Friday, October 21, 2016

In Praise of Aphids and Scales

When the flowers of autumn are gone, when even the asters are fading fast, where is a wasp or bee or butterfly to go for sustenance? The answer may surprise you, and turn your concept of what is a "pest" on its head.

Highly active, flying insects like bees, wasps, flies, moths, and butterflies rely on high carbohydrate resources like flower nectar to fuel their vigorous lifestyle. When those normal floral resources are no longer available, the insects must travel down other avenues. Fallen, fermenting fruits are one solution. The high sugar content of an apple, pear, or peach beginning to rot does not go overlooked by yellowjackets and paper wasps in particular.

Western Yellowjacket with conifer aphid at center left and Pine Needle Scale at center right

Pomes and other fruits are not, however, the answer to autumn insect nutrition. The overwhelming majority of sweet, sugary carbs are provided by other insects, namely aphids and scales. At this time of year, aphids in particular are feeding on plant sap in earnest, and excreting copious amounts of liquid waste called "honeydew." Infested trees are literally dripping with honeydew, and a great diversity of other insects are drawn to this equivalent of the corner bar.

Conifer aphids and their shocking large eggs

Many aphid species are also transitioning to alternate host plants for the coming winter. This is why you see so many aphids on the wing, landing on your plate at the tailgate party, and otherwise providing a tiny but prolific nuisance to outdoor activities. The aphids thus need their own fuel, and it takes a ridiculous amount of plant sap to yield that result. Xylem and phloem are notorious for being nutrition-poor, so sap-sucking insects cycle those products rapidly through their digestive systems. Liquid honeydew comes out as fast as sap is going in.

Even this Painted Lady butterfly is enjoying aphid honeydew

Social wasps tend to dominate the scene at fall aphid colonies. Because the wasp colonies are winding down, if not finished altogether, their paper palaces have emptied totally and there are now vastly more individual wasps out in the field than there were earlier in the year when many workers were inside the nest feeding the larvae, building new cells in the comb, and engaging in other housekeeping chores. With no purpose left to serve except their own individual survival, worker yellowjackets might qualify as unstable or mentally-ill were they human beings.

A blow fly literally getting its licks in

Meanwhile, flies, the normal prey of many social wasps, are free of worry from the purposeless wasps and fearlessly rub shoulders (humeri?) with them at the aphid honeydew banquet. The aphids themselves are still vulnerable to flower flies (family Syrphidae) that lay their eggs in the colonies. The fly larvae that hatch eagerly feast on the aphids, along with lady beetle larvae and lacewing larvae.

Larva of a syrphid fly that preys on aphids

Here in my Colorado Springs, Colorado neighborhood, ornamental conifers seem to be real aphid magnets. The trees are no doubt at least a little weakened by their circumstances of planting, isolated from other trees in soils that are not always compatible; and maybe (probably?) minus the symbiotic fungi they need to help them get their own complete nutritional requirements.

Striped Pine Scale on ornamental pine

Scale insects, too, afflict these pines, firs, and spruces. Scale insects are relatives of aphids, but are even more sessile, often covered in a hard, waxy shell secreted by the insect. The "lump" is thus a living lid over the insect that created it. Like aphids, scales secrete honeydew as a waste product. If you are unaccustomed to recognizing scale insects, it is easy to be perplexed by the wasp and fly activity. Even butterflies and moths will be flitting around inexplicably.

A tiny ichneumon wasp visits the honeydew saloon

So, the aphid colony is a bustling place at this time of year, the last epicenter of "bug" action before the leaves finally fall and the killing frosts finish off those insects still commanding our attention. They still survive, of course, hidden from view, often in life cycle stages we would not recognize as insects until spring returns them as such.

The yellowjacket trap at bottom right was not nearly as attractive as the "aphid tree" next to it

Enjoy this last hurrah of bugdom. You can easily approach the buzzing horde without fear, so intent are they on feeding. Worry not of stings, though be careful where you reach and step. This is no season to be barefoot to be sure.

Sunday, October 16, 2016

Review: Diving Beetles of the World

Johns Hopkins University Press is an underrated publisher of natural history titles for both professional scientists and general audiences. Their latest example of impeccable quality is the book Diving Beetles of the World: Systematics and Biology of the Dytiscidae, by Kelly B. Miller and Johannes Bergsten. It is somehow fitting that a relatively ignored family of aquatic beetles gets its "coming out party" delivered by a publisher assumed to be mostly a purveyor of medical books.

