Green Fig Beetle (Figeater Beetle/ Green Fruit Beetle) - Cotinis mutabilis

 

Green Fig Beetle (Cotinis mutabilis) flying over Yarrow in Mother Nature's Backyard

Have you noticed some large, bumbling green beetles in your yard recently?  They are most common from late July through September in the Los Angeles Basin - and so large you simply can’t miss them!  They’re raising quite a lot of interest now in Mother Nature’s Backyard.
 

The Fig Beetle is a true beetle, member of an extremely common group of insects (beetles account for about 1/5 of all animal species on earth).  Unlike other insects, the delicate inner wings of beetles are protected by a pair of tough outer wings,  the elytra.   When beetles fly, the elytra spread apart, allowing the membranous flight wings to unfold. 
 

The Fig Beetle is a scarab beetle (Family: Scarabaeidae), a group that plays an important role in recycling organic matter (more on that later).  More specifically, Green Fig Beetles are part of the subfamily Cetoniinae, commonly known as ‘fruit and flower chafers’ or ‘flower beetles’.  Unlike most scarabs, the ‘flower beetles’ are often brightly colored and active during the day.  Not surprisingly, adult ‘flower chafers’ are often seen feasting on flowers and fruit.

 

The Green Fig Beetle is native to Southwestern U.S. and Mexico.  The species was likely limited to moister areas of Arizona, New Mexico and northern Mexico in the past.   But Fig Beetles have increased their range, first becoming noticeable in coastal Southern California during the 1960’s.  They now range further up the California coast and into the Great Central Valley as well.  While cactus fruit and the sap of desert trees comprise their native diet, Fig Beetles now feed almost exclusively on garden and agricultural fruits.

Green Fig Beetles are large (up to 1.25 inches (3 cm) – in fact they are one of our largest native beetles.  They are often mistaken for Green June Beetles (Cotinis nitida) and Japanese beetles (Popillia japonica).    The Figeaters are noticeable larger than June and Japanese Beetles, which are mostly confined to Eastern United States.  And they don’t damage lawns and fruit crops to the same extent as their eastern relatives.  In fact, Figeaters are not considered an important pest species and are not controlled in California.
 

Green Fig Beetles are velvety green above and
 metallic green below

Figeater Beetles are dark, velvet green on top, with a cream-colored band around the edge of the elytra (see above photo).  Their legs and undersides are a brilliant iridescent green.   The head has a short, hornlike projection in the front and their legs have hooks for grabbing onto flowers and fruit (see photo below).   They are slow fliers and often collide with large objects including walls, houses and even humans. 
 

Figeater Beetle (Cotinis mutabilis) clings to stem of a Yarrow plant (Achillea millefolia)

Flying Figeaters make a loud buzzing sound.   The sound is likely produced by the Fig Beetle’s elytra, which are partially closed in flight and are only barely raised during takeoff.  You can actually see the partially-open elytra in flight – they are truly slow fliers.   The Figeater’s armor (the elytra) does provide protection, but it also makes for clumsy flight!
 

Green Fig Beetles don’t bite and are relatively unbothered by humans.  This makes them an excellent species for close observation (they are great for teaching children about beetles).   They are fairly easy to photograph; you can sometimes even get them to remain in your hand for a short while.  Treat them gently and with respect; they are living creatures with a role to play in the garden. 
 

Green Fig Beetle - Cotinis mutabilis

As in the wilds, adult Figeasters emerge in mid- to late summer, when their food sources are at their peak.  In the Sonoran Desert, their emergence coincides with the summer monsoons, when cactus fruits ripen and sap flows from the Velvet Mesquite (Prosopis velutina) and Desert Broom (Baccharis sarothroides).   This is also when Fig Beetles gather in shady areas to complete their simple courtship.  The competition between Figeaters can sometimes be fierce; see http://arizonabeetlesbugsbirdsandmore.blogspot.com/2011/08/fighting-fig-beetles-cotinis-mutabilis.html

Adult Figeaters have a real sweet tooth – they are attracted to anything sweet, including some leaves, flowers, sweet sap and ripe/over-ripe fruit.    They cannot bite through the tough skins of many fruits; they usually eat fruits that have been damaged by birds/insects/squirrels – or are over-ripe.   Figeaters are attracted by the gases emitted by ripening and fermenting fruits, which serve as an airborne signal.  Among their favorite fruits are apricots, pears, peaches, apples, figs, melons, grapes, nectarines, tomatoes and of course, cactus fruits.   

