Month: November 2019

Pumpkin eaters: Fruit flies, Drosophilidae

What has bright vermilion eyes, two wings, and an extraordinary fondness for over-ripe fruit?

What has bright vermilion eyes, two wings, and an extraordinary fondness for over-ripe fruit?

With Halloween a quickly fading memory, I visited my Jack O’ Lanterns one last time before their final journey to the compost heap. While lamenting the passing of my pumpkins, I was delighted to see dozens of tiny winged workers fully engaged in the decomposition process. Flies are important recyclers of dead plants and animals. They provide a vital ecological service by unlocking nutrients tied up in complex molecules and returning them to food webs. In this episode we meet the fruit fly, a master transformer of plant material. The common name fruit fly is often used to describe small ( ~ 3 mm) flies with bright red eyes in the family Drosophilidae (a.k.a. vinegar or pumice flies). Larger flies sporting spotted or banded wings in the family Tephritidae also go by the name fruit fly by virtue of their appetite for fruit and other parts of plants. Details of the former will be investigated today and strange dealings of the latter await another episode.

In autumn I regularly receive questions about hordes of tiny fruit flies buzzing around fruit bowls, kitchen sinks, and counter tops. They seem to appear from nowhere and lend credence to Aristotle’s notion that living organisms like tiny flies can originate spontaneously from non-living or putrefying things. Now famous experiments by Francesco Redi and Lazzaro Spallanzani pretty much disproved Aristotle’s theory of spontaneous generation, but the appearance of hordes of tiny flies remains vexing even for bug geeks.

To help untangle this mystery, consider the change of seasons.  Autumn in many parts of the country is characterized by damp cool weather by virtue of incessant weekly showers. These moist conditions are nearly ideal for decomposing tons of leaves, fruits, and other vegetable matter, the accumulated bounty of Mother Nature’s efforts during spring, summer, and autumn. This week of Thanksgiving my compost pile is a writhing mass of invertebrates intent on converting vegetable protein into animal biomass as quickly as possible. On warm days a cloud of fruit flies hovers over my compost pile and some of these winged raiders undoubtedly infiltrate my home when the door opens. Like many kitchens, mine is home to a bowl of fruit that occasionally contains one item gone a little squidgy. Yeasty odors of acetic acid and ethanol emanating from an over-ripe banana serve as powerful attractants for fruit flies. After arriving at the banana, the female fruit fly deposits eggs. Each gal lays roughly 500 eggs during the course of her life time. Small translucent larvae hatch from the eggs. They glide through the overripe fruit slurping-up nutritious fermenting fluids as they develop and grow. When ambient temperatures are warm, fruit flies can complete a generation in less than two weeks. With their capacity for reproduction, populations around the fruit bowl can explode seemingly overnight.

While adult fruit flies feed on the surface of my pumpkins, taking special care to groom antennae and legs, their offspring are busy dining inside. Watch how the larva uses darkly colored mouth hooks to propel itself forward by grasping the substrate and pulling itself along. Ah, but once it finds just the right juicy spot it stops and slurps the nutritious tissues of decomposing pumpkin flesh.  

Fruit flies can also enter your home as stowaways when you purchase overripe fruits or vegetables from the market. These goods may arrive preloaded with a complement of eggs or tiny larvae. To reduce chances of bringing home an infestation, inspect your produce carefully and wash fruits and vegetables. If fruit is unrefrigerated and displayed in a bowl, check it out regularly and toss over-the-hill items before they generate flies. Fruit flies can also breed in sink or floor drains, garbage pails, or recycling containers in homes, restaurants, and offices where decomposing organic material accumulates. Inspect these areas regularly, clean up spills, and disinfect surfaces.

Yeasty odors of fermenting fruit and wine vinegar lure scores of fruit flies and one fungus gnat to their death.

Yeasty odors of fermenting fruit and wine vinegar lure scores of fruit flies and one fungus gnat to their death.

