Three aromatic juvenoids (fenoxycarb, JH-286 and a new pyrazole analog) were evaluated for morphogenetic, chromotropic, morphometric and prothoracicotropic activities on the American grasshopper, Schistocerca americana (Drury), and their activities compared with those of commercial methoprene and synthetic JH-III. Fenoxycarb, the most active insect growth regulator examined, was found to induce a significant mortality in developing nymphs and caused severe morphogenetic damage during ecdysis to the adult. Juvenoid treatment were also observed to promote some overaged nymphs and to induce chromotropic changes in both the cuticle and hemolymph pigmentation. Except for a reduced larvicidal action, similar levels of activity were obtained when fenoxycarb was tested on the desert locust, Schistocerca gregaria (Forskal). The chromoproteins responsible for the green coloration characteristic of the hemolymph of S. americana and S. gregaria were isolated and characterized. Hemolymph from last instar nymphs and adults of S. americana was characterized by the presence of yellow lipophorin (Lp), a green chromoprotein (G-P), and two cyanoproteins (Cp-I and Cp-II). Treatment with fenoxycarb enhanced the concentration of the two cyanoproteins in nymphs and adults, and induced the appearance of a third cyanoprotein (Cp-F) in nymphs. Hemolymph from last instar nymphs of S. gregaria was characterized by the presence of yellow lipophorin (Lp) and two blue cyanoproteins (HCp and LCp), whereas only Lp and LCp were present in adults. Treatment with fenoxycarb increased the concentration of both cyanoproteins in nymphs, but only of LCp in adults. The non-steroidal ecdysone-agonist 2RH-5849 (1,2-dibenzoyl-1-tert-buthyl-hydrazine) was found to be an effective neuropoison when injected on S. americana. Treated grasshoppers became immediately hyperactive, followed by loss of coordination, paralysis and eventually death. We discovered that this insect growth regulator also induced bilateral autotomy of the methatoracic legs. However, no evidence of ecdysonergic or morphogenetic activities were found. Synergism studies with neurotoxins of known mode of action suggested that RH-5849 has a mechanism of action similar to that of 4-amino pyridine, which blocks potassium channels.

A rapid clearance of a third of the number of Onchocerca lienalis microfilariae injected into Simulium vittatum, a laboratory host, occurred within 2 hr post inoculation (pi) regardless of dose. A second injection, 2.5 hr after the first, resulted in a lower proportion of microfilariae eliminated, suggesting that availability of active factors were reduced after the first inoculation. Microfilariae did not differ in their susceptibility to clearance as microfilariae that were recovered 2 hr pi and reinoculated into other flies were eliminated faster than unexposed controls. In S. jenningsi, a natural vector, rapid microfilariae clearance occurred similarly and many immotile microfilariae were observed (> 85% at 12 hr pi). Rapid clearance and immobilization of microfilariae represent newly-described immune responses to macroparasites of black flies. Migration of O. lienalis microfilariae into the thorax of S. vittatum proceeded in 2 phases: 0-2 and 6-12 hr pi. Migration success 12-24 hr pi was only 36%, indicating that a large proportion of microfilariae failed to reach the thorax. Migration success was density independent. Microfilariae that arrived into the thorax within 2 hr pi had similar migration potential to microfilariae that remained in the abdomen at this time. The number of microfilariae in the thorax at each time point, but not the proportion of microfilariae in the thorax, was negatively correlated with microfilariae loss, suggesting that microfilariae loss affected migration success. The behavioral responses of O. lienalis microfilariae to tissue factors of S. vittatum, were studied using a novel in vitro bioassay. Microfilariae accumulated towards thoracic tissues at densities 4 times higher than towards abdominal tissues. Microfilariae directed themselves toward the thorax rather than arresting their movement after they make contact with thoracic tissues as contact with thoracic tissues was not necessary. Chemical cue(s) provided principal guidance for microfilariae to locate thoracic tissues. Microfilariae lost their ability to differentiate between thoracic and abdominal tissues and reversed their differential response following experimental manipulation in chemical cue(s) distribution. Exposure of thoracic tissue increased its attractiveness but intact thorax attracted more microfilariae than excised abdomen. Abdominal tissue did not affect thorax attractiveness. Involvement of a large molecular weight protein(s) was suggested.

