Zoologger is our weekly column highlighting extraordinary animals – and occasionally other organisms – from around the world

You’re mine now (Image: Sean McCann) Mind those antennae (Image: Kelly Ablard, Paul Schaefer, Gerhard Gries/Behavioural Processes/with permission from Elsevier)

Species: Ooencyrtus kuvanae (sometimes incorrectly spelled “kuwanai“)

Habitat: a native of Japan, although it has been introduced to most of the northern continents as a form of pest control


Falling in love for the first time is often disappointing. Your beloved proves immune to your charms, or even unaware that you exist, and they often rub salt into the wound by running off with some awful person that doesn’t care about them the way you do.

Male Ooencyrtus kuvanae wasps have no such problem. If they see a female they like, they call dibs on her with a flick of their antennae. Once she has been claimed by a male, the female resists all others, keeping herself just for him.

It’s easy to see how this system would benefit males, who can assemble a harem of females. What the females get out of the arrangement is still mysterious.

Mating frenzy

O. kuvanae is a parasitoid. The females lay their eggs in the eggs of another insect, the gypsy moth (Lymantria dispar), killing many of their host’s eggs. This has made O. kuvanae very popular: the gypsy moth is a major pest of oak forests, so O. kuvanae has often been introduced as a way to keep it under control.

The moths lay eggs in clumps, and many eggs in each clump get parasitised by the wasps. The short-lived wasps all hatch more-or-less simultaneously, so hundreds of males and females find themselves crammed together, creating an immediate race to find a mate.

Females produce one set of eggs in their lifetime and so only need to mate once, but males can best pass on their genes by mating with as many females as possible, so the rivalry between males is intense.

Wondering how the males went about getting multiple mates in such a competitive environment, Gerhard Gries of Simon Fraser University in Burnaby, British Columbia, Canada, and colleagues monitored captive insects as they courted each other.

Change of tactics

When a lone male was introduced to a group of females, he swiftly mated with all of the unmated, “virgin” females. But if there was more than one male, some of the males changed tactics. They began by quickly mating with one female, but after that they started “reserving” other females for later.

Gries’s team noticed that when a male decided to claim a female for his harem, he would approach from her left. Once in range, he tapped one of her antennae with one of his. Gries thinks this transfers an as yet unidentified pheromone onto the female’s antenna.

This pheromone effectively marks the female as “out of bounds”, he suggests. Males mostly avoided contact with tagged females and if a male did approach a tagged female, she evaded him.

From the males’ point of view, this strategy seems to pay off: males who tagged females secured more matings in the long run than males who simply mated with females as soon as they found them.

Fittest first?

But what do females get out of being tagged in this way? Although they are just as willing to mate with males who court immediately as with those who tag first – suggesting they aren’t picky – there could still be a way in which the females are indirectly choosing their males.

A male who swiftly finds and tags a female is probably in good physical condition, and may well have good genes. So if a female is tagged, she might secure good genes for her offspring by keeping herself for that male and resisting later propositions.

In effect, the females might have a policy of “first come, first served” – on the assumption that the first males to arrive are probably the best.

Journal reference: Behavioural Processes, doi.org/j5j