The forest tent caterpillar moth (Malacosoma disstria) is a moth found throughout North America, especially in the eastern regions. Unlike related tent caterpillar species, the larvae of forest tent caterpillars do not make tents, but rather, weave a silky sheet where they lie together during molting. They also lay down strands of silk as they move over branches and travel as groups along these pheromone-containing silk trails. The caterpillars are social, traveling together to feed and massing as a group at rest. Group behavior diminishes as the caterpillars increase in size, so that by the fifth instar (molt) the caterpillars are feeding and resting independently.
The adult moths of this species favor oak, sweetgum, tupelo, aspen, and sugar maple for egg laying in the summer. The females lay eggs in masses of up to 300, which are stuck to twigs and covered with a gluey cement called spumaline, which prevents them from desiccating and freezing. Eggs hatch the following spring. The larvae can be found feeding on many other species of deciduous trees or shrubs. High population density outbreaks tend to recur at reasonably regular intervals every decade or so and usually last two to three years, during which time trees and shrubs can be almost completely denuded of leaves. Most plants replace the lost leaves without permanent damage.
Te
TerrestrialTerrestrial animals are animals that live predominantly or entirely on land (e.g., cats, ants, snails), as compared with aquatic animals, which liv...
Ov
OviparousOviparous animals are female animals that lay their eggs, with little or no other embryonic development within the mother. This is the reproductive...
F
starts withMature (pre-pupating) larvae are 2 to 2.5 inches (50 to 64 mm) in length. The caterpillars are black, dark brown, or gray, with broad blue longitudinal stripes and thin yellow stripes extending along each side. The back of each abdominal segment bears a white spot that is wider toward the head end. The sides are partially 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 (30 mm). Coloration is similar for males and females. The female's body is larger than the male's.
The insect is native to North America.
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 kilometers with the assistance of an unusually strong wind.
Eating times are variable. Foraging trips can occur at any time and are very coordinated: either the entire colony forages or no one does. A small proportion of starved individuals is enough to reach agreement and start group movement. However, this organized behavior and the high fidelity of caterpillars to pheromone hormone trails imply conservative foraging, which may trap caterpillars to poor food sources even if a better one is close by. Some plasticity in this behavior has been reported, which is modulated by the presence of caterpillars that are behaviorally more exploratory or that simply become more adventurous because they are starved, increasing foraging flexibility. With age, competition for food becomes more important, especially as resources become scarce. Grouping decreases growth rate via a decrease in food intake so ontogenetic changes toward more mobility and independence can be viewed as simple "scaling" relationships between caterpillars and food sources evolved to increase the benefits of individual foraging in later stages.
The first adults to eclose (emerge from their pupa) in early spring are the males. Starting at around 5:30 p.m., hundreds of males fly vigorously and relentlessly in search for cocoons containing females about to eclose. They approach trees and move around them, zigzagging and crawling on branches. If they do not find females with whom they will have the chance to copulate, they fly off and continue their search. It has been suggested that male activity is dependent on temperature, since below 59 ˚F (15 ˚C) only a small number of males are found to be actively looking for females. It has also been reported that females emit a calling pheromone before they emerge from the pupae, causing an increase in male activity around the cocoon before they eclose. In addition, males have been seen approaching and moving around brown objects, suggesting that males also use visual cues to find females. Within one or two seconds after the tip of the female abdomen clears the cocoon, males begin copulation, which lasts an average of 202 minutes. In order to position himself, the male moves backwards and bends his abdomen towards the female, pushing the tip towards the female's bursa copulatrix. There is a significant positive correlation between the body sizes of copulating pairs, which indicates that mating is not random with respect to size, presumably because of male-male competition for larger females.Independently of whether they are or not copulating, females do not move more than a few centimeters from their eclosion site until they are able to fly away, usually at twilight. Females start preparing for flight by fanning their wings. Frequently, fanning begins during mating and is often the first sign of its end as females fly away soon after.
