Helen said she cut the tent caterpillars out of the trees in her yard today. I asked if she burned them and she said yes because I told her to. If you don't burn them, they will live on and produce many more worms next year. I was trying to tell her that the worm was just one stage of their life cycle, and I thought the adult stage was a moth of some sort, but was not sure. Now I know.
This is what the adult looks like.
The following description of the tent caterpillar life cycle is based on that of the eastern
tent caterpillar, the best known species. The details of the life histories of
other species vary to a small extent.
Tent caterpillars hatch from their eggs in the early spring at
the time the leaves of their host trees are just unfolding. The caterpillars
establish their tent soon after they eclose.
The tent is constructed at a site that intercepts the early morning sun. The
position of the tent is critical because the caterpillars must bask in the sun
to elevate their temperatures above the cool ambient temperatures that occur in
the early spring. Studies have shown that when the body temperature of a
caterpillar is less than about 15 °C, digestion cannot occur. The tent
consists of discrete layers of silk separated by gaps and the temperature in
these compartments varies markedly. Caterpillars can adjust their body
temperatures by moving from one compartment to another. On cool mornings they
typically rest in a tight aggregate just under a sunlit surface of the tent. It
is not uncommon to find that the temperature of the aggregate is as much as 30 °C
(54 °F) warmer than the surrounding air temperature on cold but sunny
spring mornings. Later on in the spring, temperatures may become excessive at
midday and the caterpillars may retreat to the shaded outside surface of the
tent to cool down.
The digestive physiology
of tent caterpillars is tuned to young leaves, and their need to complete their
larval development before the leaves of the host trees become too aged for them
to eat compels them to feed several times each day. At the onset of a bout of
foraging, caterpillars leave the tent en masse, moving to distant feeding
sites. Immediately after feeding the caterpillars return to the tent and
aggregate in sunlight to facilitate the digestive process. Thus, eastern tent
caterpillars are central place foragers. In contrast, the forest tent
caterpillar is a nomadic forager that establishes a series of temporary resting
sites during the course of its larval development.
Studies have shown that eastern tent caterpillars recruit their
tent mates to go on food finds. Caterpillars move from the tent in search of
food, laying down an exploratory pheromone trail as they pass over the branches
of the host tree. These chemical exploratory trails allow caterpillars to find
their way back to the tent. If a caterpillar finds food and feeds to repletion,
it returns to the tent, laying down a recruitment trail that serves to recruit
hungry tent mates to its food find. The chemical nature of the pheromone has
been determined, but it is unclear how exploratory and recruitment trails
differ. The chemical recruitment trail of the eastern tent caterpillar is
remarkably similar to the pheromone trails that are used by ants and termites
to alert nest mates to the discovery of food.
Leaves consist largely of nondigestible components, and it has
been estimated that tent caterpillars void as fecal pellets nearly half of the
energy they ingest. Consequently, a colony of caterpillars produces large
quantities of fecal pellets. This is particularly noticeable during outbreaks
of the forest tent caterpillar. Fecal pellets dropping from treetops in which
the caterpillars are feeding create the auditory illusion of rainfall. Tent
caterpillars typically have five to six larval instars. It is
estimated that the last instar consumes about 80% of all the food taken in by a
larva during the whole of its life cycle. Consequently, it is not uncommon for
populations of forest tent caterpillars to go unnoticed until the last instar,
when their feeding causes extensive defoliation of trees.
Caterpillars grow rapidly and typically complete their larval
development in seven to eight weeks. When fully grown, the caterpillars leave
the natal tree and seek protected places on the ground or under the eaves of
buildings to spin their cocoons. About two weeks later, they emerge as adults.
Shortly after eclosing from the cocoon, the female moth secretes a pheromone which
draws males to her. Mating typically occurs in the early evening and the mated
female, already fully laden with eggs, typically oviposits the full complement
later that same evening. The eggs are placed around the circumference of a
branch and covered with a frothy material called spumaline. Spumaline is hydrophilic and
prevents the eggs from drying out. It also serves as a protective covering
which limits the ability of small wasps to parasitize the eggs. Although the
male moth may live for a week or more, the female dies soon after laying her
eggs. Thus, the whole of the female's adult life may take place in fewer than
24 hours.
Shortly after the egg mass is deposited, embryogenesis begins.
Within three weeks or so, small larvae can be found within each egg mass. These pharate larvae
lie sequestered within the shells of the eggs until the following spring. Thus,
these encased larvae are the most durable of the insect's life stages. In
northern areas, the pharate larvae are highly freeze-tolerant and can withstand
midwinter temperatures of −40 °C or lower.
