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Diogmites

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Diogmites

Diogmites
a male of Diogmites angustipennis from eastern New Mexico
Scientific classification
Kingdom:
Animalia
Phylum:
Arthropoda
Class:
Insecta
Order:
Diptera
Suborder:
Brachycera
Superfamily:
Asiloidea
Family:
Asilidae
Subfamily:
Dasypogoninae
Genus:
Diogmites

Loew, 1866
Type species
Diogmites platypterus
Loew, 1866
Species

over 70, see text

Synonyms

none

Diogmites is an insect genus of mainly neotropical Diptera in the family Asilidae or robber flies.

Description

Medium to large-sized robber flies (17-48 mm) with mostly minute body hair, thoracal bristles are mostly confined to a row on the mesonotum and two bristles on the scutellum. The mystax is of relatively modest size and is made up of comparatively few bristles, which do not or barely overlap the beak in side view. The antennae have a relatively slender third article that forms over half of the antennal length and carries a single, minute apical hair. Face narrower than the width of one eye. Abdomen slender and sometimes slightly constricted, its posterior end reaches or extends past the wing tips. Wings are usually clear or only slightly tinted. Body coloration predominantly straw-yellowish to orange-reddish, in some species darker brown to black. Eye coloration of live animals often includes iridescent green.

Legs comparatively long with prominent bristles, the length of the hind legs often roughly equals the length of the entire body. Forelegs about two-thirds as long as hind legs, with a short but distinctive curved spine at the anterior edge of each tibia. The claws of the hind legs are less than twice as long as the pulvilli. As is typical for Dasypogoninae, the harder cuticle of the prosternum is separated from the neck by an area of flexible membrane that presumably allows for greater freedom of movement of the forelegs. It should be noted however that this feature also occurs in some members of other asilid subfamilies.[1]

As with most asilids, known pupae of Diogmites species have prominent tooth- or hook-like anterior protrusions technically referred to as antennal processes. In this particular genus they include an undivided pair of anterior antennal processes without any basal bristles, and three posterior antennal processes[2][3]

Ventral view of the prothorax in Diogmites angustipennis showing the reduced prosternum typical of the subfamily Dasypogoninae
Front view of Diogmites angustipennis with claw-like spine at end of first tibia, a character typical for the genus. Another useful identifying character is the narrow face that is clearly less wide than each eye.
Hanging Thief - Diogmites properans from Okeefenokee Swamp National Wildlife Refuge, showing the tibial spine and narrow face typical for the genus

Biology

Adults of Diogmites species hunt as ambush predators, taking off from a resting position on the ground or on branches to intercept other flying insects, or to pounce on perching/crawling prey. After prey capture, these robberflies will then land to feed in a very characteristic posture that has earned this genus the common name of Hanging Thieves: they will hang from plant stems or leaves suspended by one or both front legs , with the other legs holding and manipulating the prey while feeding. Presumably the relatively long legs and reduced prosternum of the genus are part of adaptations to facilitate feeding during this suspended posture.

Hanging thieves should not to be confused with predatory scorpionflies of the family Bittacidae which are commonly called Hangingflies and which actually capture flying prey in a suspended posture.

Many observations of the suspended feeding posture of Diogmites were caught on camera, for example Herschel Raney's webpage for Dasypogoninae includes images of D. angustipennis, D. platypterus and D. missouriensis feeding on a variety of insects while hanging from plant leaves or stalks with one or both forelegs [4]. Chris Thawley has an interesting video of a feeding adult manipulating its prey while in hanging posture[5]. Observations of the moment of prey capture are unfortunately not recorded yet in any literature or web resources. Some species can assume an unusual flight posture, with the first and last leg pairs raised high while the middle legs are extended downwards (personal observation of low-flying D. angustipennis males and females in central New Mexico). This might represent a peculiar type of hunting-related behavior more commonly referred to as orientation flights, or perhaps might serve purposes unrelated to hunting, such as a defensive posture to reduce odds of capture by dragonflies or other robberflies, or behavior intended to facilitate latching onto plant stems and leaves for landing.

