The Wasps and the Fly

You literally don't have to do anything but step out the door to observe fascinating phenomena in the world of insects. I did just that on August 9th, and found myself watching peculiar behavior between a nest of European Paper Wasps, Polistes dominula, and an unidentified fly.

The paper wasp nest has been on the back of our fence gate for months, now. The occupants are amazingly tolerant, even as we come and go. They may get a bit disoriented if we leave the gate open for a lengthy period, but otherwise they are innocuous and we let them be. Imagine my surprise when the thing that has agitated them most was what appeared to be a house fly.

Upon closer examination, the fly had slightly different markings than a house fly, was spinier on the abdomen, and had perhaps longer legs. It walked a lot, nervously, and it was difficult to even get an image of it. Finally, it stopped walking and started, well, stalking towards the wasp nest. One wasp took notice and adopted a very alert posture. Suddenly, the fly flew off its perch and looped around the wasp nest at dizzying speed. It was so quick I was not sure what I was seeing.

The aftermath of the fly's reconnaissance mission was even more dramatic. The one wasp that had seen the fly in the first place suddenly began running frantically and erratically all over the comb, for probably at least ninety seconds. The fly was long gone, but I was suspecting that maybe it had laid an egg and that was the object of the wasp's energetic searching behavior.

Still puzzled by the fly's identity, I took to the internet for the most likely suspects: a tachinid fly, family Tachinidae; or a parasitic sarcophagid (Sarcophagidae). I found a tachinid that looked promising, but viewing images of the species it became readily apparent this was not the right one. Sarcophagids came up empty as well. Furthermore, I have witnessed paper wasps eating sarcophagids, not falling victim to them. Next I looked to my library and found a potential match in a European field guide, of all things. Eustalomyia festiva, a member of the diverse but obscure family Anthomyiidae, looked good. According to the text, it "Breeds in [the] bodies of flies stored by solitary wasps." Ok, but paper wasps are social....

I posted the images shown here on the help group "Hymenopterists Forum" on Facebook, and got this reply from Rui Andrade:

"It looks like Eustalomyia (Anthomyiidae). The larvae are kleptoparasites of wasps."

This makes sense to a degree, but social wasps do not store their prey for later consumption by their larval offspring. They feed masticated prey directly to the larvae. There is therefore no opportunity for a fly larva to develop in a social wasp nest under those circumstances, as a kleptoparasite feeding on prey intended for the host's offspring. The only alternative I can fathom is that the fly is parasitic on the wasp larvae themselves. Cursory review of the literature does not inform my opinion, as they all stubbornly state that solitary wasps are the victims of Eustalomyia. The wasps are not going to let me peer into each cell to see if there is something other than a wasp egg or larva inside, either.

Perhaps this one individual fly was just confused as to the proper host. Maybe it was initially attracted to the bee block ("bee condo") hanging up on another part of the fence, where we have indeed had solitary wasps nesting. This year the bee condo has been devoid of activity for the most part, so maybe scaring the paper wasps was an amusement borne of frustration for this fly. We may never know.

Sources: Chinery, Michael. 2012. Insects of Britain and Western Europe. A Domino Guide. London: Bloomsbury Publishing. 320 pp.
McGavin, George C. 1992. The Pocket Guide to Insects of the Northern Hemisphere. London: Parkgate Books, Ltd. 208 pp.

In-Kind Donations: Thank You

This blog may be written by me, but it is a team effort that keeps it going. For example, were it not for the recent donation of a new camera, I would not have the ability to take images with a flash. It is thanks to such in-kind donations, as well as monetary gifts through my Paypal donation button, that I can continue to provide content here without going broke.

Debbie Barnes-Shankster, a truly professional nature photographer, had a "spare" Canon PowerShot SX50 that she was not using, and so graciously turned it over to me. I had exhausted the lifespan of the pop-up flash on my other two cameras, so was not able to take images in low light, let alone at night at a moth sheet. I am very grateful to Debbie for the rescue.

Besides equipment, I periodically receive review copies of books, which reminds me that I am behind in my reading more than I would like to admit. I get to keep the books, which then provide additional, newer sources of research for later blog posts. Many of these books are well beyond my budget, and so I am very thankful for those as well.

Sometimes, I have the ammunition to write a post, but not the images to illustrate it. I often solicit photographers for permission to use theirs, and I have rarely been turned down. I don't believe I have ever been turned away, in fact. I am not what I would call even an amateur photographer, but I do assign value to my own work, and am highly respectful of the effort and expense it takes others to get quality images. At some point I would like to be able to compensate photographers for the privilege of using their work here.

