Ladybug mom provides infertile eggs as baby food.

When food gets scarce, ladybugs lay extra dud eggs that can end up as emergency rations for youngsters that do hatch.

"Ladybugs are really cannibalistic at lots of life stages," says Jennifer C. Perry of the University of Toronto. Larvae often eat infertile eggs as well as eggs that would have developed into their siblings. Perry says that she wondered whether the nonviable eggs were just fertility glitches or an adaptation to food shortages.

She tallied the eggs laid by female multicolored Asian ladybugs (Harmonia axyridis) given plenty of aphids. After the ladybugs reached peak health, she skimped on the rations for some of them for 24 hours.

Ladybugs experiencing a day of scarce aphids produced a higher proportion of infertile eggs than well-fed ones did: 23 percent versus 15 percent, Perry reports. She doubts that sheer physiological depletion caused the jump in dud eggs, she says, because earlier lab experiments had shown that ladybugs can go for more than a month without starving.

Instead, the increase in infertile eggs supports the idea that ladybugs tailor their egg laying to the conditions their young will face, Perry and Bernard Roitberg of Simon Fraser University in Burnaby, British Columbia, suggest in an upcoming Behavioral Ecology and Sociobiology.--S.M.