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WOWBug FAQs
(Frequently Asked Questions)

Q. What are WOWBugs?

Classification: Melittobia digitata Dahms ("Melly-toe-bee-ah dij-it-ah-tah") Order Hymenoptera, Family Eulophidae

WOWBugs are harmless, non-stinging wasps about 1 mm long. In nature, they lay their eggs on the outside of the larvae or pupae of other insects, primarily solitary wasps and bees. Their hosts include a number of different insect species, but they prefer to parasitize mud dauber wasps.

Worldwide, 14 Melittobia species have been described. All have superficially similar behavior. One of these species, Melittobia digitata, has been given the common name, WOWBug. It is slightly larger and easier to use in the classroom than its close relatives.

Q. What can WOWBugs teach my students?

With their rapid life cycles, fascinating behaviors, no-hassle care and strange morphology, WOWBugs are extremely engaging insects with which to elicit student interest and learning.

• WOWBugs are among the best insects to demonstrate complete metamorphosis. Each stage, including the egg, is easily observed. The life cycle is rapid, requiring about 25 days at moderately warm (75-78 degree) temperatures.
• WOWBugs are excellent choices for developmental and introductory genetic studies. The male and female sexes are extremely different, and can be reliably distinguished even as pupae. Females are diploid, but males are haploid. Thus, mated females produce both sexes, but unmated females produce only males.
• WOWBugs excel for behavior studies. Their repertoire is bizarre and reliably elicited. Courtship, aggression, orientation, and responses to pheromones are but a few of the areas in which both scientific studies and classroom activities have been published.

Q. Are WOWBugs practical in the classroom or laboratory?

Emphatically yes! Consider these advantages:

• WOWBugs are simple to maintain under normal room temperature and humidity. They require no special feeding or other care. Females will reliably feed, however, when offered a new host, and they use that nourishment to develop their clutch of eggs.
• WOWBugs are harmless, safe, and cannot sting humans. Although they have wings, they usually do not fly.
• Because one small culture yields 150 - 300 adult insects, WOWBugs beg to be shared. A single culture in a vial or pill bottle will provide enough insects for several classes, or for multiple experimental trials.
• WOWBugs pose no environmental risk, should a few escape. They are native insects that are already widely distributed. When their classroom sojourn is over, we recommend euthanization of the culture by freezing. The genetics of field populations are poorly understood and release of laboratory cultures could have unknown genetic consequences for the local populations.

Q. What curricular materials are available to help me use WOWBugs?

The manual, WOWBUGS: New Life for Life Science, provides background information, photocopyable materials, over 20 detailed activities and many suggestions for further study. This is supplemented by film footage (VHS and DVD) and 35-mm slides,. These materials may be ordered from Riverview Press, 655 RiverviewRoad, Athens, GA 30606 USA. (706-369-0931)

An advanced activity investigating competitive interactions between two different species of parasitic wasps attacking a single host can be downloaded at:

http://tiee.ecoed.net/vol/v2/experiments/wasps/abstract.html

Additional materials published by others are listed in the Bibliography.

Q. Where can I get living WOWBugs?

In nature, Melittobia digitata and other close relatives can be obtained from the nests of mud dauber wasps or other solitary wasps or bees. It's not difficult.

Carolina Biological Supply Company also carries living WOWBug cultures in their catalog. Each culture contains about 100-300 individuals. These can easily be maintained and/or multiplied on any of several different hosts, including blowfly puparia, the host used by Carolina for their cultures.

Q. What should I feed my WOWBugs?

You don't need to feed them anything. However, when you give the female a host, she will sting it and feed on tiny droplets of insect blood (hemolymph) that ooze from the wound. She must do this to develop her eggs.

Scientists used to think that males did not feed at all. However, they have been seen chewing on the bodies of defeated competitors after a battle between males. Sometimes, we have also seen male WOWBugs wounding females during courtship gone wrong, then feeding on them.

Q. Some of my cultures have mold. How can I prevent it next time?

Most mold problems come from one of two sources: using dirty rearing containers or touching the host larva with your fingers.

Never use containers without washing them first, then rinsing them with dilute bleach, alcohol, or a commercial disinfectant.

When transferring a mature mud dauber larva that you want to remove from its cocoon, dump the larva from its cocoon into the rearing container without handling it directly.

If using a blowfly puparium as a host, leave it intact. It does not need to be opened for the WOWBug to attack it.

Interestingly, while mold spores are everywhere, moldy larvae are almost never found inside intact cocoons. It is possible that the cocoon material contains an antibiotic.

Q. I'd like to do the mud dauber nest dissection activity. But won't collecting a lot of nests for my class reduce local mud dauber populations?

