Two Spiny-butts

There is no way around it. The most apt description of most tachinid flies is "spiny-butt." The abdomen of a good many members of the family Tachinidae is covered in long, obvious spines. Why? I haven't found an explanation, but that physical characteristic helps one to immediately recognize these flies as something other than a house fly, blow fly, flesh fly, or other similar dipteran. That said, two large tachinid flies are frequently confused with each other: Adejeania and Paradejeania.

Adejeania vexatrix

Here in western North America, these two animals are commonly observed as they take nectar from late summer and fall wildflowers. I, for one, can never remember which one is which. Ok, so one of them has beak-like mouthparts, is slightly smaller than the other, a bit brighter in color, and declines in abundance toward autumn....

Ah, it is Adejeania vexatrix that has these characters! The "beak" is somewhat unusual in the Tachinidae, and it is the elongated palps that form a sheath around the remainder of the mouthparts. This species ranges from British Columbia and Alberta south through California, Arizona, and New Mexico. Adult flies are on the wing in July and August, but in the more southerly reaches of their distribution can be found in September or even October.

It is known that this fly is a parasite of caterpillars, but the exact host species has yet to be documented. When a caterpillar yields an organism other than the adult moth or butterfly, it can be a real challenge to identify what kind of Lepidoptera it was *supposed* to metamorphose into.

Macromya crocata strongly resembles A. vexatrix, is found in similar forested habitats, but lacks the "beak" of its look-alike. The same information applies to Hystricia abrupta, another common species frequently mistaken for A. vexatrix.

Paradejeania rutilioides is even more robust, and spinier, than the species just discussed. It tends to be a more subdued orange in color, and the adult insect is found most often in August, September, and October (though stragglers can be out in November or even December). Here in Colorado I find this species commonly on flowers of rabbitbrush (Chrysothamnus or Ericameria depending on the botanical authority you consult).

Paradejeania rutilioides

This species goes by the common name of "Spiny Tachinid Fly" or "Hedgehog Fly," the latter epithet coined by fly expert and author Stephen A. Marshall. It has a similar distribution as A. vexatrix, divided geographically into two subspecies, one northern and one southern. The fly is a known parasite of caterpillars of Edwards' Glassy-wing, Hemihyalea edwardsii, a tiger moth in the family Erebidae (subfamily Arctiidae).

Tachinid flies in general are remarkable creatures that are of enormous benefit to us through their parasitic lifestyle. We would surely be overrun with pest caterpillars, stink bugs, and other insects were it not for the ability of tachinids to control pest populations. Further, they are important flower visitors that complement pollinators like bees.

Sources: Arnaud, Paul H., Jr. 1978. A Host-Parasite Catalog of North American Tachinidae (Diptera). Washington, DC: United States Department of Agriculture Miscellaneous Publication No. 1319. 860 pp.
O'Hara, James E. 2012. "Review of Tachinid Fly Diversity in the Gila National Forest, New Mexico," The New Mexico Botanist Special Issue No. 3: 32-41.
O'Hara, James. E. 2013. "Tachinidae Resources," North American Dipterists Society.
Young, Chen, et al. 2005. "Species Paradejeania rutilioides - Spiny Tachinid Fly," Bugguide.net.

Field Guide, Anyone?

The Christmas shopping season is fast approaching, and I would like to make your gift-giving decisions easier by offering signed copies of the Kaufman Field Guide to Insects of North America to you, my loyal followers, for a discount.

I am happy to write a personalized message in the book and send it to you for $16.00 U.S., plus shipping. This is a savings of nearly three dollars off the cover price of $18.95. Please place your requests by October 15 to insure ample time for me to order additional copies from the publisher, and ship the book(s) to you in time for you to deliver it to your family members, friends, students, yourselves, or other loved-ones for the holidays.

Please e-mail me with "Field Guide Order" in the subject line: BugEric24ATyahooDOTcom. I will keep you appraised of the timeline for receipt of the book(s) so you can know when to expect delivery. I can accept only checks for payment, please.

As always, I also greatly appreciate donations to keep this blog running; and I always welcome your requests for topics and other improvements to this site. Thank you!

Blue-winged Grasshopper

The band-winged grasshoppers in the subfamily Oedipodinae (family Acrididae) are easy to love. They are colorful and noisy in flight, seldom qualify as pests of agriculture or rangeland, and are endlessly diverse. A case in point is the beautiful Blue-winged Grasshopper, Trimerotropis cyaneipennis.

I first became acquainted with this species during childhood trips to eastern Oregon. They were fairly plentiful around Fort Rock in northern Lake County, but a real challenge to catch, even with a net. Nothing has changed, it took me several tries to net one that Heidi and I encountered in Water Canyon in the Magdalena Mountains of New Mexico last Sunday. I wanted to show Heidi, and my readers here, the blue-green hind wings that give this species its common name.

Like all members of the genus Trimerotrois, T. cyaneipennis is incredibly cryptic when at rest among rocks, or on bare soil. The front wings, called tegmina (singular is "tegmen"), are narrow and in this case speckled with brown, gray, and black, creating vague bands. The hind wings are used in flight, and fold like a Japanese fan, accordion-like, when not in use, concealed beneath the tegmina.

Even if you can follow the flight path of one of these insects, and note where it lands again, good luck spotting it unless it moves. Actually, it might even walk a short distance once it does land, making it even more maddening to locate.

The cloak of (near) invisibility works well, despite the fact that these are not small creatures. Adult males measure 25-35 millimeters, females 28-40 millimeters. Besides the blue hind wings, they can be identified in part by the bright blue tibia ("shin") segment of the hind leg, and the blue tint on the abdomen, visible in the image below.

