15.02.2019 change 15.02.2019

Dance, song and a show of force: love in the world of insects

Photo: Fotolia Photo: Fotolia

The mating season in the animal world is a time of intense efforts to win a partner in order to successfully breed. The richness of mating behaviours is greatest among insects, which results from their extraordinary diversity.

In the world of insects there is no shortage of mating dances and fierce fights, spraying pheromones and giving female gifts, says Dr. Radomir Jaskuła from the Department of Invertebrate Zoology and Hydrobiology, University of Lodz.

During courtship, insects often use specific "perfumes", or sex pheromones, which can be secreted by both sexes or just one of them. For the males of some nocturnal butterflies from the Sphingidae family, individual pheromone molecules sprayed in the air are sufficient to find the female even from a distance of several kilometres.

After locating the female, males of numerous species of insects, including damselflies (Calopteryx), two species of which can be found on the Polish rivers, try to impress the female by performing spectacular dances in flight.

"They flap their blue wings in a characteristic way. They hang in the air, or accelerate over short distances, trying to catch the attention of the female at all costs. During this dance, other males are brutally chased away. This +romantic+ dance can quickly end: if the female does not show interest in the admirer for too long, the male often moves to showing off its strength" - says Dr. Jaskuła.

A show of strength in relation to rivals is typical for many species of insects, especially beetles. Numerous species of stag beetles (Lucanidae) or rhinoceros beetles (Dynastinae), whose males have powerful mandibles or horns on their heads, use these "weapons" to fight competitors. Female calmly watches their duels, and the prize for the winner, who is usually the largest and strongest male, is mating with her.

During the mating season, males of many species of insects use sounds to attract females. Crickets and grasshoppers give solo concerts, but for example in the case of cicadas, thousands of males try to "outshout" each other, just so that they are chosen by a female, the biologist describes.

In many cases, male insects try to "win their partners` hearts" with various gifts. These gifts are often delicacies, as in the case of many species of herbivorous Heteroptera. The males bring seeds to their "chosen ones".

"If the seed is of proper quality, the female eagerly mates with the male, often while eating the gift" - he adds. Mecopterans use similar strategy; in their case, the gift is sometimes obtained at the risk of life, because males can steal dead insects from spider webs for future female partners.

Some gifts are valuable not only for the female but also for future offspring. In the case of some species of fire-coloured beetles (Pyrochroidae), during mating, in addition to their own genes, males also transfer chemical compounds that secure future eggs against potential predator attacks. Females are able to assess the attractiveness of a partner based on these compounds. The more deterrent substances the male is able to transfer, the more desirable he is.

Males of many species of insects also show "tenderness" to their partners, but only to stimulate them during copulation. Some beetles, grasshoppers or crickets stroke the female with antennae or palps to maximally prolong the sexual act. "The purpose of this behaviour is to pass as much of their own genetic material as possible, and thus increase the chance for more numerous offspring" - says Dr. Radomir Jaskuła from the University of Lodz.

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