes in the rate of CO2 release (as a surrogate of metabolic rate) in the terminal larval stage of the insect Rhodnius prolixus following a blood meal and during the molt leading to the adult stage. These data are presented on a whole-animal basis as well as per gram wet and dry weight. We have also used techniques that allow us to describe the rate of release per gram of actual body tissue (i.e., removing the weight of the remaining bloodmeal in the gut and the metabolically inactive portion of the cuticle). While the metabolic rate of the whole animal rises approximately 10-fold in 15 d following feeding, the rate per gram of dry body mass rises only twofold. We use these data to provide insights into the relative contributions of tissue growth and increases in metabolic intensity to the massive increases in metabolic rate observed in these insects following feeding. Our analyses indicate that the majority of nutrient uptake occurs in the first 4 d following feeding. It is well known in this species that day 4 following feeding is the end of a critical period for the insect in determining whether it will proceed to the next molt. Our results indicate that the insects may be able to make this decision based on nutrients already transported into the body. We examined the "down regulation" of metabolism observed in the latter stages of the molt cycle in this insect. We express these changes on both a per animal and per gram basis and demonstrate that this down regulation extends even into the adult stage before feeding. Using a comparison of the allometric relationships of metabolic rate to mass in insects and ticks, we demonstrate that unfed R. prolixus show a marked decrease in metabolic rate compared to other insects, while fed Rhodnius are similar in metabolic rate to other insects. Rhodnius has a markedly higher metabolic rate (as do all insects) than that found in ticks.

Animals↗
PubMed2006

Genes, enzymes and chemicals of terpenoid diversity in the constitutive and induced defence of conifers against insects and pathogens.

Insects select their hosts, but trees cannot select which herbivores will feed upon them. Thus, as long-lived stationary organisms, conifers must resist the onslaught of varying and multiple attackers over their lifetime. Arguably, the greatest threats to conifers are herbivorous insects and their associated pathogens. Insects such as bark beetles, stem- and wood-boring insects, shoot-feeding weevils, and foliage-feeding budworms and sawflies are among the most devastating pests of conifer forests. Conifer trees produce a great diversity of compounds, such as an enormous array of terpenoids and phenolics, that may impart resistance to a variety of herbivores and microorganisms. Insects have evolved to specialize in resistance to these chemicals -- choosing, feeding upon, and colonizing hosts they perceive to be best suited to reproduction. This review focuses on the plant-insect interactions mediated by conifer-produced terpenoids. To understand the role of terpenoids in conifer-insect interactions, we must understand how conifers produce the wide diversity of terpenoids, as well as understand how these specific compounds affect insect behaviour and physiology. This review examines what chemicals are produced, the genes and proteins involved in their biosynthesis, how they work, and how they are regulated. It also examines how insects and their associated pathogens interact with, elicit, and are affected by conifer-produced terpenoids.

Abietanes↗
PubMed1996

Ecology of insect communities in nontidal wetlands.

Published research about wetland insects has proliferated, and a conceptual foundation about how wetland insect populations and communities are regulated is being built. Here we review and synthesize this new body of work. Our review begins with a summary of insect communities found in diverse wetland types, marshes, forested floodplains, and peatlands. Next, we critically discuss research on the population and community ecology of wetland insects, including the importance of colonization strategies and insect interactions with the physical environment, plants, predators, and competitors. Results from many of the experimental studies that we review indicate that some commonly held beliefs about wetland insect ecology require significant reevaluation. We then discuss the importance of wetland insect ecology for some applied concerns such as efforts to manage wetland insect resources as waterfowl food and development of ecologically sound strategies to control pest mosquitoes. We conclude with a discussion of wetland conservation, emphasizing insect aspects.

Journal Article↗
PubMed1997

Insect tolerance to a neurotoxic polypeptide: pharmacokinetic and pharmacodynamic aspects

Androctonus australis insect toxin (AaIT) is an insect-selective neurotoxic polypeptide from scorpion venom used to probe insect Na+ channels and to design insecticidal recombinant baculoviruses. When injected into susceptible insects (such as flies or cockroaches), nanogram doses of the toxin induce a rapid paralysis within seconds. More tolerant insects respond to microgram doses by developing either a slow progressive paralysis, as in lepidopterous larvae, or a rapid but reversible paralysis, as in Trachyderma philistina, a tenebrionid beetle. Using toxicity and binding assays, microscopy and chromatography, we show that the tolerance of insects to AaIT occurs at both the pharmacokinetic and pharmacodynamic levels. Pharmacokinetic effects occur in Trachyderma philistina in which the toxin undergoes a progressive process of degradation and elimination from the hemolymph, resulting in the loss of 95­97 % of toxin activity 6 h after injection. The pharmacodynamic aspect was demonstrated in studies of the kinetics of binding dissociation of [125I]AaIT from neuronal membranes of susceptible and tolerant insects. Stable binding is shown in susceptible insects such as cockroaches and locusts, which have a dissociation half-time of approximately 9 and 5 min, respectively. This contrasts strongly with the fast half-time of dissociation of 7 s for Spodoptera littoralis larvae and 9 s for Trachyderma philistina, which are both relatively tolerant to AaIT. These differences in binding kinetics may reflect a structural and functional diversity of Na+ channels in different insects that is responsible for their diverse susceptibility to neurotoxic polypeptides.

Journal Article↗
PubMed2006

Forest age influences oak insect herbivore community structure, richness, and density.

Plant succession is one of many factors that may affect the composition and structure of herbivorous insect communities. However, few studies have examined the effect of forest age on the diversity and abundance of insect communities. If forest age influences insect diversity, then the schedule of timber harvest rotation may have consequent effects on biodiversity. The insect herbivore community on Quercus alba (white oak) in the Missouri Ozarks was sampled in a chronoseries, from recently harvested (2 yr) to old-growth (approximately 313 yr) forests. A total of nine sites and 39 stands within those sites were sampled in May and August 2003. Unique communities of plants and insects were found in the oldest forests (122-313 yr). Density and species richness of herbivores were positively correlated with increasing forest age in August but not in May. August insect density was negatively correlated with heat load index; in addition, insect density and richness increased over the chronoseries, but not on the sunniest slopes. Forest structural diversity (number of size classes) was positively correlated with forest age, but woody plant species richness was not. In sum, richness, density, and community structure of white oak insect herbivores are influenced by variation in forest age, forest structure, relative abundance of plant species, and abiotic conditions. These results suggest that time between harvests of large, long-lived, tree species such as white oak should be longer than current practice in order to maintain insect community diversity.

Animals↗