Forest tent caterpillar moth

Appearance

Forest tent caterpillars are usually just over 2 inches in length, but some have been reported to reach 5 inches. They are black, dark brown, or gray, with blue and faint yellow longitudinal stripes. Each abdominal segment bears a white spot, which are covered with fur-like long setae. The adult moth that emerges after pupation is yellow or tan with a thick, short, furry body. The wingspan is about 1.5 inches.

Distribution

Forest tent caterpillar populations increase periodically to outbreak densities. Not much is known about the factors that lead to the initiation of forest tent caterpillar outbreaks, although some plausible mechanisms are higher temperatures in the spring, phenological synchrony with their host-plants, and reduced predation enemies. Whatever the cause, outbreak densities give rise to cyclic population dynamics, characterized by highest fecundity at peak population density and reduced fecundity for several generations during decline.
At low population densities, moths are found mating high above the ground, in the forest canopy. Mating starts late in the day and copulations are short. In contrast, during high-density outbreaks, mating takes place on lower vegetation, presumably because caterpillars descend to forage in less defoliated areas, where they form their pupae. This high population density increases the operational sex ratio and significantly intensifies male-male competition. As a result, copulations begin earlier in the day and last longer in an attempt to minimize sperm competition. In addition, such high densities enhance female opportunities for being selective regarding males.

During high outbreak densities, some males, called “hangers,” change their copulation behavior. They do not attach physically to the branch while mating, which allows them to mate longer and counteract their mate’s efforts to reject them. This behavior increases the percentage of eggs they fertilize as they delay their mated female from remating and reduce number of potential mates the female can have. This hanging behavior does not appear at low population densities, presumably because it is more energetically costly and more conspicuous, since it can attract more males that can potentially interfere in the copulation process. As a result, males only exhibit this behavior when they are trying to prolong mating to reduce sperm competition.

Behavior

The forest tent caterpillar moth is nocturnal, taking flight soon after nightfall and returning to rest before dawn. It is not known how far an egg-laden female can fly, but there is one credible report of this species flying hundreds of kilometres with the assistance of an unusually strong wind.Their behavior is neutral. They are a species that are quite calm. They will not bite if handled.Forest tent caterpillar populations increase periodically to outbreak densities. Not much is known about the factors that lead to the initiation of forest tent caterpillar outbreaks, although some plausible mechanisms are higher temperatures in the spring, phenological synchrony with their host-plants, and reduced predation enemies. Whatever the cause, outbreak densities give rise to cyclic population dynamics, characterized by highest fecundity at peak population density and reduced fecundity for several generations during decline.
At low population densities, moths are found mating high above the ground, in the forest canopy. Mating starts late in the day and copulations are short. In contrast, during high-density outbreaks, mating takes place on lower vegetation, presumably because caterpillars descend to forage in less defoliated areas, where they form their pupae. This high population density increases the operational sex ratio and significantly intensifies male-male competition. As a result, copulations begin earlier in the day and last longer in an attempt to minimize sperm competition. In addition, such high densities enhance female opportunities for being selective regarding males.

During high outbreak densities, some males, called “hangers,” change their copulation behavior. They do not attach physically to the branch while mating, which allows them to mate longer and counteract their mate’s efforts to reject them. This behavior increases the percentage of eggs they fertilize as they delay their mated female from remating and reduce number of potential mates the female can have. This hanging behavior does not appear at low population densities, presumably because it is more energetically costly and more conspicuous, since it can attract more males that can potentially interfere in the copulation process. As a result, males only exhibit this behavior when they are trying to prolong mating to reduce sperm competition.

Reproduction

The social caterpillars of "Malacosoma disstria" are nomadic and forage as a group. The fifty to two hundred larvae that result from a single egg-mass live together for most of their larval stages. Trails of silk heavily loaded with pheromones secreted by other colony members induce larvae to move, while the close presence of other colony members brings them to quiescence. This indicates that there are social cues that are used to increase the locomotive efficiency of each individual larva. Pupation occurs after caterpillars reach a size threshold that is attained more quickly when caterpillars forage in groups. This is particularly important since delayed development to threshold increases the risks of predation and food depletion. However, as larvae proceed into the later instars, they become increasingly independent and by the fifth instar rarely form aggregations. This ontogenetic change in gregariousness results from an increase in the costs of maintaining grouping due to changes related to predation, thermoregulation, silk production, and foraging.