Overview
Males and females find each other by sensing one another's pheromones. Within males' abdomen are sperm producing organs. When the male begins to mate with a female, he clasps her abdomen with his (claspers). He ejaculates his semen into a small storage pouch, the bursa, which is located inside the female's abdomen. They mate facing in opposite directions with their abdomen attached.
She lays 100-1000 eggs! When the butterfly is ready to deposit her eggs, she will place them on a very specific host-plant. Some species lay eggs in clusters; some lay them individually. The butterfly needs to make sure that at least some of her babies survive and since only a very small amount (2%) of all eggs hatched are expected to survive into adulthood, she needs to lay a lot of eggs. The most common causes of death of eggs include climactic conditions, viruses and predators.
Mate-Finding
Butterflies use two different flight patterns to obtain a mate: Perchant Behavior and Patrolling Behavior. With Perchant Behavior male butterflies go to certain areas and wait. Usually resting on some object the males will dart out at passing animals and objects to determine whether they are females of their own species. If the passer by isn't, they will return to their vantage point. Female butterflies will fly to these places to seek a mate. These areas are usually fixed within each species and both sexes are drawn to them.
With Patrolling Behavior males actively search for females by flying almost constantly. In some species patrolling males will track females scent to further aid them in their search. Usually though scents are only used in actual courtship.
Male's more commonly use movement and wing color to help them find females. Patrolling males are attracted to objects at rest whereas Perching males are attracted to moving or fluttering objects.
Butterflies' compound eyes see all colors ranging from red to violet including even ultraviolet light that humans can't see. Compound eyes are excellent at detecting quick motion but poor at detecting shape and pattern. This ability to detect quick motion but lack of shape determination causes many male butterflies looking for females to approach birds, wasps and even blowing leaves.
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Courtship and Mating
Once a male does find a female who is ready to mate, the female will land and they will mate quickly. This will occur often without any courtship ritual. Courtship may take place though as a characteristic flight such as a zigzag dance or both may hover along side each other. Unreceptive females may perform manuevers to discourage the pursuing male, these include: flapping her wings rapidly and flying upward followed by a rapid descent. These maneuvers are often refered to as rejection dances. Other rejection methods are: moving her abdomen up between her wings so that the male cannot join, releasing pheremones, and crawling or flying away.
The main purpose of courtship is to determine whether or not the other butterfly is a heathly member of the right species. Odor, color and pattern are all used to determine this. Unlike humans butterflies can see ultraviolet. Scientist have just begun to determine how ultraviolet light is used by butterflies and other insects.
Once a female has accepted a mate, mating can take from 15 minutes to 3 hours depending on the species. Most mating though takes approxiametly 30 - 40 minutes.
Egg Laying and Larval Nests
Once a female mates she may be able to lay eggs immediatly although most species wait 1 - 2 days after mating to begin egg laying. Some species in the lab will lay up to 1,000 eggs but usually in nature a female will lay less than a hundred.
Larvae see weakly, travel slowly and are usually picky eaters. Therefore females try to lay their eggs on their larvae's hostplant. To determine this females use their strong sense of scent to locate the plants. After locating the plant the female will double check her choice by drumming on the leaves or stems with the tips of her forelegs. These foreleg tips contain clumps of hairlike taste organs that help the female check for certain plant chemicals that will verify if her selection is correct. Once she has verified her selection each egg is glued to the surface of the plant to ensure they won't fall off.
Female butterflies usually lay only one egg at a time, than move onto a new plant to lay another egg. This avoids competition for food between larvae. Some species do lay their eggs in clusters and these young larvae will usually feed together and live inside a common silk nest.
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