Mysterious monogamy in Madagascar

A number of recently described bush-cricket species could prove to be surprising in a variety of ways.

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Oncodopus janetae

This species may by monogamous © George Beccaloni

 

Two scientists have described several new species of bush-crickets in Madagascar, many of which exhibit unusual behaviours.

Observations of these insects suggest that they could be monogamous, a behaviour which is extremely rare in insects.

George Beccaloni, co-author of the paper, witnessed male and female Oncodopus janetae resting together in a sheltered cavity, described as a harbourage.

“I have a theory as to why these bush-crickets have evolved their odd, possibly monogamous, behaviour,” says Beccaloni.

“Because of the harsh, hot conditions during the day in the dry forests in which they live, they evolved to shelter in harbourages during the day (unlike most other bush-crickets). This led to the reduction of their wings (which might get damaged in tight holes) and the evolution of their mate-guarding behaviour, as harbourages are scarce.”

In order to ensure that the male mates with the female, he may need to guard her against other males.

A number of other factors have not yet been researched, such as whether a male guards the female when they are outside of the harbourage.

O.janetae was named by the scientists after Beccaloni’s wife.

Another interesting observation noted by the scientists was the enlarged forelegs of the Colossopus grandidieri species, which displays unusual behaviour when threatened. It attempts to grab the ‘attacker’ with these forelegs.

 

Watch a video of the 'aggressive' bush-cricket

 

“As far as we are aware, no other bush-crickets have such enlarged forelegs,” explains Beccaloni.

“Some other species try to grab and bite and attacker – but I have not seen any acting in quite so active and ‘aggressive’ a manner as C. grandidieri.”

In total, Beccaloni and his co-author Mustafa Unal described seven species of bush-crickets for the first time, using both museum specimens and recently collected insects, despite the fact they are among the largest insects in the country.

They are also “some of the largest bush-crickets in the world – yet they have remained unnamed until now,” says Beccaloni. “This shows how poorly known Madagascar’s insect fauna is.”

All the newly described species are found in the dry forests of the island, many of which are threatened by human activities such as charcoal production.

 

Read the full paper.

 

Read more wildlife news stories in BBC Wildlife Magazine

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