Most Indians will swear that their mothers are the best cooks in the world. This, however, doesn’t mean that the fathers can’t cook. Many men are quite adept at cooking, but try explaining that to the children.

nfortunately, many mothers share this prejudice and think that they know best on what to feed and how to feed their children. There are parallels in insect communities too. Take the case of paper wasps (Ropalidia marginata). Female paper wasps have serious doubts about the ability of their male counterparts to feed larvae.
Now a new study by two Bangalore-based researchers has discredited this notion somewhat. It appears that males don’t feed larvae under natural circumstances because the females don’t give them the opportunity to do so, explains Professor Raghavendra Gadagkar at the Centre for Ecological Sciences, Indian Institute of Science (IISc), Bangalore. The study was published in the journal Animal Behavior early this year.

Gadagkar, the lead author of the study, says an intriguing aspect of societies of hymenoptera (an insect order to which ants, wasps and bees belong) is that they are “feminine monarchies”. In other words, these societies have queens but no kings and all the workers are females. “Males do little more than transferring their sperm to virgin queens while all the work involved in nest building, brood care and finding and processing food is done by the females.”

Trying to unravel the secret of this ‘chauvinist behaviour’, Gadagkar and his student, Ruchira Sen, decided to study the feeding of larvae (an important social task) in different colonies of paper wasps. The researchers concentrated on the paper wasp because, unlike some other social wasps, males of this particular specie were never seen to feed larvae.

Gadagkar explains that they started with three working hypotheses on why male paper wasps did not participate in this social task. The first one states that the males are simply incapable of feeding larvae. According to the second one, the males don’t get enough to eat because they are can’t forage for food on their own. Therefore, they have very little food to offer to larvae. The third hypothesis, however, says that females are much more efficient at feeding larvae and they are averse to delegating this task to the “inefficient males”.

To test these premises, the IISc researchers studied different types of nests of paper wasps, which are found in all parts of India except in the northeastern states. Sen, co-author of the study, says they observed nests with both male and female wasps with no food supplement, and male-female nests “to which we offered excess food”. They also observed all-male nests (created by removing all the females) in which the males were hand fed to satiation.

“Hand feeding the males was necessary because males cannot forage and find food in the absence of females. Excess food was given to these males so that they might feed larvae if they could,” explains Sen, who is pursuing her PhD in animal behaviour at IISc. But hand feeding the larvae was not a very easy task. “The males didn’t take the food from me very readily. I had to make very small pieces of the food and hold it in front of their mouths using a thin stick and wait patiently for them to take it,” she says.

Her hours of ‘baby sitting’ finally paid off when the males isolated from the females were seen to feed larvae with the excess food. And this feeding was comparable to the rate of females feeding larvae. In the case of nests that had both sexes but without food supplement, it was observed that males didn’t indulge in feeding. However, in both-sex nests, but with food supplements, very few males fed larvae.

Another significant observation was the different feeding techniques employed by males and females. While males fed larvae with only solid food after chewing it (mastication), females fed larvae both after mastication and regurgitation (feeding the juice from the swallowed food). It was also observed that the males only fed some of the larger larvae and ignored the smaller ones. “This is perhaps because it’s easier to feed the bigger larvae as they can easily accept solid food. But the smaller ones with very small mouth parts are unable to do so,” surmises Sen. As a result, a substantial proportion of large larvae and almost all the smaller larvae in an all-male nest died from starvation.

Interpreting these observations, the researchers conclude that male paper wasps are not incapable of feeding larvae, but they don’t do so in natural colonies because “they don’t have access to enough food and/or because females leave no opportunity for them to do so”. In other words, the female wasps are rightly prejudiced against “male efficiency”.

Mother Nature, too, has done a great injustice to these fathers. Contrary to the dictates of natural selection, the male wasps have puzzlingly not evolved into more efficient workers. Gadagkar proudly admits that their present research has thrown up this evolutionary puzzle. Like other true men of science, he asserts, “Answering one question raises at least one more — and that’s how it should be.”