Meanwhile, I have huge investments looming on the horizon. I need another vehicle after a minor accident totaled our old Saturn. My HP desktop computer is ancient by today's standards, probably at least seven years old and nearing capacity thanks to photos and videos eating up memory. Before I can even dream of replacing either of those, I still owe a substantial sum to a publisher for a contract that we mutually decided to dissolve, after I had received the advance.

I rarely go begging to anyone for donations, and I am not going to do that now. My goal with this post is to communicate my deep appreciation for what I already receive, and to let you know that your monetary contributions are well spent in feeding the content at this blog.

All my readers are entitled to request blog topics, and I will do my best to honor those queries. We have a global community of participants here at Bug Eric, one that is growing all the time. I value each and every one of you, and thank you whole-heartedly for your patronage.

Wasp Wednesday: Another Puzzler

A good many people mistake me for an expert who knows everything about every insect known to man, but I am not. Thankfully, there are entomologists like Doug Yanega who do seem to know everything, but he would be the first to deny that claim as well. Still, I have learned more from him than I can possibly recount. Case in point a wasp that had me scratching my head over the weekend.

This all started out innocently enough. I was down at Chico Basin Ranch, a sprawling 88,000 acre cattle ranch that straddles the El Paso and Pueblo County line on the high plains, looking for grasshoppers with several other members of the Mile High Bug Club and the general public. At our first stop out on the heavily-grazed shortgrass prairie, one of the first insects that got my attention was a small, maybe 20 millimeter-long, slender black-and-red wasp that was running erratically between patches of grass.

I had it pegged as either a thread-waisted wasp in the family Sphecidae, or a spider wasp in the family Pompilidae, both of which behave in this manner as they search for potential prey. I did not have the camera set for speeding Hymenoptera, so the images are a bit blurry. Now I am wishing I had spent more time with this creature, but hindsight is twenty-twenty. I do not recall the wasp ever flying, but I figured a close approach might send it fleeing permanently.

Back at home, reviewing the magnified images on my computer, I quickly decided I had no clue at all as to what I was looking at. It seemed to be a fusion of the two potential suspects I had surmised initially. So, off to the "Hymenopterists Forum" on Facebook I went. Posting the images there got me several "likes," but no one ventured an identification. Enter Doug Yanega, a good friend and colleague from the University of California at Riverside. He is always willing to help others online and in person, and the university's collection is so well organized that he can use it as a reference for cases like mine.

"I just recalled the other name I was thinking of: Pterombrus rufiventris (now in Thynnidae). I can't find any photos of it online, but I caught one in Kansas once and it had me stumped for a while," wrote Doug. Well, nice to know I'm not the only one who has been baffled by this species. Doug went on to add "Just checked our collection, this is Pterombrus rufiventris, and it attacks cicindeline larvae. Very rare but widely distributed. No photos in BugGuide."

It is no wonder that I did not recognize it, because the most common thynnid wasps are in the genus Myzinum, and they look nothing like this. See my blog post on those here.

The Large Grassland Tiger Beetle, Cicindela obsoleta is one known host for this wasp.

Cicindelines are known commonly as tiger beetles, colorful and active predators in their own right. The larval stage typically lives in a vertical burrow with a diameter just barely large enough to accommodate the grub. The larva has a flattened head that is held flush with the top of the burrow, the better to see, lunge after, and seize any unsuspecting insect that happens by. The victim is then dragged into the burrow to be consumed. A wasp has to have a lot of bravery to take on one of these voracious beasts, armed as they are with large and powerful jaws. True, the wasp does have her stinger, and I can only imagine how deftly she must wield it to be successful.

According to field observations by others, the wasp crawls down the burrow of the tiger beetle larva and stings it repeatedly under the head or thorax, before depositing an egg on the grub's abdomen. The mother wasp then plugs the burrow with a solid, compacted layer of soil, and then fills in the remainder of the burrow above the plug with loose soil particles. Her egg hatches in about 3 days, and the wasp grub that emerges grows by feeding on the tiger beetle larva for almost 9 days. The mature wasp larva then detaches from the now-deceased host and spins a cocoon in the burrow of the host. There it overwinters, emerging the following summer with the monsoon rains of July.

Indeed, this year Colorado has seen extraordinarily heavy precipitation from severe storms. Timing is everything, and I consider myself lucky to have crossed paths with this rare insect. These are perhaps the first images online of the species. Keep your eyes out for this, the western subspecies P. rufiventris hyalinatus, and the eastern subspecies P. r. rufiventris, from southern California to Texas, and on to Georgia and Virginia.

