Praying mantid: Scary -- if you're an aphid

Praying mantid molts off its old exoskeleton and emerges as an adult. (Photos: Debbie Arrington)

With a big appetite, this garden predator also eats beneficial bugs

By Debbie Arrington

Love them or hate them, this critter ranks among the scariest-looking insects in the Sacramento garden -- especially when it sheds its skeleton.

With their large forelegs, praying mantids were made to grab prey (not prayers). They're typically considered "ambush" predators, latching onto anything that happens into their path.

Their appetite for aphids makes them a garden "good girl." But they are lazy and indiscriminate hunters; they can eat beneficial insects, too. Because they like to hang around flowers, they often catch nectar- or pollen-feeding insects such as butterflies.

"As mantids consume both pests and beneficials, they are difficult to use reliably for biological control," say the UC Cooperative Extension master gardeners.

How they hunt is fascinating. Like a chameleon, they change color to blend in with their surroundings. Then, they sit and wait for unsuspecting dinner to wonder by. Their bulging eyes give them stereo vision that pinpoints their prey; their flexible little necks can spin their triangular heads almost 180 degrees. 

When it's time to strike, they spring quickly into action, seizing their quarry with those monstrous forelegs. 

Otherwise, they move very slowly, or not at all.

The praying mantid, fresh from its old exoskeleton.

Although usually called "praying mantis," mantid is the proper name, reflecting their largest family, Mantidae. More than 2,400 species of mantids and their close relatives are known.

The species that prowls Sacramento gardens reaches about 4 inches long at maturity. It has only one generation per year.

During these late summer months, the mature adults come out in force. While hanging upside down, they molt their exoskeleton (their "skin").

"All insects molt during the immature stages as they mature," explained retired state entomologist Baldo Villegas, Sacramento's Bug Man. "There may be from three to four immature stages or molts."

During this heat wave, a mantid outside my home office window shed its exoskeleton, which looked like a ghost bug hanging on the stem beside it. The fully developed adult mantid emerged, probably hungry.

That's OK, she can have all the aphids she wants. But leave the butterflies alone.