Wednesday, December 29, 2010

Wasp Wednesday: Chirotica

I never expect to encounter wasps in the middle of December, but then I also don’t go out looking for them at that time of year. A trip to the Sabino Canyon Recreation Area north of Tucson on December 19 has me re-thinking that assumption. I was surprised by the number and diversity of wasps I saw. Among the more interesting was an ichneumon wasp I later identified as belonging to the genus Chirotica.

Fred Heath, a volunteer naturalist at Sabino Canyon, had invited me along for a short hike in the late morning and early afternoon. He knows the area very well and was able to point out everything from plants to puffballs. On a willow tree full of bagworms (moth family Psychidae), a flash of movement caught my eye. A very elegant-looking ichneumon wasp was exploring one of the branches of the willow.

Ichneumons are notoriously quick to fly at the slightest movement, so I did not expect this wasp to stick around. Much to my surprise it simply continued its searching behavior, allowing me a couple images with my camera before it departed. What was this female looking for?

It turns out that the four North American species of Chirotica are parasites of….bagworms! It all made sense, and a series of images on the website even show one of these wasps investigating a bagworm cocoon.

The “stinger” on my specimen is actually the female’s egg-laying organ, called an ovipositor. She does not use this structure as a weapon in self-defense and so is harmless to inquisitive people like me. Not that I could have caught her by hand anyway.

Anyone with an infestation of bagworms would likely welcome more of these wasps, but I honestly have no idea just how common (or scarce) they are. You can learn about the known distribution of our four species by using the Database of Hymenoptera in America North of Mexico. Bob Carlson, an expert on ichneumon wasps who is now retired from the National Museum of Natural History (Smithsonian) put together that part of the database.

Ichneumons are among the most diverse group of insects on the planet, so even an “armchair entomologist” can make significant contributions to science by documenting specimens through collection and imaging, but especially through rearing the wasps from host insects like butterfly and moth caterpillars.

Monday, December 27, 2010

Pygmy Mole Crickets

I know! What the heck is a “pygmy mole cricket?” Well, they are actually more akin to short-horned grasshoppers than mole crickets. I have known about them for some time, but finally saw two “in the wild” in the Sabino Canyon Recreation Area last Sunday, December 19.

The family Tridactylidae occurs on all the major continents except Antarctica, but most species are apparently tropical. There are only two species currently recognized in North America, and the one I encountered is likely Neotridactylus apicalis, the “Larger Pygmy Mole Cricket.” That species ranges from extreme southern Ontario east to Massachusetts, south to Florida, and west to southern California.

At about the size of a grain of rice (ok, from 5.5-10 mm), they are not very noticeable. Couple that with their habit of tunneling under the sand along the margins of streams, rivers, ponds and lakes, and it is no wonder they are not more familiar to naturalists. They move rather slowly, or at least this pair did as they crept up the surface of a streamside boulder. The hind legs of these insects are positively enormous, and the hind femora alone usually conceal the folded wings of the adults. The front wings are leathery and reduced to short stubs, while the membranous, pleated hind wings extend just beyond the abdomen when folded.

I was pleased that these individual specimens were so tolerant of a close approach with my camera (though I wished for a really good macro lens), because when they finally did decide to jump….Game over! They seemed to disappear into thin air. There was certainly no finding them again.

The physics of these jumps is remarkable, as revealed in the abstract for ”Jumping Mechanisms and Performance of Pygmy Mole Crickets” in the Journal of Experimental Biology, 2010 Jul 15;213(Pt 14):2386-98, by M. Burrows and M. D. Picker. Were a human even capable of such a feat, he would likely pass out from the G-force alone.

Pygmy mole crickets, which are also known as pygmy sand crickets or pygmy mole grasshoppers, apparently ingest sand particles and whatever algae and other organic matter adheres to them. Their subterranean burrows extend 2-3 centimeters below the surface, and females create brood chambers at the bottom of their tunnels.

Do keep an eye out for these little wonders. You are likely to find other insects in the same habitats, like the grouse locusts I’ll discuss in the next week or two. Happy hunting.

Wednesday, December 22, 2010

Wasp Wednesday: Campsomeris

I could never have imagined that I would confront another mystery wasp in the middle of December, but there it was: an e-mail from a friend describing what I knew (even in the absence of an image) was a species of wasp that had been recorded only recently in Arizona, and far closer to the Mexican border than in the Sabino Canyon Recreation Area where my friend’s sighting took place.

Fred Heath is an outstanding naturalist, author of the Introduction to Southern California Butterflies, and a member of the Sabino Canyon Volunteer Naturalists. On a visit to the area on Tuesday, December 14, he and others spied a male specimen of Campsomeris ephippium on blooming flowers of Desert Lavender (Hyptis emoryi). Fred didn’t get an image, but this wasp is so conspicuous and distinctive that it didn’t matter.

Fred posted a message on the e-mail list for the Sabino Canyon Volunteer Naturalists, sparking David Lazaroff, a founder of the SCVN, to go looking himself, camera in hand. The above image is used with David’s permission, and what a great picture it is. The long antennae, relatively slender body, and “pseudostinger” at the posterior of the abdomen reveal the gender of this specimen. Females, more robust with shorter antennae, have the real deal: a retractable stinger used to subdue the scarab beetle grubs that are the hosts for its larval offspring.

I would not have known what this was had it not been for this image from the spring of 2009. Up until that time, Campsomeris ephippium was known only from south Texas, and south to Ecuador.

Fred Heath and I went back to Sabino Canyon on Sunday, December 19, but failed to find the beast. Ironically, we did manage to spot a few males of the common local species, Campsomeris tolteca. They were hungrily feeding on the nectar of Coreocarpus arizonicus (Little Lemonhead) beside Queen butterflies and Mexican Yellows (also butterflies).

Campsomeris wasps belong to the family Scoliidae, all of which are known parasitoids of scarab beetle grubs. A parasitoid is a parasite that invariably kills its host. Female scoliids, with their heavy, spiny legs, dig up a scarab grub, sting it into brief paralysis, and then lay a single egg on the beetle larva. Then the wasp leaves the scene. The grub eventually regains consciousness and control over its motor skills (such as they are), resuming its underground existence feeding on the roots of plants. Meanwhile, the wasp egg hatches and the wasp larva begins feeding as an external parasite of the beetle grub.

I hope to eventually find more specimens of Campsomeris ephippium, and females of some of our other scoliid species here in Arizona, but I certainly enjoy the pleasure of the hunt regardless of the outcome. Special thanks to Fred Heath for allowing me to join him in the great outdoors. Thanks again to David Lazaroff for use of his fine image.

Wednesday, December 15, 2010

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 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.

Wednesday, December 8, 2010

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.

Sunday, December 5, 2010

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.

Wednesday, December 1, 2010

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!