Sources: Knisley, C. Barry, Darren L. Reeves, and Gregory T. Stephens. 1989. "Behavior and Development of the Wasp Pterombrus rufiventris hyalinatus Krombein (Hymenoptera: Tiphiidae), a Parasite of Larval Tiger Beetles (Coleoptera: Cicindelidae)," Proc. Entomol. Soc. Wash. 91(2): pp. 179-184.
Krombein, Karl V., et al. 1979. Catalog of Hymenoptera in America North of Mexico Volume 2. Washington, DC: Smithsonian Institution Press. 1199-2209.

Why I Don't Give Pest Control Advice

Casual visitors to my blog often seek pest control advice in the comments of posts about insects or spiders they themselves have encountered. There are several reasons why I do not discuss pest control, and it is probably high time I outlined them here.

Liability

Commercial insecticide manufacturers and pest control companies ("exterminators") have entire teams of lawyers to prevent, fight, and settle litigation filed against them when customers misuse or fail to fully understand their products or services. Indeed, the public regularly misapplies over-the-counter products resulting in poisoning of family members or pets or, in the case of foggers ("bug bombs"), fail to extinguish a pilot light and set fire to their property or blow their house up. Besides the injuries and/or damage, misapplication of insecticides is a federal offense.

Meanwhile, there are also the pest control equivalents of snake oil salesmen who promise "organic" controls that are ineffective at best, or outright fraudulent at worst. Products such as ultrasonic repellent devices are known by entomologists to be useless; and "bug zappers" kill far more beneficial insects with next to no impact on mosquitoes.

As a writer who is essentially a sole proprietor volunteering factual information, there is no way I can possibly absorb the financial impact of a lawsuit should someone misinterpret pest control advice or product endorsement.

My mission is Teaching Tolerance of Arthropods

Those who follow this blog know and understand that the entire purpose of the content here is to educate the public and foster an appreciation and tolerance of insects, spiders, and other arthropods. Focusing only on the negative impacts some species sometimes have on humanity would not accomplish that goal. There is enough misinformation and media sensationalism already. It is a tide I can barely swim against. Some people I will never "convert" or even reach, but I like the idea that I can provide ammunition for others to argue the overwhelming benefits of arthropod diversity and healthy ecosystems, be they natural, agricultural, or urban or suburban.

"I got you a gig at Al's Produce and a world tour with Union Carbide"

I Do Preach Prevention

Those rare posts I devote to household and garden pests usually include tips for preventing pest issues. Pests are largely our own creation. We provide them with their favorite foods. We give them shelter. We collectively import them accidentally or intentionally from other parts of the world in commerce, including nursery stock (plants). We apply pesticides to which they develop resistance. We compromise native habitats and ecosystems through use of non-native plants in landscaping, overuse of herbicides that destroy food plants for beneficial insects, and insist on large areas of sterile lawns.

It is only by altering our own mindset, or at least our behaviors, that we can coexist with other organisms, and discourage visits by species that can cause us harm. Prevention is the act of executing those proactive, low-cost or no-cost strategies, in contrast to being reactive, at a high financial and emotional cost, when a population of insects or arachnids gets out of control.

There Are Other Sources for Pest Control Information

The smart consumer looks to unbiased sources of information for pest control, as they do when purchasing any product or service. Online, you should be consulting ".edu" websites that originate at colleges and universities. They have no stake in the stock of a company, and because they are educational institutions, they are mandated to provide information to the public. The Cooperative Extension Service has long been a leader in urban and agricultural pest management, but has fallen on hard times with funding cutbacks from the government. Still, pursue that option. There is usually an extension agent office located in whatever town serves as your county seat.

Remember the public health department is a valuable resource for control of insects that affect public health, such as mosquitoes, other biting insects, filth flies, and cockroaches. Contact them, and take them a specimen of the organism that is problematic for you.

Pest control technicians are the last people you should trust for making an accurate identification of a troublesome insect. I cut them a little slack because their first, and often only, priority is to comply with state and federal regulations in chemical pesticide application. Few technicians are properly schooled in entomology, and that is a disservice to the consumer.

#$%!* termites!

Social media outlets vary widely (and wildly) in terms of legitimate, educated advice and identification of insects and spiders. Some Facebook groups are better moderated than others.

Use the "Forum" Tab on This Page

You are certainly welcome to click on the "forum" tab at the top of this page and ask questions and upload images of your mystery "bugs." I'll do the best I can to identify your creature, and direct you to additional informative resources. Thank you.