James E. Carrel

Cantharidin Biosynthesis and Function in Meloid Beetles

Publisher Summary Cantharidin, a teφenoid substance found in blister beetles, is among the most widely known insect natural products in the world. Its reputation derives principally from descriptions of its physiological activities, most notably as an aphrodisiac for humans and livestock, that are traced from oral history. Cantharidin is also the blistering agent that earned these bettles their common name. These diverse effects on humans are paralleled by activities that the beetles exploit in their reproduction and ecology. The chapter explores the latter perspective of cantharidins role—the pheromonal and other adaptive functions of cantharidin in blister beetles. The chapter discusses the chemical and biosynthetic knowledge of cantharidin to build a foundation for understanding its ecological roles in blister beetles. The intriguing simplicity of the cantharidin structure belies not only the difficulties encountered establishing the details of its molecular structure but also the complexity of the metabolic process involved in its formation by blister beetles. Comparison of its structure to those of known metabolic origin readily suggests that this compound belongs to the terpenoid biosynthetic class of natural products.

Heart Rate and Physiological Ecology

A spider’s heart rate is a major indicator of its physiological state (Mikulska 196lb). Unfortunately, this concept is more an extrapolation from studies with a wide variety of nonarachnid invertebrates and vertebrates than it is a conclusion drawn from studies with spiders themselves. For example,J.C. Jones et al. (1971) and Ligon and Greenberg (1971) summarized data showing that heart rate in a generalized invertebrate varies according to the properties of the individual, its environment, and the experimental methodology used to gather data. However, of the 100 or so publications cited by them, some of which date back as far as 1837, none ostensibly deals with spiders.

Instability of sandy soil on the Lake Wales Ridge affects burrowing by wolf spiders (Araneae: Lycosidae) and antlions (Neuroptera: Myrmeleontidae).

Tests with Geolycosa spiders revealed that these arachnids may be excluded largely from the Ridge Sandhill-turkey oak ecosystem on the Lake Wales Ridge because their burrows quickly collapse in the unstable natural soil (Astatula sand). Comparable results were obtained in tests of pit construction by antlion larvae (Myrmeleontidae), which may serve as bioindicators of soil stability.

Sex-Specific Food Preferences in the Madagascar Hissing Cockroach Gromphadorhina portentosa (Dictyoptera: Blaberidae)

INTRODUCTIONFor most insects, adult nutrition affects not only survival of individuals butalso their reproductive output. In particular, fecundity of females commonlydepends on ingestion of protein necessary for egg development, whereasmale fertility is not highly protein dependent (Chapman, 1982; House, 1974;Engelmann, 1999). Furthermore, because insects generally are unable toconvert lipids to monosaccharides (Bignell, 1981), carbohydrates and pro-teins serve as primary energy sources in both sexes (House, 1974).Recentstudiesrevealthatanumberofinsectsexhibitsex-specificdiffer-ences in feeding behavior that are correlated with adult nutritional require-ments. For example, young female tephritid fruit flies (Diptera: Tephritidae)that are protein-hungry are more attracted to odors of protein food baitsthan to odors of host fruit, whereas males and protein-fed females areattracted more toward fruit odors (Cornelius

POPULATION DYNAMICS OF THE RED WIDOW SPIDER (ARANEAE: THERIDIIDAE)

Populations of the red widow spider, Latrodectus bishopi, in native Florida scrub at the Archbold Biological Station were monitored annually on ten ≈0.5 ha transects in late winter from 1987 to 2000. Of 398 L. bishopi detected in the study, all but three had their silken retreats built in palmetto leaves. L. bishopi at rest in retreats in saw palmetto (Serenoa repens) were higher above the ground (≈0.5 m) than spiders in scrub palmetto (Sabal etonia) (≈0.3 m). From a peak of 31 spiders/ha in 1989, the average L. bishopi density declined exponentially to only 0.3 spiders/ha in 1997, after which L. bishopi densities began to recover. Burning of scrubby transects in spring or summer appeared to have no affect on subsequent L. bishopi populations. There were no significant correlations between L. bishopi population density and local temperature or precipitation data. These results suggest that undescribed biotic factors may regulate populations of the red widow spider in a density-dependent fashion.

