Bug o’ the Week – Checkered Beetle

Salutations, BugFans,

 

The BugLady chased this speedy little Checkered beetle (probably Enoclerus rosmarus) around a wild sunflower stalk for a while, and these are the best pictures she could get.  When she first saw it out of the corner of her eye, she thought that it was a particularly colorful ant, and that’s the point.  There’s a group of wasps called “Velvet Ants” whose females are wingless (and furry) http://bugguide.net/node/view/956650/bgimage.  They occur in dry, sandy areas from the Southwest and southern Great Plains, through the Gulf States and up the Atlantic coast as far as Connecticut (the BugLady has seen them in Texas and southern New Jersey).  The fact that they are also called “Cow-killer ants” hints at how their sting feels.  This genus of checkered beetles has picked a good group to mimic, because nobody messes with Velvet Ants.

 

About 300 species of checkered beetles (family Cleridae) live in a variety of habitats in North America (there are about 3,500 species worldwide).  As a group they are small-ish, hairy, long and narrow, and brightly-patterned.  Their head is wide, their thorax tapers, and the elytra (hard wing covers) are broader than the thorax.

 

CBs can be seen on flowers and in trees.  Most species are meat eaters as both larvae and adults.  Adult Clerids practice their carnivorous lifestyles in a variety of ways – the majority hunt on and under the bark of trees; some sit on flowers or sap flows and prey on visiting insects (they occasionally stop and sip the nectar and pollen themselves; adults of some species eat it exclusively and are considered noteworthy pollinators).  Still others consume insect eggs.  There are a few scavengers in the bunch, too, and some that “prey on” processed foods or on pests of processed foods.

 

Some of the under-the-bark species are considered important biological controls of the bark and wood-boring beetles whose galleries (tunnels) devalue cut timber.  If, like bark beetles, you live under bark, in the dark, you can’t use visual signals to find a mate.  You can use chemical signals called aggregation pheromones to gather a like-minded crowd, and the clever CB can tune into these pheromones to locate its meals.  Clever foresters can buy synthetic bark beetle pheromones and deploy them to attract more Clerids.

 

In general, adult CBs eat adult beetles, and their larvae feed on beetle larvae.  Ralph Swain, in The Insect Guide, calls CB larvae “the ferrets of the insect world, preying upon the larvae of bark beetles and other wood-boring beetles, moths, wasps and bees” (they can be a problem in honeybee hives), and even on gall insects.  They are able to excavate their own tunnels but are more likely to follow their prey down its tunnel.  The larvae of vegetarian CBs tend to be scavengers.

 

Females lay their eggs, a few dozen at a time, usually under the bark of a dead/dying tree that contains their larva’s prey, or in the soil.  The larvae are described as vigorous feeders – indeed, egg-laying requires so much energy that females often eat vigorously even as they’re mating.  CBs tend to overwinter in the larval stage, pupating in spring in cells they prepare in the soil or in their prey’s tunnel and emerging in summer.

 

Enoclerus rosmarus (no common name) is just under a half-inch long, covered with bristly hairs that are more dense aft than fore.  It lives in the eastern half of the US and its range extends south into Central America.  Unlike its tree-loving relatives, Er loves flowers and is found on a variety of prairie plants (one study linked them with horseweeds in the genus Conyza) and sumac, and its favorite food is nectar.  Er larvae overwinter burrowed into the stems of prairie plants, especially those in the Aster family.

 

As alert BugFans have probably noticed from the BugLady’s verbal tap-dancing, there was a dearth of specific life history information about this lovely species, but its name did come up in tantalizing references from a variety of research projects:

  • In a study by Senchina and Summerville to enumerate the insects that are associated with poison ivy.  Apparently, poison ivy is an under-studied plant (go figure!) but the Er was one species of the 37 “floral associates” noted during the study.  Poison ivy’s multitude of pollinators help it to spread.
  • Ers apparently overwinter as “inquilines” (Latin for “boarders”) in a rose stem gall (scientists bring a gall inside in the winter, put it in a screened container, and record who eventually emerges – besides the gall-maker itself.  In one study involving Willow pine cone galls, 23 galls were collected, and 564 insects were reared from them – but only 15 of the galls contained the original host gnat) (some inquilines live not-so-peaceably with their hosts).  Ers were also reared from several oak galls; a few CBs feed on gall-makers, but it wasn’t clear if the Er’s were dining, or just using the guest room.
  • In a publication called “Fauna Overwintering in or on the Stems of Wisconsin Prairie Forbs” (wildflowers), Williams reports that Ers and a surprising number of other arthropods – adults and immatures, from several rungs on the food chain – overwinter on or within the stems of Joe-Pye weed, Blazing star, etc.  This becomes important as prairie management techniques are selected – fire, mowing and grazing are hard on these highly specialized prairie invertebrates.  As Riveredge’s Andy Larsen used to say, you can try to establish a prairie, but until the sustainable partnerships of native plants and-insects are in place, all you have is prairie plantings.

 

The BugLady