Parasitic wasps are best known for leaving mummified insect victims in their wake as they lay eggs on or in hosts' bodies. Now studies into their sex lives reveal a softer side

Like something from a science fiction film, parasitic wasps are best known for leaving mummified insect victims in their wake as they use hosts’ bodies to deposit their larvae.

The parasitoids exploit a range of victims including aphids, weevils and butterfly larvae, and can lay their eggs on or in the victim’s body, explains researcher Giovanni Benelli from the Department of Agriculture, Food and Environment at the University of Pisa in Italy.

“The eggs hatch and the young instar of the parasitic wasp develop [by] feeding on the victim’s tissues.”

One parasitic wasp can even turn its ladybird host into a 'bodyguard', making it twitch and grasp, warning off predators, while the parasite breaks out of its body.

Now Dr Benelli and other researchers are on a mission to uncover the secret mating habits of the macabre minibeasts.

Here are four things you almost certainly didn’t know about parasitic wasps' love lives.

1. High-frequency wing fanning is sexiest for female wasp

Lysiphlebus testaceipes is a tiny wasp that attacks more than 100 aphid species and leaves its babies inside hosts' bodies. The parasitoid starts life when it emerges from its gruesome protective case.

Little is known about the species’ mating system.

But a new study by Dr Benelli and colleagues shows when it comes to courtship in wild Lysiphlebus testaceipes, a high-frequency wing fanning display is especially attractive to females.

High-speed video recordings revealed males that produced high-frequency fanning signals had greater mating success than those with low-frequency fanning displays.

When approaching a potential mate, males fan their wings after receiving a waft of a sex pheromone given off by the female. They then tap their antennae on the female’s body and attempt to mount her. If successful, the female keeps still while the male makes genital contact and periodically taps her head.

From the females' perspective, fanning frequency could be an indicator of the males' quality as a mate.

2. Male parasitoids sing to their lovers

It’s an unusual and not a particularly melodic song, but Psyttalia concolor – a parisatoid of fruit flies – use song to secure a lover.

By fanning their wings, they produce a series of sound pulses.

One study found males were more likely to mate successfully with a female when these pulse durations were longer.

Listen below to the unusual acoustic signals of male Psyttalia concolor during a courtship display.

3. Wasps are more amorous in the mornings

Male Psyttalia concolor are apparently more amorous in the mornings.

Another study carried out by Dr Benelli showed males were more likely to be successful in mating at 9am than at 6pm.

The team recorded that the number of wing-fanning displays and mating attempts were higher in the morning than in the afternoon.

And sex was longer in duration early in the day.

The scientists wanted to find out more about the parasitic wasp's mating habits in order to inform projects to mass-rear the insect for use in biological control of agricultural pests.

4. Older male wasps mix up younger males and females

Older male parasitic wasps try to court both young males and females.

This could be due to a sex pheromone given off by both females and males during the first 32 hours of their lives, which makes the sexes indistinguishable to older males, a study on the species Lariphagus distinguendus showed.

Older males were found to fan their wings during the mating ritual in the same way towards both sexes.

After 32 hours, young males deactivate the chemical cues and the older males no longer try to court them.

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