Wireworm (Click Beetle Larva) Identification Notes

Underside of the head of a wireworm (click beetle larva)
Photo by Brad Sylvester, copyright 2012

One of the things I really enjoy about the "What Lives in my Yard?" project is that it forces me to take a closer look at the animals I find and to discover relationships between them (and the flora of my yard). For example, as a kid growing up in New England, click beetles are quite familiar. I recall finding them and placing them on their backs and waiting for them to "click." The unleashed elastic force of their click would not only make an audible noise, but would pop them quite high up into the air.

As an avid gardener, I am also familiar with wireworms. The hard-bodied, little, orange caterpillar-like larvae that are often found in garden soil that is rich in organic material. I never would have suspected that they were actually the same animal. Wireworms are click beetle larva.

Wireworm measuring 26mm (1") in length
Photo by Brad Sylvester, copyright 2012.

I am sure that I have click beetles on my property here in southern New Hampshire. I have seen click beetles here, but don't recall specifically seeing any other species. At any rate, I'll need to identify the larva itself, and then look for the specific adult form of the same beetle later in the season.

I can start with the click beetle family (Elateridae) and work down the taxonomy tree from there. There are seven sub-families of Elateridae listed at Bugguide.net. Clicking on these, however, nets us photos of adult click beetles, and while bugguide.net does have some pictures of click beetle larvae, there are relatively few with positive identifications and I could not find a single one that matched the tail appendages of my specimen.

Top view of the tail end of the unknown wireworm
Photo by Brad Sylvester, copyright 2012.

One of the first things that I discovered as I began searching through other sources is that wireworms are a significant agricultural pest. The larva live and feed in the soil for 2-5 years before pupating and turning into an adult click beetles according to an Oregon State University web page. They eat roots, tubers, germinating seeds, and sometimes other insects and can cause significant damage to garden crops such as peppermint, potatoes, corn, strawberries and other food crops. Note that this particular specimen was found in the soil of what was a strawberry bed ( a fact which may help in the identification).

As an agricultural pest, of course, pesticide manufacturers are among the major sources of information about this insect. Syngenta has a complete field guide for wireworms detailing their behavior and life cycle along with copious amounts of data about almost every aspect of their existence --except determining exactly which species they are. As far as the Syngenta guide is concerned, wireworms are wireworms and they're all bad. This is despite the fact that the majority of wireworms eat decaying matter and a few eat other insects.

Side view of tail end of wireworm showing a single, central
proleg
Photo by Brad Sylvester, copyright 2012.

Interestingly, though, once they do pupate and metamorphose into click beetles, they cease to be a problem and no longer eat agricultural crops at all. Syngenta also provides a simple technique for determining whether you have wireworms in your fields. Just plant a small ball of dough and check it a few days later. Wireworms, they say, are attracted to CO2 emitted by the dough or by germinating seeds. I might try this one day to see if I can find more than one species of wireworm.

Another problem with trying to identify insects using field guides like the National Audubon Society Field Guide to North American Insects and Spiders  is that they are not truly comprehensive in scope. They may list a few representative species from a taxonomic Family or Genus, but many are left out. From my own experience, I know that the Eyed Click Beetle is not the only one found here, but it is the only one listed in the Audubon guide.

This wireworm had one set of legs on each of the first three
segments after the head.
Photo by Brad Sylvester, copyright 2012.

According to Majka and Johnson as published in Zootaxa, however, there are 965 individual species of Elatiderae in North America of which only about 20% have described larva. Granted that not all of them are found in New Hampshire (Majka and Johnson list 91 New Hampshire click beetles) that still leaves a lot of work (and perhaps a nearly impossible task) for an amateur entomologist like myself in trying to identify the one specific species I have found, especially since it is a larval form.

The personal web page on wireworm research of Wim Van Herk, says "A little research into the classification of the Elateridae will likely lead to both confusion and frustration." Herk notes that depending upon which expert one consults, Elateridae are divided into either 3, 7, or as many as 18 subfamilies.

Face of the wireworm
Photo by Brad Sylvester, copyright 2012.

One way to identify an insect when you have only a larva and only have resources to identify the adult form, is to keep it alive in captivity until it metamorphoses into the adult form. When it spends 2-5 years in the larval form, however, that can be problematic. Another option might be to look and see where I found the larva to see if I can find adult beetles as well. The research suggests that adults will often be present overwintering in the same locations as the larva, although that would be more circumstantial than conclusive evidence. I could also keep the wireworm in captivity and offer it several food sources, strawberry roots and grubs, for example to determine what this particular species eats, which might narrow down the choices.

It seems that wireworm or click beetle larva species identification is a highly specialized field and certainly beyond my skills at present. I have, however, included some photos that show details an expert might use to identify the specific species, if you know one, please send them this way.

The best I can do for now (with help from bugguide.net) on the taxonomy of this wireworm is:

Side view of wireworm showing spot, vertical line, and
horizontal crease on each body segment
Photo by Brad Sylvester, copyright 2012.

Kingdom: Animalia
Phylum: Arthropoda
Class: Insecta
Order: Coleoptera (Beetles)
     Sub-order: Polyphaga
Superfamily: Elateroidea (Click beetles, fireflies & soldier beetles)
     Family: Elateridae (Click beetles)
          Subfamily: unknown
Genus: unknown
Species: unknown