Each species of moth lays a different number of eggs, and the range is vast: Some lay as few as 40 at a time, some up to 1,000. Most female moths don't live long after laying eggs, but the large number of offspring they create allow their species to carry on -- sometimes in overabundance, when conditions are right.
Finding a Mate
Because most moth species prefer to move around at night, they typically use pheromones instead of sight to find each other. In some species, such as the European gypsy moth, the female exists only to breed -- she doesn't even fly, just releases pheromones almost immediately after exiting her cocoon. Most females mate with only one male, while males can mate with several females during their short adult lives.
After mating with an adult male moth, females lay eggs quickly. The clothes moth lays about 40 eggs, often in and among the clothes in your drawers and closets. This allows the larvae to have an immediate meal of natural fibers when they hatch. Indian meal moths, which invade your pantry in search of food such as grains, cereals, herbs, dried fruit and pet food, lay more than 200 eggs. When the caterpillars hatch, they can chew through paper or cardboard containers to reach their meals. Gypsy moths, which typically live outside and feed on tree leaves, lay up to 1,000 eggs; with each caterpillar capable of eating 1 square foot of leaves by the time they're ready to make a cocoon, these moths can decimate their host trees.
First Time's a Charm
Most moths have short adult life spans. Some, such as the Indian meal moth, live for a week or less -- the adult moths don't eat and live only to reproduce. Others might live three to four weeks, long enough to find a mate; the females often die before the males, passing away shortly after laying eggs. Females get just the one chance to lay eggs. Even if the females live for a few days after producing eggs, they won't mate again.
Clothes moth larvae hatch from their eggs in just a few days, while moths such as the gypsy moth might spend months as eggs during the winter waiting on warm spring days to induce hatching. The larvae can live for several weeks or months -- sometimes up to two years, in the case of clothes moths -- before getting the urge to build cocoons. They typically pupate for two to four weeks before emerging as adult moths. Although moths tend to lay many eggs, the ones that produce the most, such as the gypsy moth, are subject to a variety of predators, including other insects, spiders, birds and mammals such as squirrels. These predators often eat the caterpillars, or larval stage, of the moths, which is a natural means of limiting population. In years when few predatory creatures exist, larger moth populations are seen.
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