Fruit flies are more than just an indoor nuisance. Several species are important pests of agricultural crops. The spotted wing drosophila, Drosophila suzuki, first detected in the US in 2008 in California, has now spread from coast to coast and border to border. It is a major pest of strawberries, blueberries, raspberries, black berries, and cherries. Crop losses in the United States alone are estimated to exceed hundreds of millions of dollars annually.  For the cloud of fruit flies wafting around your home, consider building a vinegar trap to catch and kill these noisome rascals.  Traps can be purchased commercially and several trap designs are available on the internet. My vinegar trap consists of an 8 oz clear plastic tumbler filled with 4 oz of wine vinegar and a few drops of dish detergent. Within 24 hours of placing the trap on the counter, more than 100 fruit flies were lured to their death. Stealing a line from Robert Armstrong of King Kong fame (RKO, 1933) “Oh no, it wasn’t the banana that killed the beast. It was the fragrant odor of yeast.”

Hope you enjoy your pumpkin pie this Thanksgiving. Have a happy one!

References

We thank Liz and her buggy bananas for providing the inspiration for this episode. The interesting references “Trapping spotted wing drosophila, Drosophila suzukii (Matsumura) (Diptera: Drosophilidae), with combinations of vinegar and wine, and acetic acid and ethanol” by P. J. Landolt, T. Adams, and H. Rogg,  “Spotted Wing Drosophila: Potential Economic Impact of Newly Established Pest by M. P. Bolda, R. Goodhue, and F.  Zalom, and “Flies, gnats, and midges” by W. A. Kolbe in “The Handbook of Pest Control” were used in preparing this Bug of the Week.

This post appeared first on Bug of the Week

Bug in the bathtub? Nah, house centipede, Scutigera coleoptrata

Strangely delicate and beautiful, but a bit creepy at the same time, house centipedes are common home invaders around the globe.

Strangely delicate and beautiful, but a bit creepy at the same time, house centipedes are common home invaders around the globe.

A couple of weeks ago, a Bug of the Week viewer messaged me about a fast moving, many-legged creature darting across the floor. Early one morning last week I had a similar surprise when I stepped into the shower and was greeted by a magnificent house centipede scuttling around the tub. In previous episodes of Bug of the Week we met other home invaders that somehow wind up in the bathtub, like camel crickets and wolf spiders. The house centipede is yet another creature that evolved in a foreign land and now claims the US as one of its homes. Originally found in the Mediterranean region, it now occupies most of Europe, parts of Asia and Africa, and lands in Central and South America, as well as North America.

‘Centipede’ is a bit of a misnomer. They don’t really have 100 legs, but more like about 30.

‘Centipede’ is a bit of a misnomer. They don’t really have 100 legs, but more like about 30.

Steve Jacobs, an extension specialist at Penn State, related a fascinating story about the house centipede first published by one of the forefathers of entomology in the US, C. L. Marlatt, in 1902. Regarding the house centipede, Marlatt said, “It may often be seen darting across floors with very great speed, occasionally stopping suddenly and remaining absolutely motionless, presently to resume its rapid movements, often darting directly at inmates of the house, particularly women, evidently with a desire to conceal itself beneath their dresses, and thus creating much consternation.”  Ladies, nowadays it’s a good thing workout leggings are in vogue.

In the natural world, house centipedes thrive in moist, cool places and can be discovered on the soil beneath rocks, logs, and fallen leaves. Once inside a home they gravitate to similar locations: man-caves in the basement, laundry rooms, and bathrooms. So, how do they wind up in the bathtub? Well, contrary to popular belief they do not swim up through the drain. This trick is mostly practiced by mammals like rats, able to hold their breath long enough to swim through the water-filled trap in a drain pipe. Centipedes and other creatures found in a tub usually were seeking a tasty insect or spider for a midnight snack on the rim of the tub, slid into the porcelain vessel, and could not scale the slippery walls to escape. Unlike their other many-legged relatives millipedes, that eat vegetation, centipedes are hunters and eat meat. You may recall the stone centipede we met in a previous episode and remember its powerful poison claw that came with the warning of “do not handle” lest you risk a nasty venomous bite. Well, the house centipede is also equipped with a similar, much smaller appendage but bites are rare and, according to several accounts, quite mild.

What a way to start the day – a centipede in the bathtub!

