This undated handout photo provided by the journal Science shows Bicyclus anynana butterflies mating. – AP Photo

WASHINGTON: When certain caterpillars are raised in warm, moist conditions they grow into butterflies that exhibit what some would consider traditional roles – males pursuing females.

But new research has found that when they are raised in dry, cool conditions, it is the females that become aggressive adults, actively courting the males.

Researchers led by Kathleen L. Prudic of Yale University report their findings in Friday’s edition of the journal Science.

They studied Bicyclus anynana, known as the squinting bush brown butterfly because of the eye-like patterns on their wings.

While not visible to humans, pattern reflections make the ones doing the courting appear brighter in the eyes of those being courted, Prudic explained in a telephone interview.

“It makes them more noticeable,” she said, “kind of like a nice car.”

Insects have a short amount of time to mate and lay eggs, she said, so they “hit the ground running.”

When these butterflies mate, males deliver nutrients to the females in addition to sperm. Since cool, dry weather provides fewer resources for butterflies, these extra nutrients can be important to the females, who display to as many males as possible to obtain the extra resources.

The ladies with the brightest spots tend to have the most success.