Diogmites species take prey from an extremely wide range of winged insect orders: Robert Lavigne's Predator-Prey Database for the family Asilidae[6] has 443 records of observations for at least 20 species Diogmites feeding on a wide range of prey, including other asilids as well as dragonflies. Particular species can display narrower prey choice however, for example D. crudelis was observed to feed on Diptera or Hymenoptera in 89 of 93 cases[7]. Very little is known about larval biology, but D. misellus and D. neoternatus larvae were respectively observed and surmised to feed on scarabaeid grubs[2]. Larvae appear to live and pupate in soil, adults apparently emerge after the pupae work their way up through the soil surface until the anterior half of the body protrudes. Whitney Cranshaw has captured emergence of an adult D. angustipennis in a series of remarkable photographs available at Zipcodezoo[8]. Norman Lavers' Illustrated Field Guide to The Robber Flies of Crowley's Ridge, Arkansas details egg-laying behavior of D. platypterus and includes a more detailed photo of a protruding pupal cuticle[9].

Diogmites properans (?) demonstrating the suspended feeding posture of a typical Hanging Thief
Compare and contrast: this looks like Diogmites but is actually an extra large Caenarolia species from central Argentina. Note absence of the tibial spur on forelegs and complete absence of pulvilli below the elongated tarsal claws.

Taxonomy

Depending on the source, 73 to 77 species are currently recognized in Diogmites:[10][11]


Phylogeny

Although Diogmites is usually considered a member of the subfamily Dasypogoninae, combined analysis of morphological and molecular characters places Diogmites tristis in a clade corresponding to the subfamily Stenopogoninae instead, without however providing direct support for monophyly of this subfamily[15].

References

  1. ^ http://www.biodiversitylibrary.org/part/65788 Artigas, J.N. & Papavero, N. (1988): The American genera of Asilidae (Diptera): Keys for identification with an atlas of female spermathecae and other morphological details. II. Key to the genera of Dasypogoninae Macquart, with descriptions of new genera and species and new synonymies. - Gayana. Zoologia. Universidad de Concepcion, Instituto Central de Biologia 52(3-4): 199-260; Concepcion.
  2. ^ a b http://www.mapress.com/zootaxa/2008/f/zt01868p098.pdf Dennis, D.S. 2008. Pupal cases of nearctic robber flies (Diptera : Asilidae). Zootaxa 1868: 1-98.
  3. ^ http://www.bioone.org/doi/full/10.3956/2013-15.1 Dennis, D.S. & Barnes, J.K. 2013. The pupal case of a Nearctic robber fly, Diogmites contortus Bromley 1936 (Diptera: Asilidae). Pan-Pacific Entomologist 89: 168-175.
  4. ^ http://www.hr-rna.com/RNA/Main%20pages/Diogmites%20frame%20page.htm
  5. ^ https://thelizardlog.wordpress.com/2013/09/04/hanging-thieves/
  6. ^ http://www.geller-grimm.de/catalog/lavigne.htm Predator-Prey Database for the family Asilidae
  7. ^ http://eds.a.ebscohost.com/eds/detail/detail?vid=0&sid=d9fe38ec-8014-4e1d-895e-0096a62eeb94%40sessionmgr4008 Dennis, D.S. 2015. Ethology of Diogmites crudelis Bromley, 1936 (Diptera: Asilidae) in Northeastern Florida, U.S.A. J. Entomol. Res. Soc. 17: 23-44.
  8. ^ http://zipcodezoo.com/index.php/Diogmites_angustipennis#mediadiv
  9. ^ http://normanlavers.net/dasypogoninae.php
  10. ^ a b c d http://www.geller-grimm.de/catalog/species.htm
  11. ^ a b c d http://www.gbif.org/species/1662345
  12. ^ Carrera, M. 1949. Contribuição ao conhecimento dos Asilidae neotropicais (Diptera). I. Sôbre as espécies brasileiras com esporão no tíbia. Arquivos de Zoologia 7/2:1–148.
  13. ^ http://revistas.ffclrp.usp.br/Neotropical_Diptera/article/view/209 Papavero, N. 2009. Catalogue of Neotropical Diptera. Asilidae. Neotropical Diptera 17: 1-178.
  14. ^ http://www.mapress.com/zootaxa/2014/f/z03861p126f.pdf Alvim, E., Ale-Rocha, R. & Bravo, F. 2014. Taxonomic revision of Neodiogmites Carrera, 1949 (Diptera, Asilidae) and description of two new species, Zootaxa 3861, 101-126.
  15. ^ http://www.sciencedirect.com/science/article/pii/S1439609209000087 Dikow T. 2009. A phylogenetic hypothesis for Asilidae based on a total evidence analysis of morphological and DNA sequence data (Insecta: Diptera: Brachycera: Asiloidea). Organisms Diversity & Evolution, 9(3): 165-188.


Asilidae

Sandbox drafting completed for one of the more complex and diverse robberfly genera

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