In many gardens, adult Fig Beetles do little damage (compared to birds and pesky squirrels).  However, they can swarm on soft or damaged fruit and have been known to eat an entire garden grape or fig crop.  The best prevention is regular harvesting of ripe fruit.   Daily fruit harvest is often enough to limit predation to a tolerable level.  If your garden has many Fig Beetles, or if they are still eating your fruits, you may want to take some other, relatively simple steps.

The increase in Figeater Beetles is due in large part to the spread of home gardens.  Abundant adult food plays a role.   But many local gardens also provide choice larval food for Fig Beetles: compost, composting manure and organic mulch.   Adults lay their eggs in the decomposing material in the fall.  The beetle larvae then feed on the decomposing matter through winter and spring.  In fact, the larvae are important ecosystem ‘recyclers’, along with soil bacteria & fungi.  
 



Photo courtesy of Wikimedia: http://commons.wikimedia.org/wiki/File:PC180002JuneBeetleLarvae_wb.jpg


 If you live in Southern California you have likely encountered Green Fig Beetle larvae while turning your compost or reapplying mulch.   They look somewhat like large (up to 2 inches), fat, pale caterpillars (see above).  At rest, they curl up into a stiff C shape.  When disturbed – or to move – they roll over onto their backs and propel themselves using stiff, dark back ‘hairs’ and muscle contractions.  The common name ‘Crawly Backs’ reflects their mode of locomotion; the small legs are not used for movement.

Green Fig Beetles have a single generation per year in local gardens, although they may remain in the soil for two years if food and water are scarce.   Larvae typically emerge from the eggs in fall.   They live deep in the soil/compost during winter and early spring, eating and growing.  Hungry Crawly Backs occasionally consume plant roots, but their primary food is decayed plant matter.   Like most larvae, they eat a lot – they literally are ‘eating machines’.  They provide a vital service by hastening the decomposition of organic matter and aerating soils and compost.    Can you image a garden with no decomposition?  Ugly thought!

In spring, the larvae migrate upward to begin their second larval stage.  They can often be found feeding near the surface and you’ll sometimes see small mounds of soil near the entrance to their tunnels.  This period may have consequences for the home garden.   Larval tunnels can cause the soil to dry out around plant roots.  And the extraction of larvae by several common mammals can leave gardeners at their wits end.   In Mother Nature’s Backyard, raccoons, possums and skunks often dig up the large larvae and eat them.     Excavated holes in organic mulch or a lawn are a good indicator that Crawly Backs or other larvae are being eaten in your garden.  

In late April or May, Figeater larva create an underground pupal chamber with walls composed of sand particles and frass (solid excreta).   The larvae pupate (metamorphose from larval to adult form) in the pupal chamber, emerging as winged adults in summer.   And so the cycle continues. 

If Green Fig Beetles are a problem, consider trying to control them during the larval stage.   Turning over compost piles more frequently can help, as can letting your compost pile heat up.   Some gardeners screen their compost before using it; the larva can be returned to the compost pile if desired.    If you have a horses, know that manure piles can harbor Fig Beetle larvae as can thick layers of organic mulch.   For UC Pest Management Guidelines regarding this species see: http://www.ipm.ucdavis.edu/PMG/r261300511.html

We encourage your comments below.   If you have questions about Green Fig Beetles or other gardening topics you can e-mail us at :  mothernaturesbackyard10@gmail.com