T.G.I.Flyday

T.G.I.Flyday: Soybean nodule fly

/ Ted C. MacRae / 3 Comments

I’ve been walking the rows of soybean fields for many years now, and while it might seem that I would have very quickly seen all there was to see in terms of insects associated with the crop, this is not the case. The major players are almost always present—lepidopteran caterpillars such as velvetbean caterpillar (Anticarsia gemmatalis) and soybean looper (Chrysodeixis includens), and stink bugs such as southern green stink bug (Nezara viridula), red-banded stink bug (Piezodorus guildinii) and brown stink bugs (Euschistus spp.). However, numerous other insects can be found at one time or another—some of great importance from the perspective of the farmer producer but others with very little impact on the crop. During a tour of soybean fields in Mississippi this past September, I saw a large number of “signal flies”¹ (family Platystomatidae) on the foliage of the soybean plants that I presumed to represent the soybean nodule fly, Rivellia quadrifasciata.²

¹ I originally learned these to be “picture-winged flies”—a name now more commonly used to refer to members of the family Ulidiidae—which I learned as “Otitidae”!

² This species can be separated with certainty from the closely related and largely sympatric species R. colei only by examination of male genitalia (Namba 1956). Rivellia quadrifasciata is more common and widespread than R. colei and is the species cited in literature in association with soybean.

Rivellia quadrifasciata (soybean nodule fly) | Stoneville, Mississipi

Rivellia quadrifasciata (soybean nodule fly) | Stoneville, Mississipi

Rivellia quadrifasciata is widely distributed in the eastern U.S. where it originally fed probably on tick trefoil, Desmodium spp. (Foote et al. 1987), but has since adapted to soybean, Glycines max (Eastman & Wuensche 1977), and black locust, Robinia pseudoacacia (McMichael et al. 1990). Despite its relatively recent adaptation to soybean as a favored host plant, the species does not appear to cause much economic damage to the crop. The small, white, maggot-like larvae live in the soil and feed on the Rhizobium nodules of the roots that are used by the plant for nitrogen-fixation. Soybean, of course, is famous for its compensatory abilities and can withstand considerable nodule injury without yield impact, and as a result losses from this insect are considered minor (Heatherly & Hodges 1998).

Signal flies wave their wings constantly.

The wings of signal flies are almost always in constant motion.

Of more interest from a natural history perspective, these flies—like other members of the Platystomatidae—are almost always seen with their wings in a constant “waving” motion as they walk about on the host leaves. This seems clearly an intraspecific “signaling” behavior (and the source of the family’s common name), with the pattern of markings on the wings and the particular sequence of movements of the wings combining to provide species-specific signals for mate recruitment. Some Asian members of the family are famous for the remarkably elongated eye stalks of the males, which aid in intraspecific male-to-male combat behaviors that provide selection pressure for even more elongate eye stalks. Sadly, our North American species exhibit no such modifications of the head, but their strangely tubular mouthparts do give them the appearance of wearing a “gas mask.”

gas mask

The strangely tubular mouthparts give adults the appearance of wearing a “gas mask.”

Information on the biology of adult platystomatids is limited, but a wide range of adult foods, e.g. nectar, honeydew, plant sap, bird droppings, and carrion, have been reported for this species, and R. quadrifasciata males have been observed to feed females globules of liquid during mating.

REFERENCES:

Eastman, C. E. & A. L. Wuensche. 1977. A new insect damaging nodule of soybeans: Rivellia quadrifasciata (Macquarl). Journal of the Georgia Entomological Society 12:190–199.

Foote, B. A., B. D. Bowker & B. A. McMichael. 1987. Host plants for North American species of Rivellia (Diptera, Platystomatidae). Entomological News 98:135–139 [Biodiversity Heritage].

Heatherly & Hodges. 1998. Soybean Production in the Midsouth. CRC Press LLC, Boca Raton, Florida, 416 pp. [Google Books].

McMichael,  B. A., B. A. Foote & B. D. Bowker, B. D. 1990. Biology of Rivellia melliginis (Diptera: Platystomatidae), a consumer of the nitrogen-fixing root nodules of black locust (Leguminosae). Annals of the Entomological Society of America 83(5):967–974 [abstract].

Namba, R. 1956. A revision of the flies of the genus Rivellia (Otitidae, Diptera) of America north of Mexico. Proceedings of the U.S. National Museum 106:21–84 [Biodiversity Heritage].

Copyright Ted C. MacRae 2013

T.G.I.Flyday—fuzzy wuzzy wuz a…

/ Ted C. MacRae / 4 Comments
Megaphora? sp. | Lyon Co., Nevada

Megaphora? sp. | Lyon Co., Nevada

I’m back after an uncharacteristically lengthy absence, due not to loss of desire or inspiration but rather a malfunctioning computer. Repeated attempts to restore connectivity were unsuccessful, and heavy travel during the past week only exacerbated the situation. However, all is well now (for the time being—hopefully a new machine will arrive before my current one bites the dust), and as a peace offering until I can post something more substantial I offer this photo of a robber fly (family Asilidae) that I photographed near Wellington Springs in Lyon Co., Nevada during my late August Great Basin collecting trip. The fly was found very much alive but torpidly clinging to the stem of Chrysothamnus viscidiflorus (yellow rabbitbrush). My best guess is something in the genus Megaphorus (correction or confirmation by any passing fly guys would be much appreciated).

