The
Brachycera
The Brachycera are a suborder of the order Diptera. It is a major suborder consisting of around 120 families. Their most distinguishing characteristic is reduced antenna segmentation.
Description
A summary of the main physical characteristics i ...
n family Vermileonidae (the sole family in the infraorder Vermileonomorpha) is a small family of uncertain affinities and unusual biology. It includes fewer than 80 described species, most of them rare and with restricted distribution, in 10 genera. Historically the vermileonids had been regarded as belonging to the family
Rhagionidae
Rhagionidae or snipe flies are a small family of flies.
They get their name from the similarity of their often prominent proboscis that looks like the beak of a snipe.
Description
Rhagionidae are medium-sized to large flies with slender bodies a ...
, possibly in a subfamily Vermileoninae. Their biology and morphology are so markedly distinct from the main Rhagionidae ''
sensu
''Sensu'' is a Latin word meaning "in the sense of". It is used in a number of fields including biology, geology, linguistics, semiotics, and law. Commonly it refers to how strictly or loosely an expression is used in describing any particular co ...
stricto'' however, that the placement as a separate family has been widely accepted.
Adult
The adults are slender, fragile, long-legged flies, vaguely reminiscent of small
crane flies
Crane fly is a common name referring to any member of the insect family Tipulidae. Cylindrotominae, Limoniinae, and Pediciinae have been ranked as subfamilies of Tipulidae by most authors, though occasionally elevated to family rank. In the most ...
. The adults generally visit flowers for nectar, but adults of some species may not feed at all. The mouthparts of the adult are
hypognathous
This glossary of entomology describes terms used in the formal study of insect species by entomologists.
A–C
A synthetic chlorinated hydrocarbon insecticide, toxic to vertebrates. Though ...
, used mainly for extracting nectar from flowers, long, and straight. This might have something to do with the common name "snipe-fly" for the family
Rhagionidae
Rhagionidae or snipe flies are a small family of flies.
They get their name from the similarity of their often prominent proboscis that looks like the beak of a snipe.
Description
Rhagionidae are medium-sized to large flies with slender bodies a ...
, but it would be misleading to use that name for Vermileonidae now, as they are no longer included in the Rhagionidae, which still are called snipe-flies.
Most vermileonid species are found in the drier regions of the western parts of Africa, from the Cape to Morocco, and also in the western parts of the Iberian Peninsula, mainly in Portugal.
Larvae
![Leptynoma sericea 2508s](https://upload.wikimedia.org/wikipedia/commons/b/bb/Leptynoma_sericea_2508s.JPG)
The
larva
A larva (; plural larvae ) is a distinct juvenile form many animals undergo before metamorphosis into adults. Animals with indirect development such as insects, amphibians, or cnidarians typically have a larval phase of their life cycle.
The ...
e of vermileonids are called wormlions which amounts to a direct translation of ''Vermileo''. They have evolved the same elaborate mechanism for trapping prey, as one sees in many species of the
Neuroptera
The insect order Neuroptera, or net-winged insects, includes the lacewings, mantidflies, antlions, and their relatives. The order consists of some 6,000 species. Neuroptera can be grouped together with the Megaloptera and Raphidioptera in th ...
n family
Myrmeleontidae
The antlions are a group of about 2,000 species of insect in the neuropteran family Myrmeleontidae. They are known for the predatory habits of their larvae, which mostly dig pits to trap passing ants or other prey. In North America, the larvae ...
, the so-called "
antlions
The antlions are a group of about 2,000 species of insect in the neuropteran family Myrmeleontidae. They are known for the predatory habits of their larvae, which mostly dig pits to trap passing ants or other prey. In North America, the larvae ...
"; that is, they make cone-shaped "pits" in sandy areas and feed on insects that fall into the pits. The mechanism is elegant in that in both groups of insects, the larva creates the pit by flinging particles out. Much of the material falls back, coming to rest at effectively the critical
angle of repose
The angle of repose, or critical angle of repose, of a granular material is the steepest angle of descent or dip relative to the horizontal plane to which a material can be piled without slumping. At this angle, the material on the slope fac ...
. This is a good example for
convergent evolution
Convergent evolution is the independent evolution of similar features in species of different periods or epochs in time. Convergent evolution creates analogous structures that have similar form or function but were not present in the last com ...
