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
         

Candid Camera: Using a trailcam to identify animals

Trailcam poised and ready to strike
Photo by Brad Sylvester, copyright 2011. Do not copy.

Last year, I spent about six weeks doing some volunteer work for a local conservation agency. As a thank you gift, they gave me a gift certificate to the Kittery Trading Post, an outdoor sports and recreation specialty store in Kittery, Maine. With the certificate, I bought a trailcam. A trailcam, for those who have never heard the term, is a camera designed to be left outdoors along a suspected game trail to photograph animals as they pass by. It uses a built-in motion detector to determine when animals pass by. Once the motion detector is triggered it snaps a photo. This particular model works in both daylight and in complete darkness as it has an infrared flash that enables night-vision photos.

The trailcam is an ideal tool to help me capture photos of the animals that live in my yard. It can be set up by a bird feeder to snap pictures of every bird that visits during the day, or it can be used to catch nocturnal or crepuscular creatures that live in my yard that I might never see myself. Today, though, I have set it up to try to catch a shy diurnal mammal that I know lives in my yard.

Stripped pine cones and loose scales mean that something
was eating pine seeds here.
Photo by Brad Sylvester, copyright 2011. Do not copy.

To determine where to place the camera, I look for clues like the one in the photo to the right. There are several pine cones here on the ground that have been stripped as some animal pulled them apart to get at the tasty pine seeds nestled inside the cone. I found a number of these pine cones around the base of a big tree, with many of the cones and associated debris on a large flat rock next to the tree. The rock makes a great lookout point from which a hungry, but wary little animal might work at the pine cone while watching all around for any threats. At other times it might take the pine cone up into the tree to eat in an even more secure location leaving pine cone scraps all around the base of its favorite tree.

I strongly suspect that this is the work of a squirrel. A chipmunk would also eat pine cones like this, but would most likely eat on the ground and not climb a tree for that purpose. Although it is not above using a tree to escape a predator, chipmunks are ground creatures. Their nests are burrows. Squirrels (with some exceptions), on the other hand, are more arboreal, which means they live in trees. They build nests in the high branches of a tree or a cavity in the trunk and raise their young there. They are more comfortable in a tree than on the ground and are more likely to take their food up into the canopy both to eat immediately and for winter storage.




Trailcam aimed at the base of a large pine tree in my
 front yard where the scraps of pine cones were
found in abundance.
Photo by Brad Sylvester, copyright 2011. Do not copy.

  Rather than placing a trail cam at any random location and hoping to catch something, finding clues that some animal frequents the spot first helps improve the odds of getting the picture you want. In this case, I set up the camera to aim at the base of the tree, on the side where the flat rock lies. The one thing I don't like about the camera is that there is a delay of a several seconds between the time when the motion detector is triggered and when the picture is taken. This is fine to allow larger, slow moving animals like deer to fully enter the camera's field of vision before it takes a picture, but for small, fast moving animals like squirrels, it can mean that they trigger the motion detector and are long gone before the picture is taken. We'll see how it works.

I'll post an update when I have some pictures to show of whichever animal has been eating the pine seeds. In New Hampshire, where I live, there are four species of "conventional" squirrels: the grey squirrel, the red squirrel, the northern flying squirrel and the southern flying squirrel. I say conventional squirrels because the woodchuck is actually a kind of squirrel as well, as is the chipmunk. I suspect the culprit in this case is either an eastern grey squirrel or a red squirrel.

Reader Question: Mystery Creature's Night Sounds

I recently received a question about a mystery creature in the comment section of one of the earlier posts on this blog and I wanted to share it and my reply with everyone:

Question:
"I hear a sound out of my 200 year old oak tree at night that sounds like clipping scissors. am suspecting it to be a squirrel. It's very sharp and keeps me up at night? am I right? What else could it be?"

Answer:
Some squirrels do indeed make a short, sharp high-pitched noise which is often regular in frequency for an extended period, perhaps every second or two. Most squirrels, however, are diurnal, sleeping at night. The exception is the flying squirrel (Glaucomy sabrinus or Glaucomy volans). Depending upon where you live, this might be the best possibility, although I don't know from first-hand experience what a flying squirrel sounds like. There are some birds and many insects that call at night as well, and these can't be entirely ruled out without more information. Try this experiment: place an 18" square piece of anything that's very flat and smooth (and preferably dark colored) out near the tree from which the sound originates. Sprinkle a light coating of talcum or other very fine powder evenly over the flat surface and placed a few peanuts, some peanut butter, or a crust of bread in the center of the board. In the morning, look for foot-prints in the talc. Flying squirrel feet would have tiny but well-defined finger-like toes. The front feet will leave prints almost like tiny hands and the rear feet will have pads that are a bit longer. Both prints may show evidence of the pointed claws they use for climbing. Use an online or printed animal footprint guide to compare against other small rodents which might be active at night.

