Metallica

My last entry on cuckoo wasps prompts me to pen (keyboard?) a complementary article on the metallic green solitary bees that are frequently mistaken for cuckoo wasps. Indeed, to the untrained eye they appear essentially identical, so how do you tell the difference?

Perhaps the best way to tell cuckoo wasps from those metallic members of the solitary bee family Halictidae is by behavior. Consider this:

• Cuckoo wasps are seldom found on flowers.
• Metallic bees are usually quite common on flowers.

Both cuckoo wasps and “sweat bees” are fond of the liquid waste products (honeydew) of aphids and scale insects. I once found a huge number of sweat bees on a small, infested oak tree in Cincinnati, Ohio.

How the different insects move about is also telling:

• Cuckoo wasps flit about, and once they have alighted dash about with quick, jerky movements.
• Sweat bees tend to fly and alight more directly, and move less swiftly than cuckoo wasps.

Both the wasps and the bees will sometimes pause to preen themselves, usually resting on a sunlit leaf to do so, but the bees generally take longer to do this than the wasps do. Male sweat bees will perch on leaves and stems to watch for passing females.

Appearance of the two insects is often not sufficient to distinguish them from each other, but if it has pollen on its hind legs it is not a cuckoo wasp. Only female sweat bees collect pollen, using brushes of hairs called “scopae” on the hind legs to store the grains for the trip back to the nest burrow.

There are several different genera of metallic green bees in the Halictidae family, their relative abundance changing somewhat with geographic location. The most widespread and easily recognized may be those in the genus Agapostemon. Male Agapostemon species have only the head and thorax metallic green. The abdomen is banded in black and yellow pigments. Females of Agapostemon virescens have a black abdomen with bands of white hairs (see image above). Females of most other Agapostemon are wholly metallic green, but also rather hairy.

More confusing are members of the tribe Augochlorini (image immediately above, and below). The three genera in this tribe, Augochlora, Augochlorella, and Augochloropsis are virtually identical. Unless you are already an expert on them, you have to collect a specimen and put it under a microscope to deduce which genus it belongs to. All are bright metallic green, blue-green, though the common eastern U.S. species Augochlora pura is frequently brassy, coppery, or bronze in color.

The nesting behavior of the sweat bees is quite remarkable as well. While cuckoo wasps have no nest, instead seeking the nests of other solitary wasps where the female cuckoo lays her eggs, sweat bees excavate burrows in the soil (or in rotten wood in the case of Augochlora). Consequently, both cuckoo wasps and sweat bees can sometimes be seen investigating cavities in dead standing trees or logs.

The genera Augochlora and Augochlorella include at least some species that exhibit communal nesting or primitively social biology. This is also true of Agapostemon virescens, where several females may share one nest entrance. I remember discovering a nest of this species in a neighbor’s yard in Portland, Oregon when I was a child. I would spend hours watching the females come and go, and the “guard” bee pop its head out of the single nest entrance atop the little mountain of excavated soil (“tumulus” as scientists call it). Sometimes she would come almost completely out of the nest, looking around anxiously for signs of danger.

It is difficult not to assign such insects as “heroes” or “villains,” or ascribe human personality traits to them. They are very captivating organisms once you get to know them. Do enjoy watching them, and share your observations where you are able. There is still much to learn about them. Given our changing environment and climate, chronicling the adaptations of bees and other organisms will be paramount to successfully protecting them and the pollination services they provide to plants.

Cuckoo for Cuckoo Wasps

You would be hard-pressed to find lovelier insects than the cuckoo wasps of the family Chrysididae. They are clad in gem-like colors of emerald, ruby, jade, and even copper and gold. These wasps are small, and stingless, too, making them much less intimidating than other members of the order Hymenoptera.

The life histories of these unique insects remind one of a spy thriller or great crime caper. While a few obscure, tiny cuckoo wasps parasitize the eggs of walkingstick insects, most female cuckoo wasps lay their eggs in the nests of other kinds of solitary wasps, or solitary bees, exposing themselves to the jaws and stings of much larger, stronger species. The cuckoo wasps have what amounts to a “bulletproof vest” in their extra thick exoskeleton that acts like a suit of armor. The wasps can also roll themselves into a compact ball to protect their faces, legs, and other vulnerable body parts, much like a turtle or tortoise can retract into its shell, or an armadillo rolls up.

That durable cuticle is pitted, grooved, and otherwise sculptured, creating facets that reflect various wavelengths of light and give the insects their bright metallic colors. Pigments have nothing to do with their jewel-like quality.

Different species of cuckoo wasps have different “hosts” for their larval offspring. Some species specialize in breaking and entering the nests of mud daubers while others spy on wasps that dig nest burrows in the soil or sand. When the mother host species is away from the nest, the cuckoo sneaks in to lay her own egg. She has special, telescoping abdominal segments that complement an egg-laying organ called an ovipositor, helping her to hide her egg among the paralyzed insects or spiders harvested by the host wasp as food for its own larvae.

The egg of the cuckoo wasp hatches after the larva of the host species. The cuckoo larva then attaches itself to the host larva, and waits patiently as the host larva eats and grows, reaching the “pre-pupal” stage. At this point the cuckoo larva begins consuming the host larva, eventually killing it in the process. The mature cuckoo larva then pupates and emerges from the nest as an adult cuckoo wasp sometime later.

An alternative life history is found in some species where the cuckoo larva eats the host’s egg or young larva, then scarfs down the food stored for the host (paralyzed insects, spiders, or pollen and nectar).