Diving Beetles of the World should be a model for a serious and thorough treatment of any entomological subject. Every aspect of the biology, ecology, and classification of the family Dytiscidae is covered here. It is this placement of the beetles in a larger context that is so vital, and so often lacking in other technical publications devoted to various insect taxa. Creating an appreciation for a neglected family of organisms is no small feat, and this publication vastly exceeds expectations.

Rhantus gutticollis from Colorado

It helps greatly that the book is lavishly illustrated with detailed images of perfectly prepared specimens of the beetles themselves. Even a casual student of entomology will feel comfortable at once. Furthermore, keys to the subfamilies, tribes, and genera of diving beetles are likewise illustrated with line drawings and clear, magnified images of critical parts of the beetles' anatomy. Were that not enough, there are also maps showing the global distribution of each genus.

The summary for each genus includes a "diagnosis" of physical characters peculiar to that genus, in case you missed anything during your journey through the keys; a history of classification and relationships to other genera; a description of diversity that includes the number of species currently recognized for that genus; a natural history indicating what habitats and niches the particular genus occupies in nature; and finally a distribution description that complements the maps.

Thermonectus marmoratus from Arizona

The authors, one American and one European, fully recognize the fluid nature of insect taxonomy and have cited virtually every paper and publication written previous to this current work. This sets the stage perfectly for ongoing and future investigations into the Dytiscidae.

Considering that aquatic ecosystems are arguably the most critical habitats on the planet, this book deserves to have an impact far beyond entomology. Every aquatic biologist, environmental consultant, and citizen scientist needs to have this volume in their library, or at least seriously consider it. Should you not make the purchase yourself, please suggest it to your university library.

Colymbetes sculptilis from Massachusetts

Indeed, the only unfortunate aspect of this tome that does not recommend it is the price: $150.00 U.S. Easy for me to enjoy my review copy while my readers are looking at a major expense, no doubt. Still, this is an important work, not just a gift for "the entomologist or naturalist who has everything." How to reconcile quality work with an affordable sale price is a question for another blog, and believe me I am open to suggestions. In the case of Diving Beetles of the World, the product commands the monetary value assigned to it.

Note: Images other than the book cover are my own and are not featured in the book.

Friday, October 7, 2016

The Great Grasshopper Hunt II

I am terribly behind in chronicling field experiences I have participated in this summer, including the second annual(?) "grasshopper hunt" co-sponsored by Mile High Bug Club and the Aiken Audubon Society. Our first one was held last year at Homestead Ranch Regional Park near Peyton, Colorado. This time we opted to head farther south and a little farther east to Chico Basin Ranch; and we were led by grasshopper expert Bill Maynard.

Our intrepid participants © Bell Mead

The ranch is a sprawling 87,000 acres that straddles the El Paso and Pueblo County line. Its wide array of habitats, from sandhills to artificial wetlands, makes for high biodiversity, especially among insects and grasshoppers in particular. In only a few hours our party of roughly ten people observed forty (40) species of grasshoppers, plus many other insects and arachnids.

Pink form of the Broad-banded Grasshopper, Trimerotropis latifasciata

Bill is rather new to the study of grasshoppers, but he quickly masters many aspects of natural history. He is already recognized as a leading authority on birds and dragonflies, with many state and county records to his credit. It is only a matter of time before the same can be said of his expertise in the order Orthoptera to which grasshoppers belong.

Rather than overwhelming you with images here, I will direct you to the Mile High Bug Club Flickr Group where you can peruse the image collection at your leisure.

Snakeweed Grasshopper, Hesperotettix viridis

We would be remiss if we did not also acknowledge the hospitality of the Chico Basin Ranch staff, especially Tess Leach and her family. Her two children were especially curious, and remarkably patient and gentle in their approach to the many grasshoppers we saw.

