House Flies

Happy “Fly Day Friday,” dear reader, and Happy Holidays, too. I hope you don’t have to share the leftovers with household pests, but I thought you might enjoy learning a little about one of the more common “guests” you could be entertaining at almost any time of year: The House Fly, Musca domestica, in the family Muscidae.

Naturally, house flies are most abundant during the warmer months, and you are unlikely to encounter them in the dead of winter unless you live in our southerly latitudes, and/or in a rural area. In fact, the House Fly is more common around farms, ranches, zoos, and stockyards than anywhere else. Why? A favorite food of House Fly larvae is horse manure.

Here in Colorado Springs, where your neighbor up the street might have a pony, we see more house flies than you might expect for an urban area. We don’t see them now, though, despite what some people may claim. The problem is one of mistaken identity. Several other flies are commonly mistaken for the House Fly.

House flies are not very large, measuring a mere 6-7 millimeters in body length. They are overall dull gray with beige or yellowish flanks (the sides of the abdomen). They have white faces with large, dark eyes. Those eyes converge and nearly meet at the top of the head in male house flies, while the eyes are farther separated in females.

House flies are smaller than most other flies they can be confused with. Many kinds of blow flies in the family Calliphoridae overwinter as adults and can be seen on sunny winter days basking on the south-facing exterior walls of buildings. Calliphorids are robust, and often metallic to some degree, especially on the abdomen.

Blow Fly

Flesh flies of the family Sarcophagidae sport bold, black stripes down the top of the thorax. They also have scarlet eyes and “tails,” the tip of the abdomen being red, most noticeably so in males. Both flesh flies and blow flies are usually more abundant in urban areas than house flies are.

Flesh Fly

Heleomyzid flies are about the same size as house flies, but appear more slender with longer, narrower wings. These “sun flies” do appear in late autumn and early spring, sometimes indoors. Note the row of setae (hair-like spines) on the leading edge of the wing that distinguishes heleomyzids from similar flies.

Heleomyzid Fly

House flies groom fastidiously, for keeping clean allows them to more quickly notice and evade the swatter. Watch one and be amazed at the gymnastic maneuvers it goes through to shine its wings and polish its eyes. The devious personality we assign to these pests is no doubt heightened when they rub their front feet together like a vintage movie villain wrings his hands while generating a fiendish plot.

Despite their personal hygiene, there is no question that house flies are mechanical vectors of many pathogens that cause illnesses as mild as diarrhea or as serious as typhoid fever. It should be noted that the House Fly has mostly been implicated in the transmission of diseases. Still, house flies don’t discriminate between something edible and something that has already been eaten and passed out the other end.

House flies pass through complete metamorphosis and can go from egg to adult in as little as two weeks time under optimal conditions. There can be ten or twelve generations annually in temperate climates. The female lays batches of 75-150 eggs in a three or four day period, depositing the ova in a food source. Horse manure may be a preferred food, but any decaying organic matter suffices for breeding these insects. A maggot molts only twice after hatching from the egg, the third molt resulting in the pupal stage. The pupa is encased in a capsule-like shell that is the last larval “skin.”

Proper sanitation is the best way to keep house flies at bay, but some people swear by the simple technique of hanging a clear Ziplock baggie, half-filled with water, on the outside of a screen door. Scientists have largely dismissed this trick as hogwash, but experiments haven’t established conclusive proof one way or the other (Mikkelson and Mikkelson, 2013).

House flies are found pretty much the world over, but apparently the species originated in the steppe regions of interior central Asia. Livestock traffic and other commerce no doubt spread the fly far and wide long ago.

Oh, back to the flyswatter. Wonder why you are seldom successful? Flies, like many insects, perceive motion much better than people. It is said that a House Fly would see a motion picture as a series of still images. Your best technique for nailing one of these pesky critters is to sl-o-o-o-wly lower your weapon to within a few inches of the target, then quickly slap it down….Yeah, good luck with that.