You're to be commended for your concern. Of course, you'll want to act responsibly and not collect more nests than you really need. You may decide to have each pair or team of students use only part of a nest. However, remember that because mud daubers prefer to nest in protected places, many nests are hidden from casual view. Even if you collect a great many, there will still be a refuge population.

Because mud dauber wasps and spiders both adapt so easily to building nests on manmade structures, there are probably more mud dauber nests today than there have ever been. Furthermore, realize that most people consider mud dauber nests to be a nuisance, and will knock them down or destroy them. You're only asking that they be contributed to science instead of being put in the trash. Check with the maintenance personnel at public parks and golf courses, for example, for a supply of these nests.

Q. Help! My WOWBugs are dead! What now?

If you just received a new culture and notice a few dead adults in the container, it is likely that the new generation of adult WOWBugs has not yet emerged from the host puparia. Check this by carefully opening one of the host pupal capsules and look for numerous small red-eyed WOWBug pupae. Carolina usually ships WOWBugs at this stage. Adults will start to emerge from all the host capsules within the next week or 10 days, so plan accordingly.

If you’ve let your culture die out or thought it would live longer, don't despair -- just be flexible. While we're the first to encourage you to use living organisms whenever possible, we also want to point out that even dead WOWBugs have classroom uses.

With very little adaptation, your defunct WOWBug culture can be used in three different activities from WOWBugs: New Life for Life Science:

• Form and Function: Insect Anatomy
• Scale and Accuracy: Just How Big Are WOWBugs - Really?
• Population Sex Ratios

Meanwhile, order another culture or collect one yourself. Plan on using your new culture as promptly as you can. As you've learned, WOWBugs may be hardy but they aren't immortal!

Q. How long do adult WOWBugs live?

Because they exist entirely on energy stores they put away during the days when they were larvae, in most circumstances WOWBug adults simply run out of fuel for living within a week or two. In the lab, with periodic access to hosts, one female is said to have lived over 200 days.

Q. Do mud daubers specialize on any one kind of spider?

From the evidence available so far, it seems as though the organ pipe mud dauber (Trypoxylon) preys primarily on just a very few spider species with very similar habits. They are all orb-weavers that make a vertical web, much like the spider in the famous children's story, Charlotte's Web.

The black and yellow mud dauber (Sceliphron) appears to have somewhat wider tastes. It may prey on any of a dozen or so spider species. But this still is being quite choosy. Over 37,000 species of spiders have been named so far, and this number is believed to be only about a quarter of all that are out there!

Q. I ordered a WOWBug culture from Carolina Biological Supply Company, and when it came, it included a couple of adult wasps and a pupa. But even under a microscope I don't see any eggs. Is something wrong?

Your culture is probably just fine. The adult wasps in your culture now are the original egg-layers. Commercially, blowfly puparia are used as WOWBug hosts, and the reason you can't see eggs is because they were laid inside the cocoon-like cover.

Depending somewhat on temperature, your young WOWBugs should have reached the early pupa stage by the time you received them. When they become adults, they will chew their way out of the puparium to freedom.

If you'd like to take a peek for reassurance that your culture is viable, grasp the fly puparium in your fingers and gently(!) pop open one end using your fingernail. Peer inside the open end under a dissecting microscope.

Opening a blowfly puparium before starting a culture will allow you to see all developmental stages, including eggs. However, in the process of opening it, mold may be introduced and the blowfly pupa is sometimes damaged. Thus for commercial cultures or mass-rearing in the laboratory, the puparia are left intact.

Q. If mud dauber wasps are the WOWBug's natural host, how did anyone figure out that they can be reared on blowflies?

Even though the most common hosts of WOWBugs are mud daubers, these aren't the only insects that a WOWBug may encounter inside a nest. Mud daubers are also plagued by other parasites such as velvet ants, cuckoo wasps, tiny mites, and pirate flies.

Once, when we opened a cell in a mud dauber nest, we found it infested with pupae of pirate flies, so we put them in a covered jar to allow the adult flies to emerge. When checked later, the jar contained not flies but hundreds of Melittobia. It was apparent that when the WOWBug invaders found no mud dauber pupa in the cell, they had attacked the pirate fly pupae instead. And obviously they had been very successful at it.

This gave us an idea. We knew that pirate flies and blowflies are relatives. Since we had some blowfly (Sarcophaga) puparia in the laboratory refrigerator, we exposed them to the Melittobia. And, as they say, the rest is history.

As a footnote to this story, we have since discovered that not all Melittobia species can successfully attack blowfly pupae. Fortunately for us, the WOWBug (M. digitata) is one that does. So it has become the standard alternative host used by commercial suppliers like Carolina Biological Supply Company.

