This week we were grubbing around in the compost heap when we found this. We were quite excited.
It’s about the size of my thumb. I can tell it is a beetle larva from the fact it has a hard head capsule (dark brown) and six distinct legs right behind its head. Those small brown circles on its sides are the opening of the airways it uses to breathe. Those are called trachea.
I knew what kind of beetle it was when it flipped onto its back and began crawling along upside down. My son said this was “Freaky!” (I think that is tween-speak for “Really cool!”) You can see the legs better. It also has bristly brown hairs. It quickly crawled off, upside down.
This interesting critter is a green June beetle grub, Cotinus mutabilis. They are a type of scarab beetle. The larvae (grubs) feed on compost and help with decomposition. They are up to two inches long when mature. Next Spring it will pupate in the soil and emerge as an adult.
The adults have beautiful metallic green wings with brownish-gold at the margins. They congregate in large numbers to feed on various types of soft fruit, which gives them their other common name, figeater beetle. Their normal food in Arizona is prickly pear or saguaro cactus fruit. They also visit our desert willow flowers for nectar.
I only have a photo of a preserved specimen. Don’t worry, all of our preserved bugs died of natural causes.
The adults are even shinier when they are alive. Isn’t it interesting such a “freaky” larva can turn into such a spectacular adult? Talk about the ugly duckling…
By the way, if this grub hadn’t scooted away so quickly, it would probably have been bird food. Grackles love them.