Three-banded Grasshopper, Hadrotettix triafasciatus (foreground), signaling to a Broad-banded Grasshopper (background) to get out of its territory

The intense heat of that August 6 day sent some members of our party packing by about noon, but who could blame them? The Plains Harvestfly, a type of cicada, made it seem hotter still with its loud, oppressive buzz. All in all, the "expedition" was a resounding success, and no vehicles or people were injured during the odyssey.

Plains Harvestfly, Neotibicen dealbatus

While plains and deserts are prime habitats for grasshoppers, you can find them nearly everywhere. You will be surprised by the number of species you can discover in your own backyard, neighborhood park, vacant lot, or any other patch of wildness. Even now, with the first frosts approaching, grasshoppers are among the few insects left in any abundance. Go take a look for them.

Friday, September 16, 2016

A Beetle Mimicry Complex

This week, on one of my daily walks around our Colorado Springs neighborhood, I encountered a beetle on the sidewalk that gave me reason to pause. I initially dismissed it as a species of soldier beetle that is extremely abundant at this time of year, but something looked a little "off." Sure enough, it was something else; and that got me thinking about mimicry among all these beetles.

Blister beetle, Epicauta stuarti

The beetle on the sidewalk turned out to be a blister beetle, Epicauta stuarti, a species I had not seen before. Blister beetles, family Meloidae, are well known for containing high concentrations of the potent, irritating chemical cantharidin. Blister beetles exude the chemical in liquid form from leg joints and from between other body segments if the insect is squeezed or crushed. The chemical goo can raise painful, scarring blisters on sensitive skin; it can be fatal if ingested.

Ironically, many, if not most, blister beetles don't advertise their toxicity with bright "warning colors." Epicauta stuarti is one that does, but the interesting part is that its pattern of black and orange is very similar to that of our two common autumn soldier beetles. Soldier beetles are in the family Cantharidae, and they also have chemical defenses, which they secrete from abdominal glands. The Colorado Soldier Beetle, Chauliognathus basalis, is common on the plains. Its close relative, C. deceptus, replaces it in the foothills and mountains.

Colorado Soldier Beetle

This kind of shared color pattern that reinforces predator deterrence is called Müllerian mimicry. Both animals can back up their colorful advertisement of toxicity with actual chemical weaponry. This is a very interesting example of mimicry, but it doesn't end here. Other local beetles have jumped on the bandwagon.

End Band Net-wing Beetle, Calopteron terminale

Also appearing at this time of year is the End Band Net-wing beetle, Calopteron terminale. They generally occur in far fewer numbers than the soldier beetles, but can be mistaken for them with just a passing glance. It is widely assumed that net-winged beetles (family Lycidae) are distasteful to predators, because they have colorful patterns in many cases. Whether this has been proven I do not know.

Net-winged beetles may exaggerate the effect of their wardrobe by raising and lowering their wing covers (elytra) in a unique display. As adults, they feed on nectar, and the "honeydew" secreted by aphids and related insects as a sweet liquid waste product. Larvae of netwing beetles feed on fungi or metabolic products of fungi. Whether this diet can be converted into toxic compounds is debatable.

Longhorned beetle, Crossidius discoideus

While the jury may still be out on whether net-winged beetles are indeed toxic, there is no question that yet another mimic in this complex is pulling one over on predators. The longhorned beetle Crossidius discoideus fools us into thinking it is dangerous to eat by mimicking the pattern of the solider beetles. It can even be found on the same flowers as the soldier beetles and is difficult to easily separate from them, except for its long antennae. This brand of mimicry is called Batesian Mimicry, whereby a harmless animal masquerades as a dangerous one.

Crossidius discoideus has no common English name. As a larva, it bores in the root crowns of Broom Snakeweed, Gutierrezia sarothrae, or Jimmyweed (Isocoma spp.). The adults feed on flower pollen and nectar. Broom Snakeweed is also where the blister beetles hang out, so I may have to look more thoroughly for them now.

Longhorned beetle, Batyle suturalis

Yet another kind of longhorned beetle, Batyle suturalis, appears just before the populations of soldier beetles explode. Is it, too, taking advantage of a similar color pattern to gain "cover" from predators? What I would like to know is which of the truly toxic beetles started this whole complex. The blister beetle? The solider beetles? We will likely never know, and that is part of the appeal of entomology. It is an endlessly curious endeavor, seeking the answers to more puzzles than mankind will ever unravel.