If you've spent any time watching insects, you've probably stumbled on a pair of lady beetles or flies joined together in the throes of love. When you're a lone bug in a big world, finding a partner of the same species and the opposite sex is not always that simple. So how do insects find a mate?

Love at First Sight—Visual Signals

Some insects begin their search for a sexual partner by looking for or giving visual cues or signals. Butterflies, flies, odonates, and luminous beetles use visual signals most often.

In some butterfly species, males spend much of the afternoon patrolling for receptive females. Anything that looks like a female may be inspected, especially if the object is a desired color and "floats like a butterfly," to borrow a phrase from Muhammed Ali.

Many species of flies perch in a place that provides a clear view of the area. The fly sits, watching for any flying object that might be a female. If one appears, he quickly takes flight and makes contact. If his quarry is indeed a female of his own species, he escorts her to an appropriate place for mating—perhaps a leaf or a twig nearby.

Fireflies may be the most famous insects that flirt using visual signals. Here, the female sends the signal to lure a male. She flashes her light in a specific code that tells passing males her species, her sex, and that she is interested in mating. A male will reply with his own signal. Both male and female continue to flash their lights until they have found each other.

Serenades of Love—Auditory Signals

If you've heard the chirp of a cricket or the song of a cicada, you've listened to insects calling for a mate. Most insects that make sounds do so for the purpose of mating, and males tend to be the crooners in species that use auditory signals. Insects that sing for a partner include Orthopterans, Hemipterans, and Coleopterans.

The best-known singing insects must be the male periodical cicadas. Hundreds or even thousands of male cicadas congregate in an area after emerging and produce an ear-splitting chorus of song. The cicada chorus usually includes three different species, singing together. Remarkably, the females respond to the song and are able to find mates of the same species from within the chaotic choir.

Male crickets rub their forewings together to produce a raspy and loud song. Once he lures a female close to him, his song changes to a softer courtship call. Mole crickets, which are ground dwellers, actually construct special entrance tunnels shaped like megaphones, from which they amplify their calls.

Some insects simply tap on a hard surface to produce their love calls. The death-watch beetle, for example, bangs his noggin against the roof of his tunnel to attract a mate. These beetles feed on old wood, and the sound of his head tapping resonates through the wood.

Love Is in the Air—Chemical Cues

French naturalist Jean-Henri Fabre discovered the power of the insect sex pheromones quite by accident in the 1870s. Male peacock moths came flitting in the open windows of his laboratory, landing on the mesh cage of a female. He tried to fool the males by moving her cage to different locations, but the males always found their way back to her.

As you might suspect from their plumose antennae, male moths search for suitable female mates by sensing sex pheromones in the air. The female cecropia moth emits a scent so powerful it attracts males from miles around.

A male bumble bee uses pheromones to lure a female to a perch, where he can mate with her. The male flies along, marking plants with his perfume. Once he sets his "traps," he patrols his territory waiting for a female to land on one of his perches.

Unmated Japanese beetle females release a strong sex attractant, which quickly draws the attention of many males. Sometimes, so many male suitors appear at one time that they form a crowded cluster referred to as a "beetle ball."