The effects of sunflower (Helianthus annuus) and groundcherry (Physalis pubescens), two hosts of the tobacco budworm (Heliothis virescens), on predation by paper wasps (Polistes arizonensis) were examined. Initially it was found that P. arizonensis foragers took more caterpillars from H. annuus plants than P. pubescens in paired-choice tests. Regarding physical aspects of the plants, wasps took longer to locate prey on artificial plants with higher leaf surface areas and gave up searching faster on artificial plants with more complex architectures. In paired-choice tests for chemical effects, wasps chose more caterpillars within H. annuus odor than in P. pubescens odor. They also chose more H. annuus-reared larvae than P. pubescens-reared larvae when they were presented without plants. Predator handling times were affected by the amount of food in the caterpillar gut, with a slight trend depending on what plant species was present in the caterpillar gut.

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<p> Anthropogenic trampling affects soil and litter-dwelling invertebrate communities in southern California parks, potentially altering community dynamics and hindering nutrient cycling in coastal oak woodland habitats. I collected meso- and macro-faunal community data from leaf litter and soil in frequently and infrequently trampled areas of six San Diego and three Orange County parks during fall 2011 and spring 2012. I recorded relative compaction, moisture percentage and litter mass then extracted eight soil monoliths at each park (25cm x 25cm x 5cm depth) and the detritus above them. I hypothesized frequently trampled invertebrate communities would show decreased abundance, richness and diversity and altered assemblages compared to infrequently trampled communities. Low impact areas showed higher richness and diversity in the soil layer in fall and leaf litter layer in spring. In the laboratory, I hypothesized Lumbricus terrestris earthworms would be more active, creating more large water-stable soil aggregates in low compaction treatments but found no effect of compaction on soil aggregates.</p>

<p> Fire is an important tool in the sustainable management of ecosystems at global and local scales. In addition to increasing biodiversity, fire has been shown to decrease exotic species invasion, promote growth of commercially and ecologically important trees, and reduce risk of wildfire. Missouri has a long history of anthropogenic and naturally induced fire aiding the establishment of oak and pine-dominated woodlands and savannas. Fire has been reintroduced through forest management in the region after a period of fire suppression to help retain oak-dominance in forests throughout Missouri. Research on the effects of fire is ample for many wildlife species and plants but virtually excludes insects including ants, especially in Missouri and most of the United States. Ants are considered ecosystem engineers for their contribution to soil turnover, aeration and chemical and structural modification and are important seed dispersers. The effects of prescribed burning on ant assemblage diversity, abundance, composition and function were examined in oak-hickory and oak-pine forests in the Missouri Ozark Highlands. Where fire was present annually for over sixty years, ant abundance, Generalized Myrmicinae, soil and litter nesters and small ants increased. Fire every four years for over sixty years resulted in higher Shannon diversity, Cryptic Species, litter nesters and small and medium ants. In addition, this treatment shared ants with both the control and annually burned plots. Control plots were dominated by Subordinate Camponotini, Cold Climate Specialists, wood nesters and medium sized ants. Ants were also assessed after just two fires over the course of ten years. Five and six years after fire ant assemblages were more affected by topographic position than by prescribed burning. Ant assemblages of burned and unburned sites were homogenous when compared using a Morisita Similiarity index. When comparing these treatments to those that have been burned for over sixty years using the Similarity index, both were more similar to the control. In summary, long term fire implementation results in more lasting changes in ant communities because habitat alteration is maintained over time. Habitat heterogeneity produces a more diverse assemblage of ants at the landscape scale and hence higher functional diversity. Finally, categorization of ant communities may simplify ant sampling so that the natural history of each species need not be known in order to assess ecological effects of ant assemblages associated with burn treatments.</p>

