In last week’s episode, we visited small wolf spiders, beneficial predators and amusing invaders of the Bug Guy’s home. This week we visit a cousin of the iconic firefly called the soldier beetle, a.k.a. leatherwing. Both fireflies and soldier beetles belong to a group of beetles in the superfamily Elateroidea that also includes click beetles and several other related families. Over the past several weeks, I have received emails with images attached of soldier beetle larvae, also known as velvet worms, that have entered homes or been seen dashing across sidewalks. Like other members of the elaterid clan, soldier beetles are natural born killers in both adult and juvenile stages and are highly beneficial rascals to have around the garden.
Juvenile stages are dark grey larvae cloaked in thick, velvety coats of fine hairs that give them their common name. They are important predators of ground dwelling insects and can be found up in plants, where they have ascended from the earth to find prey in flowers and on fruit and foliage. I often see large numbers of these hairy rogues in autumn hunting in flowerbeds or on sidewalks and patios. Soldier beetle larvae visit homes in fall when they squeeze beneath the door sweep. When I find them inside, I simply pick them up and return them to the wild. For soldier beetles in Maryland, the larva passes the winter in soil, under leaf litter, or beneath loose bark. A renaissance in fireflies that was seen in the DMV this summer seems equaled by soldier beetles, which appeared in impressive numbers on the blossoms of perennial plants in my flowerbeds. When not consuming nectar and pollen, adults dine on plant pests such as aphids and caterpillars.
Whether searching a leaf for aphids, hunting grubs in a flower bed, or dashing across a patio to escape a nosy bug geek, soldier beetle larvae are fun to watch.
Mating antics of soldier beetles seem to occur almost nonstop and are quite entertaining. Their rambunctious behaviors have been the subject of several studies. In the soldier beetle dating game, size does matter. Witness the goldenrod soldier beetle, Chauliognathus pennsylvanicus, where biologists discovered that mating females and males were significantly larger than their smaller and less fortunate, non-mating counterparts. It turns out that female soldier beetles are choosy lasses and exercise their prerogative to accept or reject a potential mate. The advantage to large size in males is not so much a “big guy, good look” feature that attracts the females. Apparently, large size enables an amorous male to subdue a coy female beetle more effectively than his smaller competitors, whose attentions can be more readily dismissed by the discriminating lady. Irrespective of how they play the dating game, last year must have been a very good year for soldier beetles based on the remarkable numbers found in our gardens and landscapes this year. Let’s hope this trend continues for all of the Elateroidea clan.
A female soldier beetle multitasks with her mate while searching for food on a flower head.
Bug of the Week thanks Mike Murillo for providing an image and inspiration for this week’s episode. The interesting article “Density Dependent Sexual Selection and Positive Phenotypic Assortative Mating in Natural Populations of the Soldier Beetle, Chauliognathus pennsylvanicus” by Denson Kelly McLain was used as a reference for this episode.