Michelle Dickinson: nanotechnologist on the new research into cockroach relationships

Cockroaches are not usually associated with romance.  But scientists publishing in the journal Royal Society Open Science have just discovered something surprising - some cockroach couples appear to form exclusive, long-term partnerships. And the way they start that relationship is by eating each other’s wings.  Researchers already knew that during courtship, Salganea taiwanensis cockroaches sometimes chew off and eat their partner’s wings. What they didn’t know was whether this strange behaviour had a deeper social purpose.  To find out, scientists designed an experiment to test whether the wing-eating ritual might actually help form a pair bond between the insects.  In the study, researchers observed two types of cockroach pairs:  Couples that had already eaten each other’s wings  Couples that had not yet performed the ritual  Each pair was placed inside a small nest environment, similar to the wooden spaces they inhabit in nature.  Then researchers introduced an unfamiliar cockroach into the nest and observed how the pairs reacted.  Cockroach couples that had already completed the wing-eating ritual became highly aggressive toward intruders.  They rammed into the stranger repeatedly to drive it out of their nest. Across hundreds of recorded attacks, almost none were directed at their partner.  By contrast, cockroach pairs that had not yet eaten each other’s wings behaved very differently. They were far more passive and rarely defended the nest aggressively.  This suggests the wing-eating ritual may act as a kind of biological commitment ceremony, triggering the formation of an exclusive partnership.  Pair bonding, forming a long-term relationship with one partner is something scientists often associate with vertebrates like humans, birds, and some mammals.  Seeing this kind of selective partnership behaviour in an insect is unusual.  The researchers say their work provides the first experimental evidence that insects can form exclusive partnerships using behaviours similar to those seen in animals with much more complex brains.  Cockroaches are biparental, meaning both the male and female care for their young.  Because their offspring develop slowly, having two committed parents dramatically improves the chances that the young will survive.  From an evolutionary perspective, forming a stable partnership makes sense.  Studies like this remind us that even insects can have surprisingly complex social behaviours.  LISTEN ABOVESee omnystudio.com/listener for privacy information.