Sources: Berenbaum, May R. 1989. Ninety-nine Gnats, Nits, and Nibblers. Urbana, IL: University of Illinois Press. 263 pp.
Sanchez-Arroyo, Hussein, and John L. Capinera. 2008. “Common Name: House Fly,” Featured Creatures, Entomology & Nematology, University of Florida
Mikkelson, Barbara and David P. 2013. ”Fly Bye,” Snopes.com.

Eastern Cicada Killer

Mowing the lawn one August day, Jim noticed saucer-sized piles of soil in the bare patches, with a large hole on the edge of each one. He figured it was the work of rodents until he saw an enormous wasp enter one of the holes dragging another large insect behind it. Jim decided to avoid that part of the yard.

This scenario, and others like it, plays out over much of the eastern United States during the summer, creating mystery, annoyance, or downright hysteria for those finding that the Eastern Cicada Killer, Sphecius speciosus, has taken up residence on their property.
A Community of Killers
Cicada killers are solitary. This means that each female wasp excavates her own nest. Many wasps may burrow in the same area, creating the impression that they are giant, social yellowjackets or hornets. Male cicada killers, while incapable of stinging, will drive off other males, other insects, even birds as they seek mating opportunities with females. They sit on the ground, or foliage, rocks, or other objects that give them a somewhat elevated perch from which to survey their territory. Watch them cock their heads alertly at the passing of other wasps.
The female digs her burrow before she starts hunting. The tunnel extends up to three feet, at a depth of two feet. Individual cells branch off near the end of this shaft. Each “room” will host one of her offspring.

The Eastern Cicada Killer hunts mostly “annual” or “dog-day” cicadas in the genus Tibicen. These large, loud insects are heard in the tops of deciduous trees during July and August. The female wasp flies into the canopy and combs each branch until she bumps into a cicada. She grabs the insect and stings it into paralysis. A “shrieking” cicada is likely being attacked by a cicada killer.
The Cicada Killer Life Cycle
Cicada killers are strong. A wasp may fly directly from the scene of the crime back to her burrow, carrying her prey beneath her. Sometimes the journey is accomplished in stages, gliding from the tree to the ground, up another vertical object to launch another short flight, and so on until she gets home. She has to hurry: birds often harass cicada killers into dropping their prey.
She dives down the entrance to her burrow, hauling her prize to one of the underground cells. One cicada is enough to grow a future male cicada killer, but a baby (larval) female cicada killer needs to eat at least two cicadas, sometimes three. The mother wasp lays a single egg on the last cicada put into a cell. When all cells are filled, she fills the nest entrance and leaves permanently.

Typical cicada used as prey The cicadas are paralyzed, not dead, which prevents them from spoiling until the wasp larva finishes consuming them. The egg hatches in a day or two, and the larva starts feeding. It matures quickly, in an average of ten days. The larva then spins a silken cocoon, incorporating soil particles into the capsule. Inside that covering it turns into a pupa, the externally inactive stage of metamorphosis. Pupae overwinter within their respective cells, the adult wasps chewing their way out the following summer and beginning the cycle anew.
Fueling up
Both male and female cicada killer wasps feed on substances rich in sugars and carbohydrates to fuel their energetic activities. Look for them on flowers where they sip nectar. Also look for them eating oozing, fermenting sap on the trunks of trees. Some of the images shown here depict this behavior. I even gently nudged one of the big female wasps into a better position while I was taking pictures.

Cicada killers are probably the largest, bulkiest wasps you are likely to see east of the Rocky Mountains from Massachusetts and southern Ontario to Florida and Texas. The adult wasps range from 30-40 millimeters in body length, though some females can be up to 50 millimeters (just shy of two inches). No wonder they can seem so intimidating.
Nothing to Fear
Solitary wasps will not sting unless physically molested, or you step on one in bare feet. Male wasps may behave aggressively, but they lack a stinger.

