The Robber Flies of Crowley's Ridge, ArkansasAn Illustrated Field Guide by Norman Lavers |
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An Illustrated Field Guide
Introduction
What is Crowley's Ridge?
What is a Robber Fly?
Appendices:
Bibliography
Distribution and Flight Period
Spotting Robber Flies
Subfamily: Leptogastrinae
Leptogaster atridorsalis
Leptogaster brevicornis
Leptogaster flavipes
Leptogaster virgata
Tipulogaster glabrata
Subfamily: Dasypogoninae
Diogmites angustipennis
Diogmites misellus
Diogmites neoternatus
Diogmites missouriensis
Diogmites texanus
Diogmites platypterus
Diogmites discolor
Nicocles pictus
Subfamily: Laphriinae
Atomosia puella
Atomosia melanopogon
Atomosia rufipes
Atomosia sayii
Cerotainia macrocera
Cerotainia albipilosa
Orthogonis stygia
Lampria bicolor
Lampria rubriventris
Laphria flavicollis
Laphria grossa
Laphria lata
Laphria macquarti
Laphria thoracica
Laphria sicula
Laphria index
Laphria cinerea
Laphria affinis
Subfamily: Laphystiinae
Laphystia ochreifrons
Psilocurus birdi
Psilocurus nudiusculus
Subfamily: Stenopogoninae
Heteropogon macerinus
Holopogon phaeonotus
Ceraturgus elizabethae
Echthodopa formosa
Prolepsis tristis
Subfamily: Stichopogoninae
Stichopogon trifasciatus
Townsendia nigra
Subfamily: Trigonomiminae
Holcocephala fusca
Subfamily: Apocleinae
Efferia (Nerax) aestuans
Efferia (Albibarbefferia) albibarbus
Efferia (Pogoniefferia) nemoralis
Efferia (Pogoniefferia) plena
Efferia (Pogoniefferia) prairiensis
Efferia (Pogoniefferia) pogonias
Triorla interrupta
Mallophora orcina
Proctacanthus duryi
Proctacanthus hinei
Proctacanthus milbertii
Proctacanthus nigriventris
Promachus bastardii
Promachus fitchii
Promachus hinei
Subfamily: Asilinae
Asilus sericeus
Dicropaltum rubicundus
Neoitamus flavofemoratus
Philonicus rufipennis
Machimus Erythocnemius
Machimus snowii
Machimus virginicus
Machimus maneei
Neomochtherus auricomus
Subfamily: Ommatiinae
Ommatius ouachitensis
Ommatius gemma
Other Sites:
Other Arkansas Robber Flies
Apachekolos tenuipes
Leptogaster murina
Psilonyx annulatus
Laphria saffrana
Laphria vorax
Eudioctria tibialis
Microstylum morosum
Hadrokolos texanus
Lasiopogon oklahomensis
Holcocephala calva
Megaphorus acrus
Proctacanthus rufus
Machimus sadyates
Machimus antimachus
Other PicasaWeb Albums
Recent Crowley's Ridge Robber Fly updates
The Tiger Beetles of Crowley's Ridge
101 Butterflies of Crowley's Ridge
Swallowtails
Pierids
Lycaenids
Nymphalids
Spreadwing Skippers
Grass Skippers
Other Arkansas Butterflies
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When my friend Herschel Raney (see his much fuller website at www.hr-rna.com/RNA/index.htm) and I began studying Robber Flies in Arkansas about six years ago, all we knew is what was, and what wasn't, a Robber Fly. We acquired a Key to the Genera of North American robbers, and we had to catch each new fly we saw, key it to Genus, find a paper that discussed that Genus and contained a Key to the Species, and send for the paper, and key it out. At the end of each season we donated all our specimens to the Arthropod Museum at the University of Arkansas, and the curator, Jeff Barnes, checked our ID's and corrected our mistakes. But little by little we used our birdwatching skills to find field marks for each species, so that we could identify it in the field without having to catch it. Now we can identify almost every species we see, unless it is something new. It is those field marks I will try to convey here. All photographs here are by Norman Lavers or Cheryl Lavers. Rather than using idealized portraits, we have tried to select the images which looked most like the way species appeared in the field. Although our focus of study is a small area of northeastern Arkansas, in fact the majority of species here are found throughout Arkansas and adjacent areas of Oklahoma, Missouri, Tennessee, and Louisiana. We have now begun, as an appendix, "Other Arkansas Robber Flies," which ultimately will include every species of Robber Fly anyone is likely to see in the state as a whole, and most of those likely in the region. So far as I know, this is the first