Male wasps use spiky genitals to defend themselves from predators

Male mason wasps don’t have any sting, however they’ve spines on their genitals that may trigger a pricking ache, and these are efficient at deterring some frogs from consuming them

By Matthew Sparkes

Feminine wasps have a venomous sting to discourage predators, however males lack this safety. Now, researchers have found that male mason wasps have an alternate defence technique: utilizing their spiky genitals to assault animals that attempt to eat them.

Male wasp genitals embody an aedeagus, the insect model of a penis, and a pair of parameral spines. In another insect species, comparable organs injure females throughout mating to stop her from mating once more. However mason wasps (Anterhynchium gibbifrons) noticed mating in a laboratory don’t appear to make use of these spines in opposition to their mates.

Shinji Sugiura at Kobe College, Japan, says his group determined to discover whether or not the spikes had been as an alternative used for defence after his colleague Misaki Tsujii was “stung” by a male mason wasp, though the males don’t have any precise sting.

“The male wasp used a pair of sharp spines in the genitalia to pierce her finger,” says Sugiura. “Surprisingly, the male ‘sting’ caused a pricking pain. I hypothesised that the male genitalia of A. gibbifrons function as an anti-predator defence.”

The group positioned single male wasps in a container with both a tree frog (Dryophytes japonicus) or a pond frog (Pelophylax nigromaculatus). Every time, the frog attacked the wasp. However whereas all the pond frogs efficiently ate the wasp, the tree frogs rejected it 35 per cent of the time.

The wasps had been regularly noticed to pierce the mouth or face of frogs with their genitalia whereas being attacked. In one other take a look at, tree frogs had been put in a container with male wasps that had been castrated with forceps, and so they all ate the wasps.

“Because wasps and bees evolved venomous stings from ovipositors [the tube used to lay eggs], their males, which lack ovipositors, were believed harmless. However, we found that male wasps use the genital spines to counterattack predators,” says Sugiura.

When feminine wasps had been examined as an alternative, all the pond frogs ate them, however 87.5 per cent of the tree frogs rejected them, exhibiting that their stings are simpler than the male genital defences.

The “sting” of male wasps had been documented earlier than, scoring a degree of 1 on the Schmidt sting ache index, in contrast with 1.5 for feminine stings. However this analysis was the primary to make use of actual predators to check the spines’ goal.

Journal reference: Present Biology, DOI: 10.1016/j.cub.2022.11.030

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