Should you be fortunate enough to have cicada killers in your garden, enjoy watching the drama of their lives. The adult wasps live only 2-6 weeks, so the phenomenon of their nesting is fleeting.
Sources: Holliday, Charles. 2012. “Biology of Cicada Killer Wasps,” Prof. Chuck Holliday’s www Page at Lafayette College.
O’Neill, Kevin M. 2001. Solitary Wasps: Behavior and Natural History. Ithaca, NY: Comstock Publishing Associates (Cornell University Press). 406 pp.
Shapiro, Leo, et al. 2012. “Sphecius speciosus: Eastern Cicada Killer,” Encyclopedia of Life.

"Albino" Bugs

I am frequently presented with descriptions or images of what people assume are “albino” insects. Usually, the specimens are clearly lacking pigment. The mistake is understandable, but there is precious little information widely available to explain what is actually going on. Allow me.

As far as I am aware, there is no such thing as an albino insect, spider, or other arthropod. Aside from some species endemic to caves where there is no sunlight, there are no species permanently devoid of pigment. What people are finding are specimens that have recently molted. In the immediate aftermath of shedding its exoskeleton (“skin”), an insect is generally soft, wet, and white, eventually hardening, drying, and darkening. The newly-minted adult American Cockroach shown above is a typical example. Note the slightly darker individual at bottom that had molted hours earlier.

Molting is known as ecdysis in scientific lexicon. It is a highly complicated process that is governed largely by hormones, and makes possible the astonishing transformations known as metamorphosis.

We came to learn of the complexities of insect development through the diligent work of physiologists that commenced around the early 1920s. Some rather primitive and grotesque experiments by Stefan Kopec in Poland demonstrated that just prior to molting the insect brain sends a signal to the prothoracic gland which in turn produces molting hormones called “ecdysones.”

Ecdysones are actually steroidal hormones. Their levels are elevated suddenly before molting, triggering a cessation of feeding and stimulating gene expression (and/or suppression?) that will apply to the next stage of development.

Many freshly-molted true bugs are pink

The presence of another hormone called “juvenile hormone” means that the next developmental stage will be another larval or nymphal instar. The absence of juvenile hormone (JH) in the haemolymph (insect blood) signals transition to the pupa or adult stage, whichever applies. JH is also important in reproductive biology in the adult male insect, even though its effects are dormant during metamorphosis.

Back to the actual process of molting. Epidermal cells begin manufacturing a new exoskeleton, while at the same time enzymes are liberated into a “molting fluid” that erodes the inner layers of the old cuticle, making those amino acids and sugars available for recycling into the new exoskeleton. Muscle attachments to the old cuticle are actually broken through rhythmic contractions of the insect’s body from back to front.

Cicada molting to adulthood

The old cuticle splits along predetermined ecdysial sutures, kind of like the perforations that allow you to easily open a box. As the insect extricates itself from the old exoskeleton, a waterproofing substance is deposited atop the new cuticle. This material is secreted by dermal glands.

Once the insect is free of the old “skin,” it takes in air to literally inflate itself to a larger size while the new cuticle hardens. This hardening process takes hours if not days, and is called “sclerotization.” This process begins prior to molting in the jaws (and sometimes other body parts like the crochets on the prolegs of caterpillars).

Insect larvae have a thinner, more flexible exoskeleton than nymphs, pupae, and adult insects. Therefore they are often not as densely pigmented. The shed exoskeleton of a larva with chewing mouthparts is often consumed by the insect itself so as to recycle the nutrients and eliminate evidence of its presence to keen-eyed birds and other predators that are alert to such signs of insects.

People who find the shed exoskeletons of insects may think that the ghostly objects are actually living specimens. The durability of shed exoskeletons is indeed astounding. Cicada shells may remain affixed to trees and other vertical objects for months after the adult insect has lived and died. Oh, and those stringy white things protruding from the seam where the insect emerged? Those would be the remains of major tracheae. Yep, even the tracheae of insects is sclerotized.