If you encounter a centipede in the tub, please avoid the urge to flush it down the toilet. This is a needless waste of water. Here’s what I do. After discovering a house centipede in the tub, I capture it in a water glass, transport to the backyard, and release it so it can hunt soil-inhabiting garden pests – a win-win for everyone except maybe the garden pests.

Acknowledgements

Bug of the Week thanks an anonymous viewer for inspiring this episode. “House Centipede” by Steve Jacobs provided the technical information. Please check out his great fact sheet at this site:  https://ento.psu.edu/extension/factsheets/pdf/HouseCentipedes2.pdf

Bug in the Bathtub? first appeared on Bug of the Week

Getting by on five – can losing a leg save a life? Leaffooted bugs, Leptoglossus and Diactor, field and camel crickets, Gryllus and Diestrammena

  A fantastic tropical flag-footed bug shows off his remaining hind leg.

A fantastic tropical flag-footed bug shows off his remaining hind leg.

  Leaffooted bugs here in the DMV sport impressive flags on their hind legs.

Leaffooted bugs here in the DMV sport impressive flags on their hind legs.

Last week we met leaffooted bugs being attacked by parasitic tachinid flies. One of the featured creatures in this episode was a five-legged bug limping along in a feeble attempt to escape a nosy camera. Two questions surfaced regarding the five-legged bug in last week’s episode. First, what in the world are those fantastic leaf-like structures on the hind legs for anyway? Second, how did the unfortunate bug lose its leg in the first place? 

Dropping a hind leg on the bathroom floor while avoiding capture was enough to make the paparazzi stop to snap a picture.

Dropping a hind leg on the bathroom floor while avoiding capture was enough to make the paparazzi stop to snap a picture.

This is not the first time we’ve met an insect missing a hind leg. Some of you may recall the episode entitled “Five-legged cricket in the bathtub” where we discovered that quite a few animals may discard an appendage, often a leg or a tail, when attacked by a predator. The strange behavior of discarding an appendage is not uncommon for many insects such as crickets, walking sticks, and yes, leaffooted bugs. A special muscle allows a leg or antenna to snap off at the insect’s will under the right circumstances. This phenomenon, known as autotomy, allows the insect to lose a leg and save its life by distracting a hungry predator. When the predator stops to examine or eat the severed limb, the bug makes its getaway. In some cases, the insect regenerates the missing part.

What message does the flag on the hind tibia of Diactor convey to a would-be predator?

What message does the flag on the hind tibia of Diactor convey to a would-be predator?

In addition to insects, reptiles and mammals use this clever ploy. Some male relatives of the leaffooted bugs we visit today have powerful, enlarged hind legs used to battle other males for territories and access to females. Autotomy in these species comes with a cost to successful reproduction. Apparently gimpy guys are less likely to hold territories and win affections of desirable female bugs. The greatly expanded and highly apparent hind legs of Leptoglossus and the beautiful tropical flag-footed bug, Diactor, likely serve another purpose. One look at the amazing hind leg of the Diactor is certainly enough to attract the attention not only of entomologists but also the eyes of would-be predators. By directing a predator’s attack away from vital organs and body parts, these bugs may lose a leg and prevent the loss of a much more vital body part. For leaffooted bugs, crickets, and many other insects, losing a leg is much better than losing one’s life.  

Five legs propel a leaffooted bug along a railing; seem to suit a hungry field cricket just fine; and help a camel cricket hop, sort of, away from the guy with a camera.

As for how the unfortunate bug lost its leg, it was not inclined to share that information with us, focusing instead on the message that at least it got away.

Acknowledgements

The fascinating articles “Coreidae (Insecta: Hemiptera) Limb Loss and Autotomy” by Zachary Emberts, M. St. Mary, and Christine W. Miller, and “Combat and territorial defense of Acanthocphala femorata (Hemiptera: Coreidae)” by P. L. Mitchell were used as references for this episode.

This article was first featured on Bug of the Week

Leaffooted lovers: Leptoglossus spp.

  The female leaffooted bug enjoys a tasty corn snack while engaged with her mate.

The female leaffooted bug enjoys a tasty corn snack while engaged with her mate.

