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Male Insects Rule in a Tropical Society.

Who says that males can't amount to much, that they're Nature's weaklings, destined to be bullied and bitten, fed only scraps, and quickly chased out of their mother's home by their sisters?

Now, Sean O'Donnell of the University of Washington in Seattle provides what he says is the first report of a social insect species in which guys rule. Males of the Costa Rican wasp Mischocyttarus mastigophorus pounce on the queen in their nest and attack female workers, who curl into a submissive crouch or flee, reports O'Donnell. He describes this behavior in an upcoming Ethology.

"Male social insects have gotten short shrift" by researchers, laments O'Donnell. "The prevailing idea has been that they're not very interesting."

Among most of the wasp species studied so far, the males' lives are nasty, beleaguered, and short. Philip T. Starks of Cornell University has even described "male stuffing" among paper wasps in the United States. When a worker brings food to the nest, other females jam their brothers headfirst into empty nest cells. "This behavior precludes the rather lazy males from consuming food" needed by the larvae, Starks says.

There's none of this indignity among M. mastigophorus. O'Donnell and his colleagues perched on scaffolding or ladders for hours to watch 6 nests and counted males at 32 others.

"It was strikingly obvious that males were dominating," O'Donnell says. They grabbed more food from returning foragers than workers did. Males even snatched food from their mom, the queen.

The females didn't give up the food because the males are such handy guys to have around, O'Donnell notes. He acknowledges that males of this species "actually did a little bit of work." They helped fan an overheated nest, bailed out a flood, and sometimes chewed food for the larvae. However, he says, "your anthropomorphic reaction is that they're not really very good at it."

O'Donnell proposes that male power relates to climate. Wasp colonies in temperate zones synchronize reproduction with the seasons and can wait until the end of the summer to raise males. Starting earlier just drains resources.

O'Donnell's wasps, however, live in a cloud forest where colonies do not synchronize mating times. The males, he finds, remain in their home colony for an unusually long period. They can father a new colony--and thus prove useful--just about any time. As people check for male dominance in other tropical species, "I believe we'll find more," O'Donnell predicts.

Starks raises the possibility that it's not just males who take advantage of workers, but all future players in reproduction, including females who will grow into queens. O'Donnell did see sisters tussle but couldn't tell the princesses from the proletariat. "Without that information, it cannot be conclusively shown that males, as opposed to all reproductives, are treated especially well," Starks says.

Male dominance in the tropics sounds like a reasonable idea to Robert Jeanne of the University of Wisconsin-Madison. He has seen rough males in another tropical wasp species. Mary Jane West-Eberhard of the Smithsonian Tropical Research Institute, who is currently working in San Jose Costa Rica, also has described a tropical male paper wasp that holds its own with its sisters.

O'Donnell's report "is the first in the sense he's recognized it as dominance," Jeanne says. "The rest of us said, `Wow, the males are aggressive.'"
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Title Annotation:the normal female rule in insect societies is apparently reversed, with males ruling, in the society of the Costa Rican wasp
Author:Milius, S.
Publication:Science News
Article Type:Brief Article
Date:Feb 20, 1999
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