Q. My WOWBugs are developing more slowly than I expected. Any tips for speeding them along?

Because insects are cold-blooded, their development can slow down or speed up, according to temperature. For WOWBugs, an optimum temperature seems to be about 80-85º F. At this temperature, development from egg to adult takes 18-21 days.

Some classrooms are more like 65-70º F., and this can slow WOWBug maturation significantly (25-30 days). A heating pad from the local drug store can come to the rescue, but even the lowest temperature may be dangerously warm for this little living creatures.

You'll need to experiment a bit. Try covering the heating pad with a folded terrycloth towel. Then place a piece of corrugated cardboard on top, and rest the WOWBug cultures on the cardboard. An inexpensive thermometer taped to the cardboard with its bulb touching the surface can serve as a monitor.

Different brands of heating pads undoubtedly vary in their temperature setting and the extent of control. If you decide to use this technique, determine the optimal amount of insulation to add before trusting WOWBugs' fate to it.

Q. Can I use WOWBugs to teach genetics to students?

As of now, no mutant strains are available for genetic experimentation, but WOWBugs surely excel for teaching other dimensions of genetics.

For example, sex determination in WOWBugs is not based on X-Y chromosomes. Instead, males always result from unfertilized eggs (parthenogenesis). Females only result when the egg is fertilized. Thus only females have fathers. In WOWBugs: New Life for Life Science, we have developed this into an investigation called "Momma's Boys" (pp. 198-214).

Another unexpected twist for students is that unlike the 50:50 sex ratio in fruit flies or humans, the population sex ratio in WOWBugs is about 95 females to 5 males. This theme is the focus of another investigation, "Population Sex Ratios" (pp. 198-204).

Q. In our Advanced Placement biology classes, we traditionally study fruit fly courtship, but it's a difficult lab for students. Could we use WOWBugs instead?

Yes, a number of AP teachers have done so quite successfully. Detailed instructions for conducting a laboratory session on experimental observations of Melittobia courtship are available (see Matthews and Matthews 2003 and Guinan et al. 2000 in the bibliography).

Two closely related activities in WOWBugs: New Life for Life Science also help students tie courtship into the bigger picture of animal biology. They are "Courtship Communication (pp. 43-51) and "Darwinian Selection" (pp. 224-228).

Q. When making a new culture, do I need to break open the blowfly puparium or mud dauber cocoon, or will WOWBugs go through the shell to lay their eggs?

The call is yours. We originally thought that the crispy covering of these hosts should be opened, but we have since confirmed that this is not really necessary for successful parasitism. You might want to do it for other reasons, though.

We know that when a female WOWBug is given a blowfly host, she pierces the pupa shell with her tiny stinger. After drinking some of the host's body fluids and maturing her eggs, she deposits them directly on the outside of the immature fly's body inside the puparium. Blowfly pupae are easy for her to reach. They fit tightly inside the puparium, with no space separating the host body from its outer covering.

With mud dauber larvae left in the cocoon, it appears that the female WOWBugs must first chew a small hole to gain access to the host. Immature mud daubers are quite loosely contained in their cocoon, and it appears as though the empty space in the mud dauber cocoon is too large to permit the wasp's short ovipositor to reach the host's body.

Because of these biological differences, you can easily open a mud dauber cocoon and shake out the mature larva into a sterile container to readily observe all stages of the WOWBug life cycle. To do so with a blowfly larva is all but impossible.

However, carefully popping open one end of a blowfly puparium does give one a chance to peek inside and make sure the host is fresh and viable (a particular problem with a certain proportion of these).

Q. I've seen materials describing WOWBugs as "new insects." Are they the product of some sort of genetic engineering? I don't want to accidentally release mutant "killer bugs" into the world!

Rest assured. WOWBugs have been around a long time, and pose no threat to anyone other than their natural hosts. They are "new" only in their use for biology laboratory instruction.

Q. I recently saw some living WOWBugs for the first time, and they seemed awfully small. Will they be any bigger when they grow up?

Once a WOWBug is an adult, it is as big as it will get. Insects have an "outside skeleton" that forms a shell around their soft insides. The only way they could grow as adults would be to shed, or molt, this exoskeleton. Molting is common while insects are growing up, but almost never occurs after insects are adults.

Adjusting to their size is really a matter of adjusting one's perspective. In the first place, Melittobia wasps are almost exactly the same size as Drosophila fruit flies, albeit a bit more slender. In the second place, over three-quarters of all insect species are WOWBug size or even smaller!

The small size of WOWBugs actually works to their advantage, education-wise. They fit easily in the classroom. One doesn't need any large, bulky, expensive laboratory equipment to maintain or study them. Finally, they send an excellent message to students. As one excitedly told us, "I never knew anything so little could be so complicated -- and so cool!"