.
Thus, when a small insect, commonly an ant, blunders into the pit, its weight causes the sand to collapse below it, drawing the victim toward the center, where the larva lies in wait under a thin layer of loose sand. As soon as it is alerted by falling sand grains, the larva assists this process by vigorously flicking more sand out from the center of the pit. This undermines the pit walls and causes them to collapse toward the center. The sand that the larva now is flinging also pelts the prey with so much loose, rolling material as to prevent it from getting any foothold on the easier slopes that the initial collapse of the slope has presented. The combined effect is to bring the prey down to within grasp of the larva, which then can inject venom and digestive fluids.
Unlike the pit-digging
Myrmeleontidae
The antlions are a group of about 2,000 species of insect in the neuropteran family Myrmeleontidae. They are known for the predatory habits of their larvae, which mostly dig pits to trap passing ants or other prey. In North America, the larvae ...
, vermileonid larvae do not travel round and round while digging the pit trap. Instead, they simply lie at the centre with the rear end buried, and dig their heads repeatedly forward into the sand, flinging it out by vigorously straightening their fore ends. In contrast with conical digging, this approach is believed to take longer since more sand is likely to fall back into the pit when throwing from the center. Finally, they cover themselves with a thin layer of sand while lying across the bottom of the cone. Wormlion larvae prefer shaded habitats over lit ones, fine sand of small particle size over coarser sand, and obstacle free soil.
All these factors enable them to construct large pits. Unfavorable conditions lead to more frequent relocation of the pits.
The main enemies of the larvae of either antlions or wormlions are ground-hunting birds such as
hoopoe
Hoopoes () are colourful birds found across Africa, Asia, and Europe, notable for their distinctive "crown" of feathers. Three living and one extinct species are recognized, though for many years all of the extant species were lumped as a single ...
s and
gallinaceous birds
Galliformes is an order of heavy-bodied ground-feeding birds that includes turkeys, chickens, quail, and other landfowl. Gallinaceous birds, as they are called, are important in their ecosystems as seed dispersers and predators, and are often ...
that learn to recognise their pits and probe or scratch them from the sand. If alarmed by such activity, the wormlion larva retracts abruptly into an S-shape under the sand, and if dug out, it retains that shape, not having much option for an alternative strategy at its disposal. Actually, because its skin is coated with sand, and it is very small, it is very easy to overlook while it lies still. However, if it is sufficiently teased after being dug out, it may begin to lash about powerfully, flinging itself away with enough force to escape its tormentor. It does not, however, hook its mouthparts into its hinder end to achieve an efficient leap such as some fruit fly and carrion fly larvae do.
The 10th and 11th segment of the larva each bears a transverse row of long hooklets that it uses in anchoring itself and in shifting sand. The fifth segment has a ventral pseudopod that helps to hold prey.
[Richards, O.W. and Davies, R. G., Imms' General Textbook of Entomology, pub: Chapman & Hall, 10th ed 1977] Not having sickle jaws like an antlion, the larva grasps prey by lashing forward and catching the victim by bending the head down to catch it between its two fang-like jaws and its pseudopod.
Like antlion larvae, vermileonid larvae are primarily found in sandy habitats, often semi-deserts, usually in the shelter of rocks or bushes, and they are voracious predators.
Classification
The infraorder Vermileonomorpha is often included within the
Tabanomorpha
The Brachyceran infraorder Tabanomorpha is a small group that consists primarily of two large families, the Tabanidae (horse and deer flies) and Rhagionidae (snipe flies), and an assortment of very small affiliated families, most of which have be ...
, though the most recent classifications place them as its
sister taxon
In phylogenetics, a sister group or sister taxon, also called an adelphotaxon, comprises the closest relative(s) of another given unit in an evolutionary tree.
Definition
The expression is most easily illustrated by a cladogram:
Taxon A and t ...
.
Species lists
Palaearctic(Broken link)
References
*Nagatomi, A. 1997. Family Vermileonidae. I: Papp, L. og Darvas, B. (red.): ''Contributions to a Manual of Palaearctic Diptera''. 2: 447-458. Science Herald, Budapest.
External links
Picture from Diptera.infoFeeding the Wormlion- By Charley Eiseman on YouTube
{{Taxonbar, from=Q1411549
Brachycera families
Vermileonomorpha