This grasshopper is most common in rugged, mountainous terrain and canyons at elevations between 3,000 and, 8,500 feet. Look for them along gravel roads, and volcanic soils, especially at the base of steep slopes. They tend to favor oak, pinyon-juniper, or pine forests west of the Rocky Mountains from southeast Washington, Idaho, eastern Oregon, California, Nevada, Utah, southwest Colorado, Arizona, western New Mexico and extreme west Texas. They also range just across the Mexican border.

You might hear this grasshopper when it takes flight, as it generates a loud crackling sound as the veins of the hind wing rubs against the underneath surface of the tegmen. This is called "crepitation," and can be initiated at will by the insect, such that it can also fly silently.

There is continuing debate over the exact status of this species, and in southeast Wyoming, central Colorado, and much of eastern New Mexico, it is replaced by the closely-related "Brother's Band-winged Grasshopper," Trimerotropis fratercula. That species has yellow, or greenish-yellow hind wings, but even T. cyaneipennis does not always have obviously blue or turquoise wings.

Since this is more or less a "wilderness" grasshopper that does not eat crops or rangeland forage, it is not considered a pest. All the more reason to enjoy an encounter with this blue-winged beauty.

Sources: Bentley, Tom and David Ferguson. 2007. "Species Trimerotropis cyaneipennis - Blue-winged Grasshopper," Bugguide.net.
Capinera, John L., Ralph D. Scott, and Thomas J. Walker. 2004. Field Guide to Grasshoppers, Katydids, and Crickets of the United States. Ithaca: Comstock Publishing Associates (Cornell University Press). 249 pp.
Helfer, Jacques R. 1972. How to Know the Grasshoppers, Cockroaches and Their Allies (2nd Ed.). Dubuque, Iowa: Wm. C. Brown Company Publishers. 359 pp.

Hackberry Psyllids: A Fixture of Fall

Sometimes, it is easier to identify an insect by the evidence it creates than by seeing the bug itself. Such is the case with the abundant, but tiny, hackberry psyllids, genus Pachypsylla in the family Psyllidae and true bug order Hemiptera. Psyllids are also known as "jumping plant lice" for their resemblance to aphids and ability to vault themselves away from danger.

Along one of the streets that borders our townhouse complex in Colorado Springs are a pair of hackberry trees, among the few planted ornamentals that are not oak, maple, or elm. They are invariably exploited every summer by Pachypsylla celtidismama, which produces "nipple galls" on the underside of hackberry leaves. The small, tumor-like growths do not seem to affect the health of the tree in the least, but provide housing and food for the tiny insect within each one. Up to 52 galls have been found on a single leaf (Caldwell, 1938), and they vary from smooth in texture to rather hairy. Double and triple galls are not unheard of, but it is rare to find more than one nymph occupying each gall.

The adult stage of hackberry psyllids will start appearing shortly, if they are not emerging already. Adults of P. celtidismama are only 3.5-4.5 millimeters in length from "nose" to the tips of the folded wings. They resemble tiny cicadas, but can also be confused with barklice, order Psocodea. Barklice have chewing mouthparts, though, while psyllids in general have beak-like piercing-sucking mouthparts they use to tap plant sap.

Hackberry psyllids make themselves a real nuisance when they start seeking nooks and crannies in which to hibernate. They can gather by the dozens, if not hundreds, on the exterior of doors, window screens, and the siding of homes. They pose no threat, of course, and simply hosing down the masses with water will solve the problem. The appearance of these insects en masse is a brief affair anyway.

A different Pachypsylla species

Next spring, female psyllids will deposit eggs on the leaves of hackberries at the precise time when the leaves begin unfolding from the bud. Should a psyllid deposit her eggs too early, or too late, and the chances of successful development of her offspring plunges dramatically.

The formation of the bulging gall is the tree's response to the feeding of the nymph that hatches from the egg. The little dome-like pocket insulates the nymph from hostile abiotic environmental factors, and protects it from at least some predators and parasites. The nymph goes through five stages, the last instar illustrated in the images below. Note the two pairs of developing wing pads. The spike-like projections on the rear of the insect will help it to cut an exit in the gall before it emerges as an adult.

Nymph of P. celtidismama © Hannah Nendick-Mason via Bugguide.net

Nymph of P. celtidismama © Hannah Nendick-Mason via Bugguide.net

Despite their seemingly impenetrable fortress, the nymphs are still vulnerable to tiny parasitic wasps, including Psyllaephagus spp. (family Encyrtidae), and Torymus spp. (family Torymidae). The larval wasps feed as parasites on the nymphs and then chew their way out of the gall once they complete development.

Psyllaephagus sp. © John Rosenfeld via Bugguide.net

This, and the other six species of hackberry psyllids, range pretty much wherever hackberry occurs naturally, and increasingly where it is used as an ornamental tree. The different species of psyllids make correspondingly different styles of galls, so it is easiest to assess the gall shape, size, and location to determine which psyllid is responsible. Keep in mind that gall midges (family Cecidomyiidae) can also create galls on hackberry.

You might try rearing a few galls to see what parasites emerge along with the adult psyllids. It is entirely possible you could record a new host record in the process.

Sources: Berenbaum, May R. 1989. Ninety-nine Gnats, Nits, and Nibblers. Urbana: University of Illinois Press. 263 pp.
Caldwell, John S. 1938. "The Jumping Plant-lice of Ohio," Ohio Biological Survey Bulletin 34, vol. VI, No. 5: 229-281.
Winterringer, Glen S. 1961. "Some Plant Galls of Illilnois," Story of Illinois Series No. 12. Urbana: Illinois State Museum. 51 pp.