While the autumnal onslaught of stink bugs continues, we turn our attention this week to soldier beetles. Earlier this year in an episode entitled “Soggy death to friendly soldiers” we visited the goldenrod soldier beetle and its deadly fungus. This week we revisit this interesting beetle whose larvae are very abundant in late summer and early autumn. Soldier beetles belong are a group of beetles in the superfamily Elateroidea that also includes click beetles and several others related families. Like other members of this clan, soldier beetles are natural born killers in both adult and juvenile stages and are highly beneficial rascals to have around the garden.
In autumn, velvety soldier beetle larvae hunt for prey in flower beds, on vegetation, and on paved surfaces.
The juvenile stages are dark grey larvae cloaked in a thick, velvety coat of fine hairs. They are important predators of ground dwelling insects and they will ascend plants to find prey in flowers and on fruit and foliage. Over the past several weeks, large numbers of these hairy rogues have been seen 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 larvae pass the winter in soil, under leaf litter, or beneath loose bark.
This year seems to have been a sort of renaissance for solider beetles, which appeared in record numbers on blossoms of perennial plants in my flowerbeds. When not consuming nectar and pollen, adults dine on plant pests such as aphids and caterpillars. 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. 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 dismissed by the discriminating lady. Irrespective of how they play the dating game, recent years must have been very good 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 nectar and pollen on a flower head.
Bug of the Week thanks Dr. Shrewsbury for providing 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.
To learn more about soldier beetles, please visit the following web sites: