Mecoptera

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Mecoptera
Temporal range: Early Permian - Recent
Panorpa communis, male
Scientific classification Edit this classification
Domain: Eukaryota
Kingdom: Animalia
Phylum: Arthropoda
Class: Insecta
(unranked):
Antliophora
Order: Mecoptera
Packard, 1886
Comstock, 1895
Families

Mecoptera (from the

Boreidae
, adults of which are sometimes seen walking on snowfields. In contrast, the majority of species in the order inhabit moist environments in tropical locations.

The Mecoptera are closely related to the

leaf litter
or moss, and the eggs may not hatch until the wet season arrives. The larvae are caterpillar-like and mostly feed on vegetable matter, and the non-feeding pupae may pass through a diapause until weather conditions are favorable.

Early Mecoptera may have played an important role in pollinating extinct species of gymnosperms before the evolution of other insect pollinators such as bees. Adults of modern species are overwhelmingly predators or consumers of dead organisms. In a few areas, some species are the first insects to arrive at a cadaver, making them useful in forensic entomology.[9]

Diversity

Mecopterans vary in length from 2 to 35 mm (0.1 to 1.4 in). There are about six hundred

Bittacidae. Besides this there are about four hundred known fossil species in about eighty-seven genera, which are more diverse than the living members of the order.[10] The group is sometimes called the scorpionflies, from the turned-up "tail" of the male's genitalia in the Panorpidae.[11]

Distribution of mecopterans is worldwide; the greatest diversity at the species level is in the Afrotropic and Palearctic realms, but there is greater diversity at the generic and family level in the Neotropic, Nearctic and Australasian realms. They are absent from Madagascar and many islands and island groups; this may demonstrate that their dispersal ability is low, with Trinidad, Taiwan and Japan, where they are found, having had recent land bridges to the nearest continental land masses.[10]

Evolution and phylogeny

Taxonomic history

The European scorpionfly was named Panorpa communis by Linnaeus in 1758.[12] The Mecoptera were named by Alpheus Hyatt and Jennie Maria Arms in 1891.[13] The name is from the Greek, mecos meaning long, and ptera meaning wings.[14] The families of Mecoptera are well accepted by taxonomists but their relationships have been debated. In 1987, R. Willman treated the Mecoptera as a

Siphonaptera (fleas).[16]

Fossil history

Among the earliest members of the Mecoptera are the

Upper Permian age. Fossil Mecoptera become abundant and diverse during the Cretaceous, for example in China,[17] where panorpids such as Jurassipanorpa, hangingflies (Bittacidae and Cimbrophlebiidae), Orthophlebiidae, and Cimbrophlebiidae have been found.[18][19]

Extinct Mecoptera species may have been important pollinators of early

Gnetales, which have ovulate organs that are either poorly suited for wind pollination or have structures that could support long-proboscid fluid feeding.[20][21] The Aneuretopsychina were the most diverse group of mecopterans in the Latest Permian, taking the place of the Permochoristidae, to the Middle Triassic. During the Late Triassic through the Middle Jurassic, Aneuretopsychina species were gradually replaced by species from the Parachoristidae and Orthophlebiidae. Modern mecopteran families are derived from the Orthophlebiidae.[22]

External relationships

Mecoptera have special importance in the evolution of the insects. Two of the most important insect orders,

Trichoptera (caddisflies), probably evolved from ancestors belonging to, or strictly related to, the Mecoptera. Evidence includes anatomical and biochemical similarities as well as transitional fossils, such as Permotanyderus and Choristotanyderus, which lie between the Mecoptera and Diptera. The group was once much more widespread and diverse than it is now, with four suborders during the Mesozoic.[23]

It is unclear as of 2020 whether the Mecoptera form a single clade, or whether the

Boreidae[24][16][25] is not supported; instead, there is the possibility that they are sister to another Mecopteran family, the Nannochoristidae. The two possible trees are shown below:[26]

(a) Mecoptera (clades in boldface) is paraphyletic, containing Siphonaptera:[26][27]

part of Holometabola
Antliophora

Diptera (true flies)

Pistillifera (scorpionflies, hangingflies, 400 spp.)

Boreidae (snow scorpionflies, 30 spp.)

Nannochoristidae (southern scorpionflies, 8 spp.) 

Siphonaptera (fleas, 2500 spp.)

Mecoptera

Trichoptera (caddisflies)

Lepidoptera (butterflies and moths)

Hymenoptera (sawflies, wasps, ants, bees)

(b) Mecoptera is monophyletic, sister to Siphonaptera:[26]

part of Holometabola
Antliophora

Diptera (true flies)

Mecoptera

Pistillifera (scorpionflies, hangingflies, 400 spp.)

Boreidae (snow scorpionflies, 30 spp.)

Nannochoristidae (southern scorpionflies, 8 spp.)

Siphonaptera

(fleas, 2500 spp.)

Trichoptera (caddisflies)

Lepidoptera (butterflies and moths)

Hymenoptera (sawflies, wasps, ants, bees)

Internal relationships

All the families were formerly treated as part of a single order, Mecoptera. The relationships between the families are, however, a matter of debate. The cladogram, from Cracraft and Donoghue 2004, places the Nannochoristidae as a separate order, with the Boreidae, as the sister group to the Siphonaptera, also as its own order. The

Bittacidae unclear. Of those other families, the Meropeidae is the most basal, and the relationships of the rest are not completely clear.[28]

Nannomecoptera
Neomecoptera

Boreidae (snow scorpionflies)

Siphonaptera (fleas)

Mecoptera

Eomeropidae (mainly fossil (Triassic to present), 1 extant sp.)

(?)

Bittacidae[b]
(hangingflies)

Meropeidae (earwigflies)

Choristidae (Australian scorpionflies)

Apteropanorpidae (Tasmanian snow scorpionflies)

(?)

Bittacidae[b] (hangingflies)

Panorpodidae (short-faced scorpionflies)

Panorpidae (Jurassic to present, common scorpionflies)

sensu stricto
  1. ^ Some studies find Nannomecoptera as sister to the Boreidae+Siphonaptera clade.[16]
  2. ^
    Bittacidae
    is unclear. Two alternative positions, either basal within Mecoptera sensu stricto or sister to Panorpodidae, are shown.
Male Panorpa dubia.
A, Body in lateral view; B–D. male genital bulb and gonostyli. B, dorsal view; C, ventral view; D, lateral view. ep, epandrium; gcx, gonocoxite; gs, gonostylus; hv, hypovalva; hyp, hypandrium. Scale bars represent 3 mm in A, 1 mm in B–D

Biology

Morphology

Mecoptera are small to medium-sized insects with long beaklike

ocelli on the top. The antennae are filiform (thread-shaped) and contain multiple segments.[23][29]

The fore and hind wings are similar in shape, being long and narrow, with numerous cross-veins, and somewhat resembling those of primitive insects such as mayflies. A few genera, however, have reduced wings, or have lost them altogether. The abdomen is cylindrical with eleven segments, the first of which is fused to the metathorax. The cerci consist of one or two segments. The abdomen typically curves upwards in the male, superficially resembling the tail of a scorpion, the tip containing an enlarged structure called the genital bulb.[23][29]

The caterpillar-like larvae have hard sclerotised heads with mandibles (jaws), short true legs on the thorax, prolegs on the first eight abdominal segments, and a suction disc or pair of hooks on the terminal tenth segment. The pupae have free appendages rather than being secured within a cocoon (they are exarate).[29]

Ecology

A Panorpid scorpionfly feeding on a dead insect

Mecopterans mostly inhabit moist environments although a few species are found in semi-desert habitats. Scorpionflies, family Panorpidae, generally live in broad-leaf woodlands with plentiful damp leaf litter. Snow scorpionflies, family Boreidae, appear in winter and are to be seen on snowfields and on moss; the larvae being able to jump like fleas. Hangingflies, family Bittacidae, occur in forests, grassland and caves with high moisture levels. They mostly breed among mosses, in leaf litter and other moist places, but their reproductive habits have been little studied, and at least one species, Nannochorista philpotti, has aquatic larvae.[10]

Adult mecopterans are mostly scavengers, feeding on decaying vegetation and the soft bodies of dead invertebrates. Panorpa raid spider webs to feed on trapped insects and even the spiders themselves, and hangingflies capture flies and moths with their specially modified legs. Some groups consume pollen, nectar, midge larvae, carrion and moss fragments.[10] Most mecopterans live in moist environments; in hotter climates, the adults may therefore be active and visible only for short periods of the year.[23]

Mating behaviour

Panorpa communis mating

Various courtship behaviours have been observed among mecopterans, with males often emitting pheromones to attract mates. The male may provide an edible gift such as a dead insect or a brown salivary secretion to the female. Some boreids have hook-like wings which the male uses to pick up and place the female on his back while copulating. Male panorpids vibrate their wings or even stridulate while approaching a female.[10]

Hangingflies
have distinct mating behaviour.

Hangingflies (Bittacidae) provide a nuptial meal in the form of a captured insect prey, such as a caterpillar, bug, or fly. The male attracts a female with a pheromone from vesicles on his abdomen; he retracts these once a female is nearby, and presents her with the prey. While she evaluates the gift, he locates her genitalia with his. If she stays to eat the prey, his genitalia attach to hers, and the female lowers herself into an upside-down hanging position, and eats the prey while mating. Larger prey result in longer mating times. In Hylobittacus apicalis, prey 3 to 14 millimetres (0.12 to 0.55 in) long give between 1 and 17 minutes of mating. Larger males of that species give prey as big as houseflies, earning up to 29 minutes of mating, maximal sperm transfer, more oviposition, and a refractory period during which the female does not mate with other males: all of these increase the number of offspring the male is likely to have.[30]

Life-cycle

The female lays the eggs in close contact with moisture, and the eggs typically absorb water and increase in size after deposition. In species that live in hot conditions, the eggs may not hatch for several months, the larvae only emerging when the dry season has finished. More typically, however, they hatch after a relatively short period of time. The larvae are usually quite caterpillar-like, with short, clawed, true legs, and a number of abdominal prolegs. They have sclerotised heads with mandibulate mouthparts. Larvae possess compound eyes, which is unique among holometabolous insects.[31] The tenth abdominal segment bears either a suction disc, or, less commonly, a pair of hooks. They generally eat vegetation or scavenge for dead insects, although some predatory larvae are known. The larva crawls into the soil or decaying wood to pupate, and does not spin a cocoon. The pupae are exarate, meaning the limbs are free of the body, and are able to move their mandibles, but are otherwise entirely nonmotile. In drier environments, they may spend several months in diapause, before emerging as adults once the conditions are more suitable.[23]

The raised scorpion-like tail of the male has earned the scorpionflies a sinister reputation, but they do not sting.

Interaction with humans

corpses. In areas where the family Panorpidae occurs, such as the eastern United States, these scorpionflies can be the first insects to arrive at a donated human cadaver, and remain on a corpse for one or two days. The presence of scorpionflies thus indicates that a body must be fresh.[32][9]

Scorpionflies are sometimes described as looking "sinister", particularly from the male's raised "tail" resembling a scorpion's sting.[33] A popular but incorrect belief is that they can sting with their tails.[34]

References

  1. PMID 23950679
    .
  2. .
  3. ^ .
  4. .
  5. .
  6. .
  7. .
  8. .
  9. ^ a b "Southeast Texas Applied Forensic Science Facility". STAFS.
  10. ^ .
  11. ^ "Scorpionflies (Order: Mecoptera)". Amateur Entomologists' Society. Retrieved 5 July 2020.
  12. Systema naturae
    per regna tria naturae, secundum classes, ordines, genera, species, cum characteribus, differentiis, synonymis, locis. Laurentii Salvii, Holmiae [= Stockholm]. Vol. Tomus I, Editio decima, reformata: i–ii, 1–824.
  13. .
  14. S2CID 3947767. {{cite book}}: |journal= ignored (help
    )
  15. .
  16. ^
    S2CID 56100681. Archived from the original
    on 2013-01-05.
  17. .
  18. .
  19. .
  20. .
  21. .
  22. PMID 22259282. {{cite book}}: |journal= ignored (help
    )
  23. ^ .
  24. .
  25. . Recently, a close affinity between Siphonaptera and Mecoptera has been convincingly demonstrated via morphology (Bilinski et al. 1998) and molecular data (Whiting 2002), rendering Mecoptera paraphyletic, but making the clade including Mecoptera and Siphonaptera monophyletic
  26. ^ .
  27. .
  28. .
  29. ^ .
  30. .
  31. .
  32. ^ Rutsch, Poncie (22 January 2015). "Finding Crime Clues In What Insects Had For Dinner". NPR. Retrieved 22 June 2015.
  33. ^ "Weirdest Looking Bugs". EnkiVillage. 2015-05-13. Retrieved 22 June 2015.
  34. ^ Newton, Blake. "Scorpionflies & Hangingflies". University of Kentucky. Retrieved 25 February 2017.

External links