The Mason Wasp Euodynerus foraminatus Endorses Bee Blocks

Those "bee blocks," chunks of wood with holes of varying diameters drilled into them, are all the rage now for attracting solitary native bees like leafcutter bees and mason bees. They do work, no matter where you live, and I have proof. Ok, so the first occupant in our newly-hung bee block is actually a wasp, but that is also a good thing, and I'll explain why.

A bee block need not be as fancy as the one shown here. There are some standards you should adhere to, though, and a thorough explanation is found here. Solitary bees come in a variety of sizes, so having a good selection of various diameter holes is helpful.

Why am I excited that a solitary wasp is using our block? Wasps are "flower visitors" that go to flowers strictly for nectar to fuel their activities (think gas station, not grocery store), but they do a fair bit of pollinating in the process. The biggest benefit of wasps, though, is that they are parasitoids of insects we consider pests.

The scenario for the mason wasp using our nest box, Euodynerus foraminatus, goes like this: The female wasp catches and paralyzes a caterpillar, and flies it back to the nest hole where she stashes the victim, and usually several more, as a larder of food for a single larva offspring. She lays an egg on the first or last victim, and then erects a mud partition. She repeats the steps, such that one of those holes you drilled might end up filled with several cells, each holding numerous caterpillars that won't be eating your garden plants. The preferred prey of E. foraminatus are larvae of moths in the families Oecophoridae, Tortricidae, Gelechiidae, Pyralidae, Crambidae (subfamily Pyraustinae). All of these include some notorious pests, as well as caterpillars that conceal themselves in rolled or tied leaves that other wasps won't go to the trouble of extracting.

We know at least one nest tunnel is complete because it has been plugged with mud. You can identify the different types of bees and wasps using a "bee condo" by the kinds of closures they make. Some megachilids (mason and leafcutter bees) will make the final closure with a plug of chewed-up leaves. Other bees will plug a nest hole with plant resins.

Besides the comings and goings of the bee block inhabitants, you can get some other kinds of drama. While watching the bee block for signs of activity last Friday, I noticed a crab spider hanging out under the "eave" on our bee block. Sure enough, when the wasp approached the spider reacted, hanging of the roof and opening its "arms" in a potentially lethal embrace. The wasp ignored or never noticed the threat, but I ushered the spider to another part of our yard anyway.

You may think that there is no way one of these boxes would work in your yard. The above image is of our yard, behind our townhouse unit. Look at it! It is literally like ten-by-twelve feet. Surely, if we can make this work, so can you. It takes virtually nothing to put one up, and it offers both critical bee real estate for the insects, and hours of entertainment for you and your family. Since solitary bees and wasps do not have vast quantities of offspring and honey stores to defend, they are not going to sting you. Besides, they are too busy working.

Back to that mason wasp for a second. Euodynerus foraminatus is a very widespread species, found coast to coast in the United States, plus all Canadian provinces, and down into Mexico, too. There is a very good chance you could attract one to your own bee block.

Sources

: Buck, M., Marshall, S.A. and Cheung D.K.B. 2008. "Identification Atlas of the Vespidae (Hymenoptera, Aculeata) of the northeastern Nearctic region," Canadian Journal of Arthropod Identification No. 5: 492 pp. (PDF version).
Stone, H.B. 2014. "Insects of the Week: Eumenids and Chrysidids," The Bees' Needs Blog.

Jumping Spider, Phidippus insignarius

While exploring Cheyenne Mountain State Park on June 3, I caught glimpse of a very colorful jumping spider prowling a dead thistle stalk among some branches of scrub oak (Gambel's Oak). My first thought was it must be a male Phidippus of some kind, but I am used to them being a fair bit larger than this one was. Well, I was excited to find out later that it was indeed a male Phidippus insignarius.

The crazy thing is, I was already familiar with that species, thanks to some simply stunning images by Patrick Zephyr and Raed Ammari. I only remembered these head-on pictures, and forgot what the whole spider looked like.

I had also forgotten, or never knew, that P. insignarius is found here in Colorado. Indeed, it ranges from here east through Nebraska, Iowa, Kansas, eastern Oklahoma, Missouri, southeast Minnesota, Illinois, Indiana, Kentucky, Tennessee, Pennsylvania, southern New England, New Jersey, Virginia, and North Carolina. Look for it in the understory of open woodlands and prairies. The oak thicket with scattered pines in an otherwise grassland habitat where I found this one seems to be the ideal habitat.

P. insignarius is not a terribly large spider. Mature males average just under 5 millimeters in body length, females 5.45 millimeters. The coloration of the female, from all I can gather, is similar to the male, but without the bright white hairs on the carapace, legs, and palps. Both genders have the bushy "eyebrows" that are characteristic of many Phidippus species.