 

As summer turns to fall, many insects with gradual metamorphosis, those with nymphs rather than larvae as juveniles, become adults and are more easily seen as the larger adults. This spawns a spate of requests from curious citizens to answer the question “what’s this bug?” In previous autumn episodes we met ferocious wheel bugs, deadly orange assassin bugs, and spooky milkweed bugs. This week we continue our sojourn into the realm true bugs, insects in the order Hemiptera, and learn the aromatically romantic ways of leaffooted bugs.  

How do I get around this giant hand that keeps following me? And this guy with a camera, what’s up with that? (Note the eggs of a parasitic tachinid fly deposited in the back of the adult bug; death is just around the corner).

A gaggle of leaf-footed bug nymphs dines on my pumpkin vine.

A gaggle of leaf-footed bug nymphs dines on my pumpkin vine.

On a past visit to a cornfield, in addition to bevies of brown marmorated stink bugs, I notice legions of leaffooted bugs probing kernels of corn directly at the tips of the ears or through the tough cover of the husk. Named for the leaf-like expansion of their hind legs, leaffooted bugs belong to a guild of suckers that insert their hypodermic-like mouthparts into tender plant tissue. After injecting saliva laced with digestive enzymes, they withdraw nutritious fluids from the unfortunate plant. Both the bright red and black immature stages called nymphs and the winged adults feed in this remarkable manner. In addition to sucking the life from corn, the catholic diet of leaffooted bugs includes crops such as cotton, squash, and tomatoes, trees such as oaks and maples, conifers, vines, and shrubs with representatives from fifteen families of plants.  

Apparently a stickler for detail, the mother leaffooted bug neatly lays her eggs in very straight rows.

Apparently a stickler for detail, the mother leaffooted bug neatly lays her eggs in very straight rows.

Adult leaffooted bugs live for several months and dine on many plants, but their reproduction occurs only in the presence of reproductive structures such as fruits on their host. Eggs of leaffooted bugs are curious contraptions resembling tiny barrels, tipped on their sides, aligned in a neat row. One can only wonder about the strangely linear thinking used by the bug as she neatly arranges her brood on the surface of a leaf. A circular bunghole on the side of each barrel provides the tiny nymph inside with an escape hatch once its development is complete.  

Uh oh, a doomed leaffooted bug has been visited by a tachinid fly. Larvae that hatch from eggs on its thorax will bore into the bug, consume its internal organs, and seal its fate.

Uh oh, a doomed leaffooted bug has been visited by a tachinid fly. Larvae that hatch from eggs on its thorax will bore into the bug, consume its internal organs, and seal its fate.

Like brown marmorated stink bugs we met before, leaffooted bugs release nasty scents to ward off attacks by hungry predators. However, male members of the leaffooted clan have one more aromatic trick up their sleeve. A small gland in their abdomen produces aromatic compounds with the delightful scents of cherries, vanilla, cinnamon, or roses depending on the species of the bug. Each bug has a unique blend of these compounds, known as pheromones, that allows the fair member of the species to locate and accept an appropriate mate.  But in this game of olfactory romance, danger awaits. A clan of parasitic flies called tachinids uses several cues, including the pheromones of true bugs, to track their victims. Upon sensing the pheromone, they follow the trail to its source and deposit eggs on the exoskeleton of the bug. Eggs hatch and tiny maggots drill through the exoskeleton and enter the soft tissues inside the bug. Here they will feed and develop, eventually leading to the bug’s demise. So, in the realm of romance for the leaffooted bug, beauty truly is only skin deep. It’s how you smell that really counts. But does the peril of death sometimes accompany the fragrance of attraction? Maybe only male leaffooted bugs know for sure.   

 Acknowledgements

Bug of the Week thanks Jeff Aldrich for an interesting discussion that was the inspiration for this episode. The fascinating articles“Host Plants of Leptoglossus oppositus (Say) (Hemiptera: Coreidae)” by Paula Mitchell and Al Wheeler, “Bug pheromones (Hemiptera, Heteroptera) and tachinid fly host-finding” by J. R. Aldrich, A. Khrimian, A. Zhang, and P.W. Shearer, and “Species-specific natural products of adult male leaf-footed bugs (Hemiptera: Heteroptera)” by J. R. Aldrich, M. S. Blum and H. M. Fales were used in preparation of this story.

This post appeared first on Bug of the Week

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