Speaking of my Great Basin collecting trip, I’m putting together an “iReport” of the trip featuring a general synopsis and photographs taken exclusively with my iPhone. Don’t snicker—when used within its capabilities an iPhone can take quite good photographs. I carry mine with me at all times despite also carrying a “real” camera and use it in situations that play to its strengths and don’t require the big camera. At any rate, look for something in the next day or so.

Copyright © Ted C. MacRae 2013

T.G.I.Flyday – Andrenosoma fulvicaudum

/ Ted C. MacRae / 19 Comments

Andrenosoma fulvicaudum | Stone Co., Arkansas

First, about the name. T.G.I.Flyday is my contribution to a collusional triad between dipterist Morgan Jackson, myrmecologist Alex Wild, and myself (uhm, beetles).  Although Alex blogs primarily about ants, he has long featured a “Friday Beetle Blogging” series.  I’ve also occasionally stepped on their toes with an ant or fly post, so Morgan and I thought it would be fun to complete the Friday switcheroo with a post about ants on his blog and one about flies on mine. Get it?… Oh well, it made me chuckle when we thought it up.  Anyway, here is my first T.G.I.Flyday contribution.

Among the flies (order Diptera), it is hard to pick anything but robber flies (family Asilidae) as the most charismatic group.  Several subfamilies of robber flies have candidates that vie for the most impressive species, mostly due to their enormous size combined with striking green eyes (e.g., Microstylum morosum, Diogmites neoternatus) or vivid, aposematic / mimetic coloration (e.g., Archilestris magnificus, Eccritosia zamon, Wyliea mydas).  However, my favorite subfamily is the Laphriinae—not because of the amazing bumble bee-like appearance of the nominate genus, but rather the larval food of all species in the subfamily; wood-boring beetle larvae.  Over the years, I have put up hundreds of batches of dead wood for rearing wood-boring beetles in the families Buprestidae and Cerambycidae, and not uncommonly do I find in one of the emergence containers—especially those containing dead pine—an adult of one of these impressive flies. Oftentimes their characteristic pupal cases will be found protruding from the emergence hole, in which case I pin it underneath the fly (just in case some ambitious dipterist examines my collection after I’m gone and finds that the pupal case of xx species is not yet described).  I’ve by now accumulated a rather decent little robber fly collection (especially considering that I’m really a coleopterist), graciously identified for the most part by world robber fly expert Dr. Eric Fisher (California Department of Food and Agriculture).

Last weekend I made the second in a series of trips I’ll be taking to the White River Hills region of north-central Arkansas in an effort to confirm the occurrence there of Cylindera celeripes (swift tiger beetle).  My efforts are focused on the area around Calico Rock, a marvelous system of acidic sandstone barrens interspersed amongst shortleaf pine and oak forests.  The occasional dead pines found in such areas are highly attractive to a variety of pine-associated buprestids and cerambycids (my first loves), and whenever I see a standing dead tree I make a beeline straight for it (the tiger beetles can wait).

This individual was sitting on the trunk of a dead shortleaf pine with a mirid bug for prey.

On this day, sitting on the trunk of the first dead pine that I approached was not a buprestid or cerambycid, but rather this laphriine robber fly.  Based on the reddish posteriodorsal markings of the abdomen and general gestalt, I take this to be Andrenosoma fulvicaudum, a widespread though never very abundant species that occurs across most of North America.  According to Bromley (1934), the species frequents dry, sandy locations where it rests on logs, stumps, or tree trunks exposed to the bright sunlight and is commonly observed preying on small hymenopterans.  These observations are quite consistent with mine, except this one was feeding on a true bug in the family Miridae (perhaps distracting it just enough to allow me these photographs).  Cannings (1998) notes that A. fulvicaudum is attracted to recently burned forests, which will provide a fresh supply of wood-boring beetle larvae on which its larvae can prey.  This is the only species of Andrenosoma occurring in eastern North America; four additional species are restricted to Texas and a fifth occurs only in the western U.S., but the genus reaches its greatest diversity in the Neotropics.

REFERENCES:

Bromley, S. W. 1934. The Laphriine Robber Flies of North America.  Ph.D. dissertation, Ohio State University, 358 pp.

Cannings, R. A. 1998. Robber flies (Insecta: Diptera: Asilidae), In I. M. Smith and G. G. E. Scudder [Eds.], Assessment of Species Diversity in the Montane Cordillera Ecozone, Burlington: Ecological Monitoring and Assessment Network.

Copyright © Ted C. MacRae 2011