If you are all ready to go searching for jumping spiders now, consider investing in a "beating sheet," or make your own. A friend of my wife who is an accomplished seamstress, whipped one out for me in no time. We chose a heavy, durable canvas (still prone to deformation with a good stiff breeze), about two feet square. Triangular pockets in each corner receive wooden slats arranged in an "x" pattern with a screw in the center to join them.

Beating sheet in use ©knoxnews.com

The beating sheet is held under the branch of a tree or shrub, and a heavy stick or rod is used to sharply strike the branch. All manner of spiders, and insects, of course, can come raining onto the sheet. This is the best way to collect many cryptic arthropods that are seldom seen otherwise.

Sources: Edwards, G.B. 2004. "Revision of the Jumping Spiders of the Genus Phidippus (Araneae: Salticidae)," Occasional Papers of the Florida State Collection of Arthropods. Volume 11. 156 pp.
Hollenbeck, Jeff. 2007. "Species Phidippus insignarius," Bugguide.net

Louse Flies? Are You "Ked"-ing Me?

Until recently, insect diversity here along the Front Range of Colorado this spring has been suppressed by cool, wet weather. How amazing, then, that I should see not one, but two specimens of an insect I had seen only once or twice in all my years. I am speaking of "louse flies" in the family Hippoboscidae.

Back at the end of December in 2009, I volunteered to do a guest blog for my good friend Dave Small after he sent me an e-mail inquiring whether I might know the identity of an insect in an image he attached with his message. I didn’t quite understand the story at first, like why two hunters were involved, and why the insect was adhered to hard candy. The image was clear enough, though, that I could tell what the creature was, and that this was not a tall tale evolved from heavy drinking. Here is the rest of that piece.

Deer and related animals play host to a variety of parasitic invertebrates, including the familiar, slow-moving ticks. Such blood-feeding creatures are quick to abandon a deceased host, however, and so animals harvested during the hunt often yield some strange, living cargo during inspection and dressing.

The specimen discovered by these two hunters is an insect known as a “louse fly,” among the most peculiar of insect parasites. They are much more nimble than ticks, dodging attempts to catch them as they skirt through a host’s fur. Their flattened shape, top to bottom, and talon-like claws enhance their ability to slip between hairs and grip the hide of the host, avoiding licking and biting efforts to dislodge them.

Members of the fly family Hippoboscidae, most known louse flies are actually parasites of birds. The most infamous member of the family, though, is the “sheep ked,” well-known to those who manage flocks of ovine livestock. The adult flies are wingless, but they find each other easily for mating when the host animals crowd together.

Back to the specimen the hunters found, and collected by sticking it with a piece of hard candy. That would probably be a “deer ked,” Lipoptena cervi. Here is a terrific image of a related species, Lipoptena depressa from northern California. Both species have a life history that is typical of the entire family of louse flies, but truly mind-blowing compared to other insects.

Female louse flies do not lay eggs. They grow one offspring at a time, within their bodies, much like mammals. A single larva develops inside the equivalent of a uterus, feeding from a “milk” gland. When mature, it is “born alive,” dropping to the ground where it immediately buries itself and pupates. An adult fly emerges weeks later. Deer ked are winged, at least initially, but females that have found a host will break off their wings, the better to maneuver through the dense, coarse hair of their host.

Wingless deer ked after two days in captivity

While keds are known to transmit certain diseases from host to host, they are for the most part not economically important. Consequently, little is known about them. Kudos to our hunter friends for bringing this one into the spotlight.

The first specimen I found this year landed on my while I was hiking in Aiken Canyon Preserve off of highway 115, about fifteen miles northeast of Penrose, Colorado on Memorial Day (May 30). I recognized it fast enough to grab it while it was tangled up in some of my sparse arm hair.

After chilling the tiny, 3 millimeter creature in the fridge for a few minutes, I dumped it out into a casserole dish to photograph it. Well, it was apparently completely unaffected by the cold and flew off after I fired off only a couple of legible shots. About 30-45 seconds later, from out of nowhere, it landed on my chest. I guess it pays to be a mammal to keep these flies under some degree of control. A couple of days later, I found the fly had self-broken its wings, such that they were mere stubs. Despite that, the insect was still highly mobile and most of my shots were as blurry as when it had flight capability.

The next encounter was at a blacklight set up to attract moths in Cheyenne Mountain State Park on the night of June 4. I routinely scrutinize the most minute of creatures in the event they may be of interest, and much to my surprise there was another "ked." It, too, was fully winged but, perhaps mesmerized by the ultraviolet light, sat motionless and allowed me to take multiple images....most of which are still not optimal because the blame bug is so miniscule.

