Amy Berkov

Neotropical tree species and their faunas of xylophagous longicorns (Coleoptera: Cerambycidae) in French Guiana

Estimates of the total number of species in existence are based, in part, upon assumptions about the host specificity of tropical insects. These estimates are difficult to evaluate because there is so little data available describing the host-plant affiliations of tropical insects. Over a three-year period, 690 trees in the Sinnamary River Basin of French Guiana were felled and investigated for their associated cerambycid fauna. These trees (belonging to approximately 200 species representing 38 plant families) ultimately gave rise to 334 species of cerambycids. One-quarter of these beetle species had not yet been described, and hundreds of previously unknown host-plant associations were documented. These data are presented in a table which also includes the results of additional rearing experiments in French Guiana, as well as selected literature references. Organized by host-tree family, the table facilitates the circumscription of beetle guilds occurring on related hosts. Abundantly represented plant families typically gave rise to faunas including numerous taxonomically unrelated beetles. The beetle guilds associated with different plant families had very different ratios of specialist:generalist species. The majority of the specialists successfully reproduced in related tree species belonging to a particular plant family; only a few cerambycid species appear to depend exclusively on a single host. These data contribute to an understanding of host specificity and host fidelity in tropical insects.

Convergent evolution in the antennae of a cerambycid beetle, Onychocerus albitarsis, and the sting of a scorpion

Venom-injecting structures have arisen independently in unrelated arthropods including scorpions, spiders, centipedes, larval owlflies and antlions, and Hymenoptera (wasps, ants, and bees). Most arthropods use venom primarily as an offensive weapon to subdue prey, and only secondarily in defense against enemies. Venom is injected by biting with fangs or stinging with a specialized hypodermic structure used exclusively for the delivery of venom (usually modified terminal abdominal segments). A true sting apparatus, previously known only in scorpions and aculeate wasps, is now known in a third group. We here report the first known case of a cerambycid beetle using its antennae to inject a secretion that causes cutaneous and subcutaneous inflammation in humans. Scanning electron microscopy revealed that the terminal antennal segment of Onychocerus albitarsis (Pascoe) has two pores opening into channels leading to the tip through which the secretion is delivered. This is a novel case of convergent evolution: The delivery system is almost identical to that found in the stinger of a deadly buthid scorpion.

Neotropical soldier flies (Stratiomyidae) reared from Lecythis poiteaui in French Guiana: Do bat-pollinated flowers attract saprophiles?

Abstract Two species of Stratiomyidae, Ptecticus nigrifrons Enderlein and Ptecticus sp., were reared from fallen androecia of Lecythis poiteaui Berg (Lecythidaceae) at rain forest sites in French Guiana. Floral aromas were collected by headspace adsorption from the night-blooming flowers. Gas chromatography-mass spectrometry analysis (GC-MS) identified several sulfur-containing compounds that contribute to the characteristic foul odor of the flowers. Although stratiomyids are thought to be generalist associates of decaying matter of plant and animal origin, we suggest that fetid floral attractants may make L. poiteaui flowers especially attractive to certain flies. This is the first report of Lecythidaceae flowers hosting stratiomyid flies.

Redescription of Manicocoris rufipes (Fabricius 1787), including nymphs I, II, III, and V (Reduviidae: Harpactorinae: Apiomerini), and its association with Clusia fruits

The genus Manicocoris and its only species, M. rufipes, are described and illustrated, including nymphal instars I, II, III, and V. Descriptions include morphological and morphometrical characters. This article also provides a new record of an association between M. rufipes and the fruits of Clusia grandiflora Splitg. In French Guiana, adult specimens and nymphal instars II and III of M. rufipes were collected within fallen C. grandiflora fruits, where they awaited prey with their raptorial forelegs coated with a sticky fruit-derived substance.

Niches of Saproxylic Weevils (Coleoptera: Curculionidae) in French Guiana

ABSTRACT The loss of tropical forests has a direct effect on saproxylic beetles through the loss of larval feeding substrates and an indirect effect through microclimate change in forest fragments. Impacts will be exacerbated by climate change, and species with narrow niches will be particularly vulnerable. This study presents baseline data on niches (seasonality, host plant, stratum, and branch diameter) of saproxylic weevils in a minimally disturbed moist forest of French Guiana. Weevils (excluding bark beetles) were expected to be host specialists and more abundant in moist microhabitats. Bait branches from three species in the Brazil nut family (Lecythidaceae) were exposed during the dry and rainy season at ground and canopy stratum. They yielded 1,262 weevils in 24 species; 95% belonged to the subfamily Conoderinae. Weevils emerged in greatest abundance from Eschweilera coriacea (A. P. de Candolle) S. A. Mori and from branches in the coolest, moistest microhabitat: ground stratum during the rainy season. Shifts towards warmer, drier climatic conditions would probably have a negative impact on most saproxylic weevil species currently associated with the Brazil nut family. Although this family is expected to suffer under biotic homogenization, the favored host species is hyperdominant throughout Amazonia; climate permitting, E. coriacea could provide a refuge.

Senescent Neotropical flowers (Lecythidaceae) offer a rich nutrient source to ground-foraging arthropods1,2

Abstract Forest floor litter communities include detritivorous, predacious, and parasitic arthropods that feed on, or forage within, the decaying organic material. Although this substrate is heterogeneous, little research has investigated the preferential feeding tendencies of these arthropods. The objective of this study, conducted in the lowland rain forest of French Guiana, was to examine some of the factors that may influence foraging behavior. Plots were covered with either leaf or floral litter from three species of Lecythidaceae (Brazil nut family), and traps were set within and above each plot. Traps baited with floral litter yielded significantly more arthropods than those baited with leaf litter. Floral and leaf tissues were subsequently analyzed for moisture, fiber, sugar and nutrient concentrations. These analyses indicate that, relative to leaf litter, floral litter provides a quantitatively richer nutrient source available at lower energy expenditure, suggesting that these arthropods (mostly insects) may be operating under optimal foraging strategy.

Seasonality and Stratification: Neotropical Saproxylic Beetles Respond to a Heat and Moisture Continuum with Conservatism and Plasticity

Insect niche breadth informs community assembly and impacts the resilience of populations, species, and ecosystems. Niches are poorly known for most tropical insects, especially concealed feeders associated with tall trees. This chapter synthesizes data regarding seasonality and stratification in the early colonists of moribund wood, Cerambycidae and saproxylic Curculionidae. These data, from five rearing experiments conducted at four Neotropical moist forest sites over two decades, are of particular value because they can be used to generate predictions in an unpredictable time. Beetle species currently associated with warmer, drier, microhabitats (in the subfamily Cerambycinae and some Curculionidae) might withstand drier conditions, but not necessarily higher temperatures. Those currently associated with relatively cool, moist microhabitats (most Curculionidae) may be more vulnerable to changes in the length and severity of the dry season. Rather than characterizing tropical saproxylic insects by their periods of adult activity or flight height, which can be variable, it would be useful to conceptualize them with preferences along a continuum, from warm and dry to cool and moist.