Adult cuckoo wasps fuel themselves on carbohydrate-rich foods. Oddly, few species seem to visit flowers with any regularity. Instead, you are more likely to find them around aphid colonies, lapping up the “honeydew” excreted by the sap-sucking aphids as a sugary, liquid waste.

Cuckoo wasps can also be found on the exterior of old barns, on dead, standing trees, and similar situations where they hunt for the nests of their hosts.

Chrysidids are more diverse in western North America than they are in eastern North America, but are often harder to find in the west. Few resources exist to help you to identify them, either, though there is a wonderful new interactive key to Cuckoo
Wasps of Eastern North America at Discoverlife.org. The website BugGuide.net also has many images of cuckoo wasps sorted at least to the level of subfamily or tribe. The best internet resource is devoted to European cuckoo wasps and is dubbed ”Chrysis.net.

By all means, enjoy searching for cuckoo wasps in your own backyard, local parks, and elsewhere. There is still much to be learned about them and room for scientific contributions from everyone.

Mother (Nature's) Day in Madera Canyon

Madera Canyon in the Santa Rita Mountains is one of my favorite places to visit, so I was delighted to join other folks from the Southeast Arizona Butterfly Association (SEABA) for a Mother’s Day outing there on May 9. I even learned of additional trails that I was previously unaware of. Thanks to trip leader Gary Jue for a great time.

We had hardly gotten beyond the parking lot at the mouth of the canyon when someone spotted this lovely little Marine Blue, Leptotes marina.

There were still many wildflowers blooming, but ironically that did not help us find many butterflies. What seemed to be more important was the fact that water was still flowing through the canyon.

Following trails to the rocky streambed led us to the creek where we found the wet sand and muck along the margins alive with “puddling” butterflies. Butterflies of many species (and the males in particular) will sip from wet sand and soil, taking up important minerals in the process. The butterflies usually excrete copious amounts of water as they sequester those nutrients. Males build up a reservoir of these substances that they then transfer to the female during mating. Perhaps those chemical compounds help to strengthen or nourish her eggs.

Among the sippers at the butterfly bar was this White-barred Skipper, Atrytonopsis pittacus. So oblivious are butterflies when they are imbibing at the stream bank that it is relatively easy to approach within inches of them.

Streams and creeks also provide natural corridors or “flyways” for butterflies. Those species that utilize riparian trees and plants as hosts for their caterpillars have an added reason to be there. Males of those species often defend territories that include those host plants. Such is the case with the Red-spotted Purple (now considered one variation of the “White Admiral”), Limenitis arthemis.

This male perched repeatedly, but the wind prevented too many photo ops. It would also periodically engage another male in aerial battles.

Butterflies were also present in the larval stage. One sharp-eyed SEABA member spotted this caterpillar of the Painted Lady, Vanessa cardui on the stalk of a thistle.

Crack butterfly authority Doug Mullins identified it in part by the silk webbing on the leaves of the thistle, created by the caterpillars to insulate them from the hot sun while they feed. Why any insect in its right mind would want to eat a spiny thistle leaf is beyond me. The caterpillar must hatch from the egg, take one look at the host plant and say “Gee, thanks, mom!”

We caught glimpses of plenty of other butterflies on the trip, including the Two-Tailed Swallowtail, Empress Leilia, Queen, Sleepy Orange, Orange-headed Roadside Skipper, Spring Azure, and Tiny Checkerspot. The last one I saw personally was worth the wait.

On my way down the trail to the parking lot at the top of the canyon I spied what I almost dismissed as “just” another Spring Azure. It didn’t look quite right, though, and indeed it turned out to be an Acmon Blue, Plebejus acmon, a common but very pretty little butterfly.

It took a great deal of patience on both my part and the insect’s before I was (permitted/able) to get a nice picture. Thank you Mother Nature, happy Mother’s Day in the grandest sense.

Apologies, Excuses, Suggestions

The loyal followers of this blog deserve to be dazzled and amazed much more frequently than the writer has been able to do lately. I sincerely apologize for the time lag and anticipate that things will improve soon. Today I will do a little explaining.

I am delighted to report that part of the reason I have been “missing in action” is because I have acquired some assignments that, believe it or not, are actually paying me for online content I am creating. As a co-moderator with Mandy Howe, I’m monitoring submissions to SpiderIdentification.org for a modest monthly wage. I want to express my sincerest thanks to webmaster Kyle Williams for this opportunity.

Kyle had also purchased the domain name “DustMites.org,” but soon sold it to another individual. That person, Tim McGuiness, is out of the same amazing mold as Kyle in that he, too, has offered to pay me for creating content. I am in the midst of doing that right this instant, and am facing a pretty tight deadline. The research alone has had my head swimming. Obviously, I am also grateful to Tim for his generosity. Both the spider and dust mite websites will eventually include advertising that may generate more income still for all involved, but first things first.

Since it is springtime, I have also found myself out in the field quite a bit, though my allergies to pollens have sometimes made for miserable outings. It has also been extremely windy here in southeast Arizona, making it difficult to get respectable images of flowers, insects, birds, and other organisms to illustrate this blog with. I am very appreciative of my friends Margarethe Brummermann, Ned Harris, Fred Heath and his wife Mary Klinkel, John Rhodes, and others for including me in their own field trips.

I am hoping that all of you are also getting out and about, but if not, may I suggest investigating some of the blogs that I follow? Margarethe just started her own, all about Arizona beetles, bugs, birds, and more. My entomological colleague David Almquist also has a new blog. Both are listed, along with perennial favorites like “Beetles in the Bush” by Ted MacRae, on the sidebar of this blog.

Thank you again for your patience and understanding. May you enjoy the season.