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!

Wasp Wednesday: Ammophila aberti

One of the most beautiful species of thread-waisted wasps is Ammophila aberti, found commonly here in southern Arizona. It actually ranges throughout western North America, east as far as Iowa, and south into Mexico. These sleek, silvery wasps are a little larger than the average Ammophila, approaching the length of A. procera, but not nearly as robust.

I was fortunate enough to come across a fairly large nesting aggregation of this species at Ft. Lowell Park in east Tucson on May 11, 2009. The female wasps were digging in a very flat area with hard, baked soil. They would literally take bites out of the earth in order to excavate their nests. Despite the abundance of wasps, it was still a challenge to get images of them. The wasps would dig a bit, fly up, settle again, and repeat the process. Consequently, I had many images with no wasp in sight!

It turns out that the nesting behavior of Ammophila aberti has been well documented. One study revealed that females may initiate more than one nest at a time. Some had simultaneously started eight different burrows, up to a dozen for one ambitious specimen. Few of the nests were finished, however. Could they be creating “dummy” nests designed to confuse parasites like velvet ants that will dig open the nests of their hosts? That would be an ingenious ploy if so.

It may also take a female wasp a long time to furnish food for its offspring. A single egg is laid on the first caterpillar to be stored in the cell at the end of the vertical or angled burrow. By the time the last caterpillar is hunted, the larva from that egg may be reaching maturity. This has been interpreted by some researchers as progressive or “delayed” provisioning, feeding the larva as it develops, but clearly this is not the case. It may simply take some female wasps longer to find a full complement of caterpillars. Also, prolonged inclement weather may delay hunting activities for the females. Lastly, temporary scarcity of prey may delay the ability of the females to find caterpillars.

Ammophila aberti might be considered something of a generalist in that it uses a wide variety of Lepidoptera species in provisioning its nests. The study cited above recorded caterpillars from five different families of moths and butterflies (and skippers) used by this wasp: Geometridae, Noctuidae, Pyralidae, Hesperiidae, and Pieridae. An average of about six caterpillars per nest was the norm for the Colorado study of this species.

Another trait exhibited by this species is prey-stealing from other wasps in the nesting aggregation. A female returning to her nest is vulnerable to robbery since she must put down her caterpillar catch to open the temporary plug on her burrow. She may be attacked by one or more others of her kind that try to wrest the caterpillar from her. The hijacking is frequently successful. Further, some wasps may actually dig open the nest of another wasp and pilfer the paralyzed cache, though this is a rarer phenomenon.

As is the case with most other fossorial (burrowing) wasps, satellite flies (Sarcophagidae: Miltogramminae) are a constant threat to parasitize the nest. Interestingly, I observed another potential parasite in the form of a bee fly, Thyridanthrax sp. The female flies were hovering over the open nests of the wasps, lobbing eggs down into the tunnels in the manner of a jet bomber. Thanks to Joel Kits for making the identification from the above image, originally published on Bugguide.net.

Clearly, there is still much to be learned about this, and the vast majority of other species of solitary wasps. So, next summer, resolve to get out and make your own observations. You are almost guaranteed of making groundbreaking contributions to our collective knowledge. Meanwhile, have a very happy Thanksgiving holiday. Good luck provisioning your table with things more appetizing (and hearty) than caterpillars 

Wasp Wednesday: Ammophila pictipennis

One of the most common, and most handsome members of the genus Ammophila east of the Rockies (and south to Mexico City) is A. pictipennis. It is black in color, with red on the abdomen, and the black areas have metallic blue reflections in the right light. The wings are orange or yellow. The orange wings and lack of any silver bars on the side of the thorax help identify the species easily.

The individual above was imaged in Ocean City, New Jersey, fairly early on an overcast morning (October 19, 2010). It is in the classic “sleeping” posture adopted by Ammophila wasps during the night and inclement weather. The wasps grip a stem with their jaws, and prop their bodies at about a forty-five degree angle with their second and third pairs of legs. They often roost in loose clusters, jockeying for the best locations before settling down. This seems like odd behavior for supposedly solitary wasps. I once found a tight cluster of several Ammophila at Smith Rock State Park in Oregon. I initially thought it was a cluster of seeds or berries drooping from a short, erect plant.

When not resting, a female A. pictipennis is a busy insect. The species usually nests in sand, but will also excavate its shallow, vertical or nearly vertical burrow in hard-baked soil. The shaft is barely longer than the wasp herself, but ends in a nearly perpendicular cell that is spacious enough to accommodate the wasp and a lone caterpillar host. The specimen below was imaged at the Orange Airport in Orange, Massachusetts, September 7, 2009. She had brought a caterpillar to the vicinity of the burrow and was preparing to open it.

Known host caterpillars used by this species include mostly cutworms like the Armyworm, Mythimna unipucta, the Spotted Cutworm, Xestia c-nigrum, the Yellow-striped Armyworm, Spodoptera ornithogalli, and the Corn Earworm, Helicoverpa zea. There is at least one record of a caterpillar of the Common Sootywing (a skipper), Pholisora Catullus being used as prey.

Image above courtesy of Giff Beaton

The nesting behavior of this species is covered in detail by Phil and Nellie Rau in Wasp Studies Afield (Princeton University Press, 1918). Their interpretation of the wasps reveals at times perhaps more about the human observers than the reality of the instinctive processes going on in the insects. Still, it makes captivating reading and creates a real appreciation for the toiling labor of these creatures, as in the process of closing a nest:

”In her next selection she seems to be more particular. She goes here and yonder, pausing at clods and tiny pebbles, sometimes lifting them or turning them over. When finally she finds one that suits her fancy…she brings it in her mandibles and, grasping it firmly, she rubs, pounds and hammers down the dirt on the top of the hole until all traces of the fill are obliterated. When she has finished, we ourselves cannot discern the spot. Her task, so skillfully done, is now at an end; she throws her tool aside a few inches and flits away with an utterly careless air, as if she had forgotten all interest whatsoever in this place – and quite possibly she has. It is interesting to note that she cannot be persuaded to use this tool before the precise time for it. Once we tossed her a tiny pebble while she was yet busy grinding to pieces her clods with a pestle-and-mortar motion, but she only took it, without ado, and laid it back on her rubbish-heap, where an annoying bit of stick and a troublesome cinder had already been placed. Later on, when she was ready for her hammer, she went directly and, to our great delight, got our pebble which she had so stolidly spurned only a few minutes before….”

The image of an ungrateful hymenopteran is at least slightly amusing.

Subsequent research has shown that the “tool use” is simply the culmination of a series of instinctive behaviors. Still, one has to wonder if there was an individual “smart” wasp that increased the survival chances of her offspring by securing the closure of the nest burrow more thoroughly in this manner. Certainly, velvet ants are expert at detecting the subterranean nests of their hosts and digging them open, so such parasites must exert strong evolutionary pressure on the wasps to prevent break-ins.

A little more technical information is available on this page from Discover Life; and once again Dick Walton provides a wonderful online video that highlights the differences in nest excavation between A. pictipennis and A. procera. See if you can make your own observations of these fascinating species.