The planthopper Prokelisia marginata is the most common insect herbivore in the salt marshes of northwestern Florida, where it feeds and reproduces on smooth cordgrass, Spartina alterniflora Loisel. Relative to other sites where it has been studied, population densities of this planthopper in north Florida are low, despite high fecundity. Low nymphal survivorship, combined with high rates of adult mortality and dispersal, rapidly diminish the densities of local populations. Many factors act to alter the dynamics of planthopper populations. This study was designed to determine the magnitude of the effect of several of these factors on the demography and population dynamics of Prokelisia marginata at Apalachee Bay, Florida. / A field experiment looked at the impact of tides on planthopper populations. Artificial islands were used to create patches of the host plant. Floating islands were used to eliminate tidal inundation and waves, while populations on other islands experienced natural tidal conditions. Analysis showed that the populations did not differ significantly in size throughout the experiment and that they had similar dynamics. In the laboratory, simulated tidal inundation experiments showed that Prokelisia marginata is behaviorally adapted to withstand tidal submergence, either by retreating from the tide or by becoming submerged, and that the planthoppers are able to survive long periods under water. / A second field experiment examined the effects of spider predation on populations of Prokelisia marginata. Nymphal populations were significantly reduced in the presence of spiders, but adults were unaffected. Thus, spider predation had no effect on the population as a whole. A laboratory experiment showed that nymphs are more susceptible than adults to direct predation, and that the presence of spiders alters their life history. / The most important factor acting to reduce adult densities appears to be dispersal of the insects away from their populations. Because most of the dispersing insects probably fail to locate new sites on which to reproduce, dispersal is an important factor acting to reduce populations of Prokelisia marginata in northwestern Florida. / Source: Dissertation Abstracts International, Volume: 50-12, Section: B, page: 5443. / Major Professor: Donald R. Strong. / Thesis (Ph.D.)--The Florida State University, 1989.

The biology and foraging behavior of the fairyfly parasitoid Anagrus delicatus (Hymenoptera: Mymaridae) were studied to determine their effect on host population dynamics and stability. Anagrus delicatus is a short-lived solitary parasitoid that attacks the egg stage of two geographically sympatric planthoppers, Prokelisia marginata and P. dolus (Homoptera: Delphacidae). Host eggs are laid within the leaves of the grass, Spartina alterniflora, found in salt-marshes of the Atlantic and Gulf coasts of the eastern United States. / Laboratory studies indicate that upon locating a patch (S. alterniflora leaves), A. delicatus quickly and efficiently detects the presence of host eggs. Wasps remain on a patch for up to ten hours, but numbers of hosts attacked are low and variable and not much affected by host density. This low attack rate is not a consequence of differences among host species, parasitoid egg limitation, long handling times, a high ratio of parasitized to unparasitized hosts, or the presence of a host refuge. However, direct interference among parasitoids does cause a decrease in number of attacks as wasp density per patch increases. These behaviors lead to density-independent parasitism among S. alterniflora leaves. / Field studies that measured the response of natural populations of A. delicatus to experimental host patches corroborate these laboratory findings. Per capita numbers of hosts parasitized are low, variable, and a declining function of parasitoid density (parasitoid interference); and result in spatial and temporal density independence. Wasps appear to favor a foraging strategy that serves to spread eggs among a number of host patches. / I examined these parasitoid behaviors for their effect on stability in traditional host-parasitoid models. In general, patch use by A. delicatus is not stabilizing, but parasitoid interference can greatly enhance or cause interaction stability. A model developed specifically for this system that incorporates both host and parasitoid biology and behavior supports this conclusion. Due to parasitoid interference and asynchrony in host and parasitoid generation times, this model predicts that A. delicatus will cause the host population to exhibit "stable" cycles through time; exactly the pattern found in nature. / Source: Dissertation Abstracts International, Volume: 52-10, Section: B, page: 5069. / Major Professor: Joseph Travis. / Thesis (Ph.D.)--The Florida State University, 1991.