How to know the spiders

v, 220 p.; 22 cm

Body condition helps to explain metabolic rate variation in wolf spiders

1. Metabolism is the fundamental process that powers life. Understanding what drives metabolism is therefore critical to our understanding of the ecology and behavior of organisms in nature. 2. Metabolic rate generally scales with body size according to a power law. However, considerable unexplained variation in metabolic rate remains after accounting for body mass with scaling functions. 3. We measured resting metabolic rates (oxygen consumption) of 227 field-caught wolf spiders. Then, we tested for effects of body mass, species, and body condition on metabolic rate. 4. Metabolic rate scales with body mass to the 0.85 power in these wolf spiders, and there are metabolic rate differences between species. After accounting for these factors, residual variation in metabolic rate is related to spider body condition (abdomen:cephalothorax ratio). Spiders with better body condition consume more oxygen. 5. These results indicate that recent foraging history is an important determinant of metabolic rate, suggesting that although body mass and taxonomic identity are important, other factors can provide helpful insights into metabolic rate variation in eco-logical communities

Novel male trait prolongs survival in suicidal mating

Male redback spiders (Latrodectus hasselti) maximize paternity if they copulate twice with their cannibalistic mate. Facilitating cannibalistic attack during their first copulation yields paternity benefits. However, females have paired sperm-storage organs inseminated during two separate copulations, so males that succumb to partial cannibalism during the first copulation lose at least 50% of their paternity to rivals. In this paper, we describe a novel male trait—an abdominal constriction that appears during courtship—that allows males to survive and mate with females for a second time, despite the substantial cannibalistic damage inflicted during the first copulation. Constricted males that were wounded to simulate early cannibalism had higher endurance, greater survivorship, longer subsequent courtship and higher mating success than wounded males that were not constricted. Constriction was not found in a non-sacrificial congener that rarely survived simulated cannibalism, and the protective effect of constriction in redbacks was specific to the type of damage inflicted by females during the first copulation. Thus, the abdominal constriction allows males to overcome the potential fitness limit imposed by their own suicidal strategy—paradoxically, by prolonging survival across two cannibalistic copulations

Distribution and importance of spiders inhabiting a Brazilian sugar cane plantation

The spider fauna (Araneae) of a sugar eane plantation was surveyed monthly by hand colteetion and beating vegetation in sugar cane fields across Botucatu, State of São Paulo, Brazil. Composition and rchness (family and species where identifieation to species was possible) microhabitat preferenees were reeorded, and diversity and evenness indices were calculated. A total of 1291 spiders belonging to 73 species and 20 families were collected. The most diverse families were Theridiidae, Salticidae, and Araneidae, and the most abundant ones were Theridiidae, Saltieidae, Anyphaenidae, and Araneidae, Seven species represented 58.6% of the total fauna, with Crysso pulcherrima (Mello-Leitão,1917) (Theridiidae) composing 28.2%. About 65% of the spiders occupied the upper part of the plants (above 20 cm). Five spider species were present in the sugar cane throughout crop development. Evidence of spiders feeding on sugar cane pest species was observed

Comportamento e dieta alimentar de uma espécie de Latrodectus do grupo Mactans (Araneae, Theridiidae) em cativeiro Behavior and diet supply of Latrodectus group Mactans (Araneae, Theridiidae) in captivity

<abstract language="eng">Latrodectus gr. mactans is responsible for 28% of ali accidents provoked by spiders in state of Bahia, Brazil (1980-1990), which makes necessary the study of its manejament. The spiders were captured in Ondina, Salvador, and in Baxio, Esplanada (Bahia, Brazil); they were mantained in captivity, with food supply weekly (Atta sp., larva of Tenebrio sp. and Drosophila melanogaster) with three hours/ offers observation time, during march/95 to april/96. In captivity, the spiders accepted two kinds of food: Atta sp., which seems to be the major item of its diet in natural conditions, and larva of Tenebrio sp., which is not available in natural conditions. Drosophila melanogaster was systematically rejected. The feeding behavior iscomposed by four distinct steps: (1) imrnobilization, (2) inoculation, (3) second immobilization and (4) ingestion. Two kinds of social alimentary behavior are descri-bed. The results indicated that larvae of Tenebrio sp. can be an alternative supply for successfull maintenance of this specie in captivity