Male fireflies that attract mates with flashes of light also have a seductive gift to draw eligible females: a "nuptial gift".

Unraveling the spermatophore package was done by researchers from Tufts University in collaboration with MIT giving a new peek into the sexual selection process. The researchers found females are showing more preference to males having the largest nourishing gift because it contains sperm and nutrients that enrich the female's productivity and health.

"We found that firefly nuptial gifts are complex, elegant structures manufactured by a bevy of male glands," said Nooria Al-Wathiqui, co-first author of the study.

The previously unknown molecular composition of the gift has now been revealed and the findings were published in Scientific Reports.

Rich In Proteins

In the nuptial gift of Eastern firefly, Photinus pyralis, researchers found at least 200 proteins. In terms of function, they were similar to other insects with structural proteins seen as the fabric of nuptial gift and enzymes working to unzip it.

Sara Lewis, author and professor of biology at Tufts University's School of Arts and Sciences, hailed new technologies for wider decoding of the gift bundles.

The metabolomic analysis also found Lucibufagin in the gift — a bitter toxin that protects firefly eggs. It is believed that females use the toxins to defend themselves and protect offsprings against attackers.

Declining Firefly Populations

Meanwhile, concerns are up over declining populations of fireflies. The International Firefly Symposium had presented evidence of depleting numbers and called for "an urgent need for conservation of their habitats."

Many scientific papers have documented regional firefly disappearances and citizen-science projects are documenting the phenomenon.

Ben Pfeiffer, founder of Firefly.org is worried about the decline of these insects.

"When people see a habitat that's got three, four, five different species of firefly flashing, each with a different flash pattern, it's an amazing thing. It changes their lives, but few people get to see that anymore," he said.

A combination of factors is threatening the insects. They include habitat degradation, pollution, endangered water tables and expanding pesticides, Pfeiffer added.

Fireflies play a useful role and exert multiple effects on ecosystems with some playing a role in pollination as in milkweed, wild sunflowers, and other species.

"I call them nature's pest control," Pfeiffer said pointing to firefly larvae which are avid predators of slugs, worms, aphids, and other critters.

Luciferin and luciferase — two enzymes created by fireflies in the bioluminescent flashes are also used in tracking the growth of cancer tumors and for detecting bacteria in food products.