Both sexes of the bark beetle Dendroctonus brevicomis convert the (+) and (-) enantiomers of the tree terpene alpha-pinene to the corresponding enantiomers of trans-verbenol at about equal rates. (-)-trans-Verbenol inhibited the response of females, but not of males, to a mixture of attractive pheromone components. Since the female initiates the attack on a pine tree, (-)-trans-verbenol may pla...

The use o f tools to obtain food is probably a long-standing hominid adaptation. Therefore, the rapid increase in hominid brain size over the last million years cannot be explained by selection for basic tool use alone. 350o alternative theories, here termed the ecological adaptation hypothesis and the intraspecific competition hypothesis, are reviewed and rejected. Instead, a combination of th...

In this paper, a predator-prey relationship in the presence of prey refuge was studied. The analysis dependence locally stable equilibrium points on parameters problem carried out. Bifurcation and limit cycles for model were analyzed to show dynamical behaviour system. results showed that system is at constant m = 0.3 harvesting rate H 0.3. However, increasing decreasing or vice versa, remains ...

Intraspecific competition for food is expected to increase the trophic niche width of consumers, defined here as their diet diversity, but this process has been little studied in herbivores. Population densities of small rodents fluctuate greatly, providing a good study model to evaluate effects of competition on trophic niche. We studied resource use in five arctic small rodent populations of ...

Mechanisms that regulate parasite populations may influence the evolution of hosts and parasites, as well as the stability of host-parasite dynamics but are still poorly understood. A manipulation experiment on the grooming ability of rodent hosts (Meriones crassus) and flea (Xenopsylla conformis) densities on these hosts successfully disentangled two possible regulating mechanisms: (i) behavio...

■ Abstract Seed-harvester ants are a dominant and conspicuous insect group throughout arid portions of the southwestern United States and northern Mexico, and they include ∼75 species. Intense study in the late 1970s and early 1980s led to the paradigm that interspecific competition for limited seed resources is the primary factor that structures seed-harvester ant communities. This review atte...