Ant Species in the Diet of a Florida Population of Eastern Narrow-Mouthed Toads, Gastrophryne carolinensis

Abstract Gastrophryne carolinensis (Eastern Narrow-mouthed Toad) is known to be an ant specialist, but prey identification has rarely progressed beyond family level. There are no prey records from Florida scrub, a rare upland habitat type. This study identifies species of 4859 individual ants retrieved from stomachs of 146 G. carolinensis collected in Florida scrub. All toads had consumed ants; ants comprised about 95% of all food items. Forty-three species of ants were recorded. About 77% were various species of Pheidole or Nylanderia. The ants consumed were mostly small (4 mm or less in length) and nocturnally active. Species that were eaten belong to ant genera known to contain venoms, chemical repellents, or other organic substances in exocrine glands. This finding suggests the possibility that Narrow-mouthed Toads have opportunities to sequester exocrine secretions of ants, in the manner of some other anurans. The diversity of ant species consumed by G. carolinensis suggests that this species might be able to subsist on disturbed-site ants, including exotic species such as Solenopsis invicta.

Defensive secretion of the pill millipedeGlomeris marginata. I. Fluid production and storage

AdultGlomeris marginata reloaded glandular defensive fluid slowly and fairly constantly at 15 °C for 100 days after being milked to depletion. Female millipedes produced more sticky exudate than males, but the two sexes stored secretion at approximately the same absolute rate, 12 μg/individual/day. Hence, males, which weighed one third as much as females, accumulated disproportionately more secretion. MaleGlomeris in the reloading treatments after 75 days yielded as much exudate as controls, millipedes given 100 days to supplement their field reserves, whereas experimental females always produced less secretion than controls. Projections from these data suggest that adultGlomeris, regardless of sex, require more than 4 months to replenish their defensive reserves after completely discharging them in an attack.

Relationship between Diet and Microhabitat Use of Red-legged Salamanders (Plethodon shermani) in Southwestern North Carolina

The selection of a foraging habitat may be driven by food availability or by the cost associated with the use of that habitat. This basic tradeoff can lead individuals in the same population to occupy different habitats in response to perceived risk levels. In the southeastern United States, plethodontid salamanders are often observed climbing vegetation, which represents a potential foraging habitat. We examined whether diet composition of the Red-legged Salamander, Plethodon shermani, differed between salamanders found on vegetation and on the ground surface. Contrary to the results of a previous study, we found that the overall number and mass of prey items did not differ between salamanders in these two microhabitats. Furthermore, we found no evidence that the relative use of different prey categories varied in relation to a salamanders selected microhabitat. Although salamanders of all body sizes had consumed a diverse range of prey items, we found evidence of an ontogenetic shift in prey utilization, with smaller salamanders consuming a significantly greater number of prey items than larger salamanders while there was no relationship between body size and mass of prey consumed.

Differential survival of Geolycosa xera archboldi and G. hubbelli (Araneae, Lycosidae) after fire in Florida scrub

Abstract A replicated pre- and post-burn study of survival of small and large Geolycosa xera archboldi McCrone 1963 and G. hubbelli Wallace 1942 in Florida scrub was conducted. These two syntopic species were chosen because G. x. archboldi prefers large gaps of barren sand in the scrub matrix, sites with little fuel for fires, whereas G. hubbelli strongly favors small gaps having some leaf litter, sites with modest or high fuel-loads. On the basis of these species-specific differences in microsite characteristics, I hypothesized that G. x. archboldi would be very fire tolerant but that G. hubbelli would be fire intolerant. I established two size classes for the Geolycosa: small spiders had 3–5 mm diameter × 5–9 cm deep burrows; large spiders had > 6 mm diameter × 10–17 cm deep burrows. Burrows of 25 spiders in each species × size class were marked before a burn in seven burn units (= fire management areas) and survival or mortality of each occupant was ascertained over the course of 5 days post-burn. Thus, the experimental design was 2 species × 2 size classes × 7 burn units × 25 replicates/burn unit (n = 700 spiders total). Survivorship was very high in small and large G. x. archboldi and in large G. hubbelli (93–96%), but it was low in small G. hubbelli (35%). Temperature recordings suggest mortality in small G. hubbelli was caused by high temperatures at depths of 5–10 cm during intense, but brief burns that characterize fires in Florida scrub. In contrast, large G. hubbelli had burrows sufficiently deep so that most of them did not experience lethal temperatures during burns.

Defensive secretion of the pill millipedeGlomeric marginata

AdultGlomeris marginata reloaded glandular defensive fluid slowly and fairly constantly at 15 °C for 100 days after being milked to depletion. Female millipedes produced more sticky exudate than males, but the two sexes stored secretion at approximately the same absolute rate, 12 μg/individual/day. Hence, males, which weighed one third as much as females, accumulated disproportionately more secretion. MaleGlomeris in the reloading treatments after 75 days yielded as much exudate as controls, millipedes given 100 days to supplement their field reserves, whereas experimental females always produced less secretion than controls. Projections from these data suggest that adultGlomeris, regardless of sex, require more than 4 months to replenish their defensive reserves after completely discharging them in an attack.