Want to find your own louse flies? You might volunteer to go hunting game mammals and birds with your friends to get a chance at shaking one loose. Otherwise, good luck. These insects are common, but so seldom stray from hosts that it is sheer serendipity to stumble across one. More than likely, the fly will find you.

Strange Behavior Explained (Sort of)

The other day (Monday, June 6 to be exact) I was exploring Adams Open Space behind the public library in Fountain, Colorado with my wife. I happened to notice a small ichneumon wasp on the underside of a leaf and snapped a couple of images. This was the best one, and I was shocked to see a cluster of eggs beneath the wasp's abdomen. What was going on?

It had been my previous understanding that female ichneumon wasps deposited their eggs on or in their host, as they are parasitic on other kinds of insects (and spiders in some cases). Why was this one laying her eggs in a mass on the surface of foliage?

I posted the picture and posed that question to a Facebook group of world authorities on Hymenoptera, the order of insects to which ichneumons belong. The next morning I got an answer, courtesy of one Sasha Varga, a doctoral student in the Ukraine. First, he offered the genus identification of Polyblastus. That was surprise enough because the overwhelming majority of ichneumon wasps can barely be identified to subfamily from images alone. Thank you, Sasha!

Varga went on to explain that "as I understand, egg remains on the ovipositor after unsuccessful oviposition, but only one and why Polyblastus accumulates several eggs I really don't know." I was simply impressed with Sasha's command of the English language at this point. Ok, so now I at least have some clarified information I can run with.

Wait, Jitte Groothuis added a link to an article that might shed a little additional light. Jitte is likewise a PhD student, at Wageningen University in the Netherlands. Wow, this little observation of mine is circling the globe....

The article cited is entitled "Eggs and Egg Loads of Field-collected Ctenoplematinae (Hymenoptera: Ichneumonidae): Evidence for Phylogenetic Constraints and Life-History Trade-Offs." It is authored by Heather M. Cummins, Robert A. Wharton, and Aubrey M. Colvin, all of Texas A & M University. It was published in 2011 in the Annals of the Entomological Society of America, vol. 104, no. 3, pages 465-475. This sounds like it is over my head, too, so let's investigate together.

Apparently, an understanding of this paper hinges on an understanding of the differences in life histories between various groups of ichneumon wasps. Some ichneumons are "idiobionts," which means that further development of the host insect is arrested at the time it is parasitized by the idiobiont. Typically, a pupa stage is targeted, but sometimes a larva host, and the ichneumon wasp larva is invariably an external parasite. Idiobiont ichneumon wasps are also much more likely to be "generalists" with a wider range of host insects they can expolit.

Other ichneumon wasps are "koinobionts," meaning that the host organism continues its development at least until the wasp larva completes its development, at which time the host often (usually?) dies. Koinobionts can be either external or internal parasites, though the wasp larva is usually attached to the host, never straying to another host or otherwise moving freely away from the host. Koinobionts are also much more likely to be specialized on a narrow range of host species, in contrast to the generalist idiobionts.

Our Polyblastus here is a koinobiont. In its larval stage it is an ectoparasite (external parasite) of sawfly larvae. The adult wasp emerges from the cocoon spun by the host sawfly larva. This makes sense. We even found a female Elm Sawfly, Cimbex americana at the same location on the same day, so we know potential hosts are present.

According to the abstract of the article, the egg loads of female koinobionts like our Polyblastus are "significantly larger" than the egg loads of idiobiont ichneumons, though the eggs themselves are smaller in koinobionts. Unfortunately, an abstract is all I could find online. I will amend this post should I secure a copy of the entire paper. Maybe having so many eggs, our female wasp is forced to carry some of them externally? How does she keep from losing some simply in the course of searching for a host? How does she manage to attach her eggs to the host one at a time (assuming she deposits ova singly)?

Once again, an innocent observation turns into a convoluted and puzzling mystery. That is exactly what I love about entomology, though. It is a science that keeps you in a constant state of awe, forces you to think imaginatively, and challenges your research skills to the maximum.

Sources: Carlson, Bob. 2010. "Tribe Tryphonini," Bugguide.net.
Cummins, Heather M., Robert A. Wharton, and Aubrey M. Colvin. 2011. "Eggs and Egg Loads of Field-collected Ctenoplematinae (Hymenoptera: Ichneumonidae): Evidence for Phylogenetic Constraints and Life-History Trade-Offs," Ann. Entomol. Soc. Am. 104(3): 465-475.
Goulet, Henri and John T. Huber, eds. 1993. Hymenoptera of the World: An identification guide to families. Ottawa, Ontario: Agriculture Canada. 668 pp.