You can also use an automatic trail cam to snap a picture of anything that comes to take the "bait" instead of using the tracking powder. If you place the baited platform several feet off the ground under the tree, you may also see evidence of the flying squirrel "landing" after leaping from above, providing even more evidence.

Mystery Creature Found Inside a Grape Tendril

Parasitized Concord grape tendrils
Photo by Brad yslvester, copyright 2011, all rights reserved

I have found my first mystery creature living in my yard. For lack of a better term, I’ll call it the grape tendril grub. I have Concord grapes in my yard and I noticed that two of the grape tendrils, located immediately adjacent to one another, had become bulbous at the tip. This is not typical of a grape tendril which is normally tendril-like in every respect, long, narrow, twisting and smooth. These two had tumor-like growths.



Normal Concord grape tendril
Photo by Brad Sylvester
copyright 2011, Do not copy.



Sectioned tendril showing the cavities and one grub
Photo by Brad Sylvester, copyright 2011. Do not copy.

My first thought is that it is either a fungal infection or an insect. Many insects will deposit their eggs inside the soft tissue of plant so that when the eggs hatch, the larva has a ready food supply and has some protection.

Small orange grub-like creature that was hidden inside
 the swollen grape tendril
Photo by Brad Sylvester, copyright 2011. Do not copy.

I examined the plant in the area of the misshapen tendrils and did not see any insect damage other than the expected Japanese beetle skeletonization of the larger leaves. Generally, though if a bug takes the time to lay eggs in or on a particular species of plant, that’s a bad sign for the plant as it almost always indicates that the larva will eat it. I’ll also note that this grape plant earlier had some spider mites which I removed with an application of soapy water.

I removed the two tendrils and cut the largest one open down the center with a very sharp knife. The largest of the two growths was an oval approximately 4mm X 8mm. Slicing lengthwise down the middle as you can see in the photo, uncovered two hollow pocket and resulted in a smear of orange paste on the knife blade. Oops. One of the pockets still had a bit of the orange color showing, but I apparently caught whatever was in the other pocket quite squarely with the blade, pulping it. I cut the other one open more carefully working in from the side so as not to repeat the mistake and discovered a very tiny orange grub-like shape inside the hollow of the smaller growth which was a sphere of approximately 3mm in diameter.

I rummaged around the house for a microscope some slides and some tools to help me handle and view the thing which was less than a millimeter in length and perhaps a third of a millimeter in width. Once I got it on the slide under a 50-75 power microscope lens, Its shape became clearer. It was definitely grub-like and was waving one end around in the air. As best I could count, it had thirteen ring-like segments. No other detail was readily visible, except that it was thickest toward the middle and tapered a little at either end.

The grub was colored orange as I’ve already mentioned, but to be more specific it was a bright yellow-orange like the skin of a pumpkin.

I can’t find this creature in any reference source. If I were to guess I’d say it’s reminiscent of a lady beetle larva, though very small like one of the Stethorus genus. It is possible that it’s in the pupal stage and not a larva at all. If so its appearance and size more closely aligns with Stethorus, but Stethorus would typically lay eggs on the underside of a leaf… Stethorus spp. would feed on spider mites, though.

What’s interesting about this insect is that it seems to change the plant behavior as well. The tendrils grow bulbous and thick with the plant’s own tissue, not just as a result of displacement caused by the insect’s growth. So either the grape plant is reacting in a defensive manner and has some kind of immune response to the presence of the insect inside it, or the grub is releasing some chemical that alters the plants growth. In either case, the result is a thicker, more secure case around the otherwise defenseless insect inside.

In any case, this one has to be filed under Mystery Creatures for now. I know it’s in the Class of Insects, and I suspect it’s in the Order Coleoptera (beetles), but even the Order is uncertain and I can’t get any further on this one at this point. Ideally, I’d find some more and let them proceed until they emerge from the grape tendril and see if they metamorphose into something recognizable.

NOTE: Kim Phillips, from one of my entomology groups on Facebook, suggests the Grape tomato gall (Lasioptera vitis). That seems like a definite possibility or perhaps (Schizomyia impatientis)?
NOTE 2: Got it, read the answer here!

Blooming Bulb has Concord Grapes if you'd like to add some to your yard.