Wasp Wednesday: Mellinus

It never fails that just when I think I’ve seen it all I get surprised by some “new” insect. That happened on September 5, 2009, when I photographed a small wasp carrying a fly. Surely that must be a species in the Crabronini tribe, I told myself. I was dumbfounded when I downloaded the image and realized it was nothing I was already familiar with. Detective work ensued.

I posted the image above to Bugguide.net in hopes that another wasp expert might recognize it. Possible identifications were offered, but none of the suspects matched in terms of either morphology or prey selection. The mystery deepened.

I next went to my good friend and mentor Arnold Menke, a hymenopterist retired from the USDA Agricultural Research Service at the National Museum of Natural History. He literally wrote the book (Sphecid Wasps of the World) on the larger group of wasps that my specimen belongs in. Arnold also enlisted the help of Woj Pulawski at the California Academy of Sciences. We were conducting our correspondence over e-mail.

Meanwhile, my own continued research led me to believe that I had imaged a female Mellinus bipunctatus. I found images of other species in that genus carrying flies in a similar manner; and a close look at my image seemed to show that the wasp has a petiolate (“stalked”) abdomen, a character not shared by other fly predators of similar size (8-10 millimeters).

Arnold was initially unconvinced, believing it to be in a different subfamily. I had to agree, except for the fly prey factor. I created a guide page back on Bugguide for the genus Mellinus and moved my image there, adding my suggestion for the species. That coincided with a visit to Bugguide by Matthias Buck at the Royal Alberta Museum in Edmonton. He was delighted because Mellinus bipunctatus is a rarely-seen species.

Back in Arizona this year, I imaged another species of Mellinus while photographing small blow flies on some scat at the edge of Sabino Creek in the Sabino Canyon Recreation Area on April 13, 2010 at about 1 PM. Like pigeons reacting to a falcon, all the flies flew when the wasp alighted.

This image was yet another challenge, and Arnold sent me a couple reprints on the genus this time, one of which he co-authored. I also posted a link to my image on the professional entomology listserv I subscribe to, and received positive responses from Doug Yanega at UC Riverside, and James R. Wiley at the Florida State Collection of Arthropods. Doug suggested there was a possibility it was a new species given how uncommon these wasps are. Jim Wiley suggested the species M. imperialis, which was supported by Matthias Buck and also by Carl Olson, Associate Curator of Entomology at the University of Arizona. Carl found a specimen collected by Richard Bailowitz at Organ Pipe National Monument in 1987.

I went from the exhilaration of a potential new species to a possible state record, to not even a county record (dang western states with those huge counties…grumble, grumble). Ah, well, I know Rich and I’m happy that he got the first Arizona record.

Oh, you want to know something about the biology of these wasps? Virtually all we know comes from observations of the European species M. arvensis which is oddly common. These are “digger” wasps, excavating burrows in sandy soil, often in the company of other members of their species. The burrows extend 30-50 centimeters underground, terminating in one to ten individual cells. Four to nine paralyzed flies are provisioned in each cell, an egg laid on the last victim. The cells are closed with an earthen plug when finished, but the entrance to the main tunnel is left open while the female hunts.

The wasps hunt mostly in the vicinity of fresh manure, with males staking out territories there and intercepting females to mate with them. Observers note that the females stalk their prey in feline fashion, slowly creeping up behind an unsuspecting fly, then pouncing and pinning the fly’s wings while stinging it underneath its body. Once the prey is subdued, the wasp turns it over, grabs the fly by its mouthparts, and flies off.

Given that the bulk of the prey taken by Mellinus are muscoid flies (house flies and their kin), it is a shame the wasps are not more plentiful. They could be employed as biological controls of such “filth flies,” thereby improving rural sanitation.

Special thanks to all of those mentioned above, plus Julieta Bramblia who enlisted Jim Wiley’s help on my behalf. Entomologists rarely work alone, and we are privileged to have so many helpful colleagues.

Wasp Wednesday: Ammophila wrightii

Ok, I couldn’t resist writing about one more species in the genus Ammophila, if only because it represents a distinct pair of species that differs considerably from other members of their species group. Ammophila wrightii, and its relative A. formicoides, are mimics of ants.

I was fortunate to find this specimen nectaring on flowers of Burroweed (Isocoma tenuisecta) at the Arizona Sonora Desert Museum just west of Tucson on the afternoon of September 26, 2010. One rarely sees this insect on flowers. Females are usually actively crawling on the ground in the manner of harvester ants. They are easily mistaken for those social insects and thus frequently overlooked.

This is one of the smaller species of Ammophila (under 20 mm), and colored almost uniformly reddish brown. The species ranges from California and Nevada east to northern Nebraska and south to at least the Mexican border. There is one record from north-central Oregon. Oddly, most western specimens have three submarginal cells in the front wing while specimens from the eastern portion of its range have only two submarginal cells. Why the extra wing vein in some specimens remains a mystery. Both A. wrightii and A. formicoides also have a low, flattened pronotal collar (base of the “neck”). It is hard to believe, but both species are in the same species group as the gargantuan Ammophila procera!

