Thursday 17 December 2015

Possible Wasp-mimcry in a Mexican Hangingfly.

Hangingflies, Bittacidae, are highly specialized Scorpionflies, Mecoptera, noted for their resemblance to Crane Flies (which are True Flies, Diptera, and only have a single pair of wings) and their tendency to hang upside down in wait for prey. Like other Scorpionflies they are a rellict group today, with only about 170 species known worldwide (and most of those extremely rare), but were an important part of Insect faunas in the Jurassic, before Angiosperms (Flowering Plants) and associated Insects came to dominate terrestrial ecosystems.

The genus Eremobittacus is known from two species, Eremobittacus spinulatus and Eremobittacus sodalium, both of which are known from single male specimens from Mexico. To date attempts to find further specimens of either species, particularly females and juveniles, have proved futile, despite some extensive searches in the areas from which they were first described.

In a paper published in the journal ZooKeys on 23 November 2015, Fernando Villagomez of the Laboratorio de Ecología y Sistemática de Microartrópodos at the Universidad Nacional Autónoma de México, Atilano Contreras-Ramos of the Departamento de Zoología at the Universidad Nacional Autónoma de México and Yesenia Marquez-López of the Maestría en Biología at the Universidad Autónoma Metropolitana-Iztapalapa describe a series of specimens of Eremobittacus spinulatus discovered in the collection of the National Collection of Insects of the Institute of Biology of the Universidad Nacional Autónoma de México. 

The series comprises six specimens, three male and three female, that were collected in Oaxaca State in 1998, close to the area where the species was discovered in 1997 and in an area where further specimens were being actively sought, though they were apparently not recognized at the time (this is not as surprising as it sounds; Hangingflies are rare insects that most entomologists are unlikely to be familiar with, and the original description of Eremobittacus spinulatus was published in an American journal in English, before it was possible to search journals quickly online).

Eremobittacus spinulatus (1) male and (2) female. Villagomez et al. (2015).

The specimens show marked sexual dimorphism, with enlarged upper hind legs on the males, which is very unusual in Hangingflies. In addition the species is extremely Wasp-like in appearance, which could possibly be an indicator of mimicry in the species. Although predatory themselves, Hangingflies are subject to predation by a variety of other animals, including Spiders, Damselflies, Robber Flies and Assassin Bugs, against which they have few defenses. This would make resembling a Wasp highly advantageous, as Wasps have powerful stings, strong mandibles and are generally aggressive, so that many predators tend to avoid them. However in order for such mimicry to be effective it would be necessary for the Hangingfly to exhibit Wasp-like behavior, such as actively foraging for prey, rather than hanging upside down in wait. Such behavior is known in some Hangingflies, so it is a possibility for Eremobittacus spinulatus, though observation of living specimens would be needed before this could be confirmed.

See also... new species of Hangingflies from the Middle Jurassic of Inner Mongolia.       Hangingflies, Bittacidae, are large members of the Scorpionfly order, Mecoptera, which resemble the more widespread Craneflies (members of the True Fly order, Diptera) both in morphology and lifestyle, although...
Hangingflies are long legged Scorpionflies (Mecoptera), a group of insects related to the True Flies. Scorpionflies get their name from the reproductive organs of the males of some species, which resemble the tails of Scorpions. Despite this fierce appearance most species are harmless herbivores, though it is thought that fleas are highly...
Earwigflies (Meropeidae) are a small group within the Mecoptera (Scorpionflies), known only from four fossil and two modern species. Three of the fossil species are from the Triassic of Kyrgyzstan, and the fourth from the Jurassic of Siberia, while the two modern species, Merope tuber and Austromerope poultoni are from North America and Australia respectively. Little is known of the biology of these Insects, the larvae having never...

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