A shed exoskeleton is called an "exuvia," plural "exuviae"

Considering how vulnerable insects are during, and immediately after, molting, it is amazing how many survive to adulthood. Predators can get them while they are soft and immobile. They can become hopelessly entangled. Yet, here they are, the most successful and abundant of all organisms.

Sources: Hadley, Debbie. 2013. “How Insects Grow – The Molting Process,” About.com.
Mills, Erin. 2011. “In My New Skin,” Beyond Bones blog, Houston Museum of Natural Science
Resh, Vincent H. and Ring T. Cardé (Eds). 2003. Encyclopedia of Insects. San Diego, CA: Academic Press (Elsevier Science). 1266 pp.

The Obscure Bird Grasshopper

The Obscure Bird Grasshopper, Schistocerca obscura, might be better named the conspicuous bird grasshopper, for it is one of the larger and more eye-catching of its kind. An adult male can be 36-45 millimeters in length, while females can reach a whopping 50-65 millimeters (2-2.5 inches). They may startle you by exploding into flight from grasses and shrubs, as they are alert and quick to depart the scene if discovered.

Female

I had the privilege of encountering numerous specimens this fall when my wife and I visited the Prairie Center (Olathe, Kansas), and Leavenworth, in late September. Indeed, all the images here were taken on September 21.

This species is related to the famed Desert Locust, Schistocerca gregaria, that periodically makes headlines for its near apocalyptic swarms in Africa and southern Europe. S. gregaria is the sole Old World representative of the genus. We have ten species in North America, as of the most recent revision of the genus.

The term “locust” correctly applies only to the migratory phase of a few species that are normally solitary. Overcrowding in the nymph stage is what triggers the change. Nymphs literally rub elbows (er, “knees”?) while marching overland, and this constant jostling stimulates hormonal changes that lead to an adult stage that is more streamlined, with proportionately longer wings, than the average member of its species.

Locust swarms number in the millions if not billions, and while the insects themselves are powerful fliers, they also take advantage of storms, riding the winds ahead of fronts. When they settle, almost anything is fair game for their diet, including dead and dying members of their own kind. Most species in the order Orthoptera are, in fact, ominovorous.

Fortunately, The Obscure Bird Grasshopper and its New World relatives are rarely populous enough to be so destructive to agriculture. That is not to say that they do not migrate. They are capable of long distance seasonal migrations that can take them outside of their normal ranges. S. obscura is widespread in the eastern U.S., from Maryland south to Florida and west to Kansas, Texas, and even parts of New Mexico and southeast Arizona (south through most of Mexico). While it has been documented as far north as Pennsylvania and Nebraska, its roots are in the south and those northerly records are mostly a result of seasonal migrations during favorable years.

Male

Several other species in this genus may closely resemble the Obscure Bird Grasshopper, and it is necessary to examine the tip of the male’s abdomen to make a concrete identification. The preferred habitat of this species is open woodlands, which contrasts a little with look-alike species. Adults can be found from July through September, a little earlier and later in the most southerly latitudes.

If you have trouble differentiating all the Schistocerca anyway, take heart. Species and subspecies delineations are still being debated among experts. Just count yourself lucky if you happen upon a population or migration of these stunning insects. They literally don’t come around that often.

Sources: Capinera, John L., Ralph D. Scott, and Thomas J. Walker. 2004. Field Guide to Grasshoppers, Katydids, and Crickets of the United States. Ithaca, NY: Comstock Publishing Associates (Cornell University Press). 249 pp.
DiTerlizzi, Tony, et al. 2011. “Species Schistocerca obscura - Obscure Bird Grasshopper,” Bugguide.net.
Hojun Song. 2004. “Revision of the Alutacea Group of Genus Schistocerca (Orthoptera: Acrididae: Cyrtacanthacridinae),” Ann. Entomol. Soc. Am. 97(3): 420-435.