attempt by anyone to create a guide to the identification of Robber Flies in the field. Since I am learning how to do this as I go, I would appreciate corrections for any mistakes I have made; hearing about additional field marks that I have missed; and especially I would like to know if this guide is useful in helping you to identify Robber Flies. What I really want is to make you aware of these fearless and fascinating predators that are all around you, though you may never have noticed them before. This website has been created by Gawain Lavers. > What is Crowley's Ridge?Crowley's Ridge is an anomalous feature rising out of the otherwise flat Mississippi Delta in northeast Arkansas. It is possibly a unique feature in the world, tilted up by an earthquake in the late Cretaceous, when the area was at the bottom of an inland sea. The 1811-1812 New Madrid earthquakes show this is still a region of puzzling seismic activity, despite being far from any plate boundaries. The area is considered a "failed rift" where the continent thought about dividing, then changed its mind. Crowley's Ridge begins at the Missouri border in the northeast corner of Arkansas and runs south for 150 miles, bisecting parts of eight counties, before it meets the westward-trending Mississippi River. It is nowhere more than a few hundred feet high, or a few miles wide. The soft and highly erodible loess soil has helped create a landscape of high ridge trails and steep-sided deep ravines. The Ridge, an island in the Delta, long isolated from other highlands, and relatively undisturbed by agriculture and the periodic flooding of the bottom lands, has its own distinct botany, including many relict species, and this extends to some insect species as well. My wife Cheryl and I have been studying Robber Flies (Family: Asilidae) here since 2003 and so far have recorded 66 species. Another 2 species have been recorded in the literature. These flies are primary predators in their own ecosystems. I would like to present here an illustrated field guide to these fierce and rather charismatic creatures. [back to the top] What is a Robber Fly?Here is a typical Robber Fly, showing general features. Note the eyes set wide apart for good depth perception, with even a depression between the eyes to allow full sweeping vision. Also characteristic is the more or less hairy face (the "mystax"), which, it is theorized, protects the eyes during battles with large and dangerous prey. Now note the high arching thorax containing the powerful muscles which activate the wings, allowing it to fly up in an instant and snatch fast-flying prey out of the air. Robbers (unlike many similar appearing flies in other families) normally land with their wings folded together over the back of their extended abdomens, and this will help you pick them out. Note the long spiky muscular legs with which they capture and hold their prey (see especially the falcon-like talons at the ends of their legs). Hidden beneath the mystax (in this picture) and no doubt stabbed into the head of this hapless bee is a sharp beak backed by neurotoxins and digestive juices, which allow it to kill its prey (very often bees or wasps) quickly, and suck their juices out, like the tiny (often green-eyed) draculas that they are. No wonder entomologists are fond of them! Robbers are in the Order Diptera, the true flies, characterized by having two wings (instead of the four wings typical of other orders). For engineering reasons I don't understand, two wings are much more efficient than four wings, and flies are the champion flyers of the insect world. Their hind wings have been reduced to little balancing organs (the halteres), which you can see on this fly as yellow knobs down below the wing bases. While I was taking a picture of that small robber, it flew up so swiftly it seemed to vanish. An instant later it was back, carrying the flying termite it had just snatched out of the air. [back to the top] First Subfamily: Leptogastrinae |
All images and text copyright © Norman Lavers 2007If you have questions or comments please email comments173@normanlavers.net |