This bug’s all-in helicopter parenting reshaped its eggs

Parents will fret, even among bugs. And even among bugs, it’s complicated.

Ferociously protective parenting has evolved four times among the pointy-faced, wide-bodied little leaf dwellers called shield bugs, researchers report in the May Biological Journal of the Linnaean Society. Those shifts from zero to all-in helicopter parenting affected egg shape, analysis of 30 species shows.

For the new study, behavioral and evolutionary ecologist Shin-ichi Kudo and colleagues watched shield bugs (Acanthosomatidae), measured over 1,400 eggs and considered the insects’ evolutionary tree. Attentive parenting didn’t make much of an impact for species with the biggest eggs, which generally stayed round, the analysis shows. For the rest of the species, however, the rise of vigilant moms tended to be followed by rounder eggs elongating into more of a pudgy barrel shape that can pack tight under mom’s body.

Moms became attentive although not awesomely armed. “Mothers cannot bite,” says Kudo, of Naruto University of Education in Japan. They don’t have jaws. Instead, a soda straw–style mouthpart works well for tapping veins in plant leaves to feed on but isn’t much help against ants scouring for food.

Instead, a guarding mother bug body blocks and fusses. Laying eggs in a tight array, often on a leaf underside, she straddles the tightly packed clutch. Should a passerby show too much interest in helpless eggs, she clarifies that first, intruders must subdue her. And that she won’t make it easy. She starts by “jerking, tilting the body toward the disturbance and fanning wings,” Kudo says.

For insects, this study is the first to link changing egg shape and evolution in parental care, Kudo says. Bird egg shapes have long fascinated scientists, and a link between shape and bird parenting has shown up. Kudo says he has wanted to test the idea in shield bugs since his first sighting in the field of moms straddling “dense and compact egg masses.”

Parental tending of any kind shows up only in about 1 percent of known insect species, Kudo says. Bees and ants, hatched helpless, may pop to mind as familiar examples. Yet for an insect audience, those bees and ants — plus humans ourselves— would be quite the oddities.