The extraordinary abundance of ants in tropical rainforest canopies has led to speculation that numerous arboreal ant taxa feed principally as "herbivores" of plant and insect exudates. Based on nitrogen (N) isotope ratios of plants, known herbivores, arthropod predators, and ants from Amazonia and Borneo, we find that many arboreal ant species obtain little N through predation and scavenging. Microsymbionts of ants and their hemipteran trophobionts might play key roles in the nutrition of taxa specializing on N-poor exudates. For plants, the combined costs of biotic defenses and herbivory by ants and tended Hemiptera are substantial, and forest losses to insect herbivores vastly exceed current estimates.

Objective: This study was designed to assess physicians’ attitudes toward obese patients and the causes and treatment of obesity. Research Methods and Procedures: A questionnaire assessed attitudes in 2 geographically representative national random samples of 5000 primary care physicians. In one sample (N = 2500), obesity was defined as a BMI of 30 to 40 kg/m2, and in the other (N = 2500), obesity was defined as a BMI > 40. Results: Six hundred twenty physicians responded. They rated physical inactivity as significantly more important than any other cause of obesity (p < 0.0009). Two other behavioral factors—overeating and a high‐fat diet—received the next highest mean ratings. More than 50% of physicians viewed obese patients as awkward, unattractive, ugly, and noncompliant. The treatment of obesity was rated as significantly less effective (p < 0.001) than therapies for 9 of 10 chronic conditions. Most respondents (75%), however, agreed with the consensus recommendations that a 10% reduction in weight is sufficient to improve obesity‐related health complications and viewed a 14% weight loss (i.e., 78 ± 5 kg from an initial weight of 91 kg) as an acceptable treatment outcome. More than one‐half (54%) would spend more time working on weight management issues if their time was reimbursed appropriately. Discussion: Primary care physicians view obesity as largely a behavioral problem and share our broader society's negative stereotypes about the personal attributes of obese persons. Practitioners are realistic about treatment outcomes but view obesity treatment as less effective than treatment of most other chronic conditions.

In numbers and biomass, ants (Hymenoptera, Formicidae) often dominate arthropod faunas of tropical rainforest canopies. Extraordinary ant abundance is due principally to one or a few species able to tap the high productivity of canopy foliage by feeding on plant and homopteran exudates. Prior studies of nitrogen isotopic ratios show that exudate-feeders derive much of their nitrogen (N) by processing large quantities of N-poor, but carbohydrate (CH0)-rich, exudates. CHOs in excess of those that can be coupled with protein for growth and reproduction (postulated as the colony's first priorities) may be directed at little cost and some profit to functions that increase access to limiting protein. High dietary CH0:protein ratios for exudate-feeders appear to subsidize 'high tempo' foraging activity, defence of absolute (level 111) territories, and production of N-free alarm/defence exocrine products that enhance ecological dominance in contests with other ants. Among organisms (e.g. plants and Lepidoptera) symbiotic with ants, CH0:protein ratios of ant rewards may control both the identities of ant associates and the quality of ant-rendered services. Dietary ratios of CH0:protein play an important and previously unrecognized role in the ecology and evolution of ants generally. Modifications of worker digestive systems in certain ant subfamilies and genera represent key innovations for handling and processing large volumes of liquid food. The supreme tropical dominants are species released from nest site limitation and able to place their nests in the vicinity of abundant exudate resources. Polydomy appears to be typical of these species and should produce energetic savings by taking colony fragments to the resource. 0 1997 The I . I I I I I~~I I S o t i~t y of Inindon ADDITIONAL KEY WORDS:-ant-plant interactionscanopy samplesexocrine chemistry foraging tempo ~ Homopteralycaenoid butterfliesproventticulusresource balance model symbioses ~ temtoriality.