Helicopter cockroach moms have protected their young for millions of years
Very early on, cockroach moms found out maternal care gave their offspring a better chance at survival.
The cockroach parenting method—which includes feeding, guarding and keeping their young very close—has served the insects for at least 125 million years.
A team of scientists from China and the U.S. has uncovered new fossil evidence of one of the earliest devices used by a mother insect to protect and transport her young—an egg case called an ootheca.
Fossils from China that are 125 million years old clearly show an ootheca protruding from the abdomen of a female Piniblattella yixianesis, a previously unknown and long-extinct species of cockroach.
Leathery and long, the ootheca is a capsule that emerges from the female’s abdomen partitioned into 60 to 70 compartments, each containing an egg that hatches into a nymph before the ootheca opens. It enables a cockroach mom to protect her young 24/7 and is one reason that today cockroaches are a diverse and successful insect group that has invaded almost every habitat on the planet.
“Cockroaches adopted inconspicuousness—coming out only at night and feeding on waste—as a response to this huge increase in hungry, insect eaters,” Labandeira says.
At the same time, cockroach maternal care also ticked up a notch. Rather than laying eggs and leaving them behind with the potential to be devoured, cockroach moms developed an ootheca and began carrying their eggs with them everywhere. They would leave behind oothecas filled with newly hatched nymphs in a dark, hidden place to break open and allow the nymphs to escape unseen.
Moist on the inside, the ootheca case also prevented eggs from drying out. Being buried in the fermenting decay of leaves and wood prevented damage from excessive cold and heat.
Cockroaches continue to be good moms at mealtime as well, Labandeira says.
“If the mid-Mesozoic fossil record of cockroaches was better, Labandeira adds, “we probably could track the origin of ootheca back millions of more years, maybe as far back as the Late Jurassic,” or about 165 to 145 million years ago.