Ammophila wrightii exhibits at least one rather primitive behavioral characteristic: The nest burrow is excavated after a prey item is collected, instead of beforehand. Burrows are vertical in orientation, and only inchworm caterpillars from the moth family Geometridae are recorded as hosts.

Not a great deal of field observations on this species have been recorded since C. H. Hicks published his in the journal Psyche in 1934. That was back when the species went by the name Sphex wrightii. Obviously, there is room for improvement. Go forth my friends, and seek your fortune of knowledge.

Special thanks to my friend and mentor Arnold Menke who identified my images.

Chiricahua Whites

Mary Klinkel, one of the volunteers for the Butterfly Magic display at the Tucson Botanical Gardens, invited me to join her in her quest to find a female Chiricahua White butterfly, Neophasia terlooii, in Madera Canyon on November 17. I eagerly accepted since I had never seen this species myself. The day was warm and clear, and we saw many butterflies and other insects.

We drove to the very end of the road and struck out on the trail at around 11:30 AM. Walking up the dry streambed we eventually encountered a trickle of water, and insects seemed to appear instantly, out of thin air. Among them was a lone male Chiricahua White. He quickly vanished from view, however, actively crawling into the leaf litter to reach the water underneath. I approached cautiously, and after several minutes succeeded in spying the sneaky devil.

The Chiricahua White is restricted in its geographic distribution to the isolated “sky islands” of southeast Arizona in the U.S., but also occurs in Mexico. Many of you are probably more familiar with its cousin, the Pine White, Neophasia menapia. The Pine White ranges from southern British Columbia south to California and northern Arizona, east to the Rocky Mountains. The caterpillars of both species feed on conifers, the Chiricahuan White apparently restricted to Ponderosa Pine and Engelmann Spruce.

There are two generations of the Chiricahuan White, one in early summer and one in autumn. The fall population seems to be much larger than the summer population. Males tend to outnumber females, which is normally the case in most insects. How do you tell the genders apart, though, and why was Mary so anxious to find a female?

Many species of butterflies exhibit “sexual dimorphism,” whereby males and females may appear radically different in appearance. Color, size, and even wing shape can vary in these cases. Females of the Chiricahuan White are, of all things, Halloween orange in color, with black wing veins.

I was lucky to see this tattered female (above) alight along the edge of the stream, where she remained while I called to Mary. Mary worked her way back down the trail and then stalked the butterfly with camera in hand. Eventually, she was able to gently coax the creature onto her finger. It was a real Kodak moment and a thrill for Mary.

We managed to find one more male on the way back down the trail. He was in perfect condition but seemed to fly clumsily, becoming tangled among grassblades before finally extricating himself and settling on this rock. I suspect that many specimens of this species simply drown in attempts to drink.

NOTE: This species is also known as the “Mexican Pine White,” with alternate spellings, or misspellings of the species name: terlooti and terlootii. Another excellent account of this species can be found at the ”Firefly Forest” website.

Wasp Wednesday: Ammophila nigricans

We’re going into overtime on “Ammophila Month,” so we can conclude with what may be the most elegant and impressive of all the eastern species in this genus: A. nigricans. This species is easily as large as A. procera, but readily identified by the lack of silver stripes on the thorax, the overall deep blue-black body with red on the abdomen, and the black wings.

I was fortunate enough to encounter this particular specimen around 5:00 PM on July 5, 2009 in South Deerfield, Massachusetts. She was in the process of finding a place to settle in for the night and was quite tolerant of my photographic activities. This is often the best time to look for Ammophila wasps in general, because of this “sleeping” behavior.

The wasps will grip a grass stem or twig with their jaws, then prop their slender bodies at about a forty-five degree angle away from their perch. It doesn’t look very comfortable, but this stiff posture appears to suit the wasps just fine. You can sometimes find several species of Ammophila in the same general vicinity as they bed down at dusk. There are certainly often several individuals of the same species in close proximity, as in the image below of an unidentified species.

When they are awake, females of Ammophila nigricans are all business. Each wasp digs a vertical or angled burrow in clayey or sandy soil, terminating in a horizontal chamber at the bottom. Once the nest is excavated, it is off to find a large caterpillar. Known hosts include the larvae of underwing moths (Catocala spp.), the locust underwing (Euparthenos nubilis), and zale moths (genus Zale). Those are hefty caterpillars, but then they are destined to feed the larva of a very robust wasp. This YouTube video may or may not depict A. nigricans, but the searching behavior must be very similar at the least. The female wasp is not likely to locate a caterpillar based on movement or color, as the caterpillars are very cryptic and usually resting stock still, feeding at night to avoid predators like the wasp. So, she must find her prey by touch.

I hope you have enjoyed this introduction to this genus of wasps, and that you are excited to find specimens of your own once the warm weather returns to your location. Meanwhile, feel free to share your past observations here. Happy holidays to you!