Strepsiptera

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Strepsiptera
Temporal range: 99–0 
Ma
Middle Cretaceous
- recent
Male
Stylopid female
Scientific classification Edit this classification
Domain: Eukaryota
Kingdom: Animalia
Phylum: Arthropoda
Class: Insecta
(unranked): Holometabola
Clade: Aparaglossata
Clade:
Neuropteroidea
Clade: Coleopterida
Order: Strepsiptera
Kirby, 1813
Families

The Strepsiptera (

larvae do emerge because they must find an unoccupied living host, and the short-lived males must emerge to seek a receptive female in her host.[1] They are believed to be most closely related to beetles, from which they diverged 300–350 million years ago, but do not appear in the fossil record until the mid-Cretaceous around 100 million years ago.[2]

The order is not well known to non-specialists, and the nearest they have to a common name is stylops, in reference to the genus Stylops.[3] The name of the order translates to "twisted wing", giving rise to other common names used for the order, twisted-wing insects and twisted-winged parasites.[4]

Adult males are rarely observed, although specimens may be lured using cages containing virgin females. Nocturnal specimens can also be collected at light traps.[1]

Biology

Appearance and structure

Males

Males of the Strepsiptera have wings, legs, eyes, and antennae, though their mouthparts cannot be used for feeding. Many have mouthparts modified into sensory structures. To the uninitiated the males superficially look like flies.[1] The forewings are modified into small club-shaped structures called halteres, which sense gyroscopic information.[5] A similar organ exists in flies, though in that group the hindwings are modified instead, and the two groups are thought to have independently evolved the structures.[6] The hindwings are generally fan-shaped, and have strongly reduced venation. The antennae are flabellate, and are covered in specialised chemoreceptors, likely to detect females over long distances.[7]

Adult male Strepsiptera have eyes unlike those of any other

ommatidia, that each produce a pixel of the entire image, the strepsipteran eyes consist of only a few dozen "eyelets" that each produce a complete image. These eyelets are separated by cuticle and/or setae, giving the cluster eye as a whole a blackberry-like appearance.[1][8]

Females

The females of Stylopidia, which includes 97% of all described strepsipteran species and all modern strepsipteran families except

Bahiaxenidae, are not known to leave their hosts and are neotenic in form, lacking wings, legs, and eyes, but have a well sclerotised cephalothorax (fused head and thorax).[1][9][7] Adult female mengenillids are wingless but are free living and somewhat mobile with legs and small eyes. This is probably also true for the bahiaxenids, though this has not been observed.[10][9][7]

Larvae

Newly hatched primary (first instar) larvae are on average 230 micrometres (0.0091 in) in length, smaller than many single-celled organisms. They are highly mobile with well developed stemmata, which are able to distinguish color. The underside of the body is covered in minute hair-like structures (microtrichia), which allow the larvae to stick to wet surfaces via capillary action. At the back of the body are well developed large bristle-like cerci, which are attached to muscles, which allow the larvae to jump. The tarsal segment of their legs have structures which allow them to cling to their hosts. Later larval instars which develop inside the host are completely immobile.[7]

Life cycle

polyandrous, where the female mates with more than one male.[11]

In the Stylopidia, the female's anterior region protrudes out between the segments of the hosts abdomen. In all strepsipterans the male mates by rupturing the female's

bed bugs.[1][11]

Strepsiptera eggs hatch inside the female, and the

haemocoel; this behavior is unique to these insects.[12] The offspring consume their mother from the inside in a process known as haemocoelous viviparity. Each female produces many thousands of planidium larvae.[13] The larvae emerge from the brood opening/canal on the female's head, which protrudes outside the host body.[12][13]

Larvae have legs and actively seek out new hosts. Their legs are partly vestigial in that they lack a

stemmata (simple, single-lens eyes). When the larvae latch onto a host, they enter it by secreting enzymes that soften the cuticle, usually in the abdominal region of the host. Some species have been reported to enter the eggs of hosts.[citation needed] Larvae of Stichotrema dallatorreanurn Hofeneder from Papua New Guinea were found to enter their orthopteran host's tarsus (foot).[14]

Once inside the host, they undergo

pupation to become adults. Adult males emerge from the host bodies, while females stay inside. Females may occupy up to 90% of the abdominal volume of their hosts.[1] Adult males are very short-lived, usually surviving less than five hours, and do not feed.[1]

Parasitism

Strepsiptera of various species have been documented to attack hosts in many orders, including members of the orders

winged insects, with a large number of stylopidians targeting wasps and bees, while the largest family of strepsipterans, the Stylopidae, with over 27% of all described strepsipterans, targets bees exclusively.[7]

Very rarely, multiple females may live within a single stylopized host; multiple males within a single host are somewhat more common.[1]

Strepsiptera of the family Myrmecolacidae can influence their host's behaviour, causing their ant hosts to linger on the tips of grass leaves, increasing the chance of being found by strepsipteran males (in the case of females) and putting them in a good position for male emergence (in the case of males).[19]

Taxonomy

Mengenilla moldrzyki (Mengenilidae)

The order, named by

hindwings, which are held at a twisted angle when at rest (from Greek στρέϕειν (strephein), to twist; and πτερόν (pteron), wing).[21] The forewings are reduced to halteres
.

A wasp (Odynerus spinipes) with a small portion of a strepsipteran's body protruding from its abdomen

Strepsiptera were once believed to be the sister group to the beetle families

Bahiaxenidae.[28] The earliest known strepsipteran fossils are those of Cretostylops engeli (Cretostylopdiae) and Kinzelbachilla ellenbergeri, Phthanoxenos nervosus and Heterobathmilla kakopoios (Phthanoxenidae), discovered in middle Cretaceous Burmese amber from Myanmar, around 99 million years old, which all lie outside the crown group, but are all more closely related to modern strepsiperans than Protoxenos is. The finding of a parasitic first instar in the same deposit indicates that the parasitic lifestyle of the group has likely existed nearly unchanged for 100 million years, though their evolutionary history prior to this remains a mystery.[2] The idea that mengellinids' targeting of zygentomans represents the ancestral ecology of the group as a whole has been considered questionable.[18]

Stylops melittae
male
Stem-group strepsipteran Heterobathmilla kakopoios (†Phthanoxenidae) in Burmese amber, around 100 million years old

Families

Andrena vaga male bee, with Stylops melittae mating on its abdomen

The vast majority of living strepispterans are placed within the grouping Stylopidia, which includes the families

Bahiaxenidae, are placed outside of this group, along with several extinct families.[2]

The Stylopidae have four-segmented tarsi and four- to six-segmented antennae, with the third segment having a lateral process. The family Stylopidae may be

paraphyletic.[1] The Elenchidae have two-segmented tarsi and four-segmented antennae, with the third segment having a lateral process. The Halictophagidae have three-segmented tarsi and seven-segmented antennae, with lateral processes from the third and fourth segments.[13]
The Stylopidae mostly parasitize wasps and bees, the Elenchidae are known to parasitize Fulgoroidea, while the Halictophagidae are found on leafhoppers, treehoppers, and mole cricket hosts.[13]

Strepsipteran insects in the genus Xenos parasitize Polistes carnifex, a species of social wasps.[29] These obligate parasites infect the developing wasp larvae in the nest and are present within the abdomens of female wasps when they hatch out. Here they remain until they thrust through the cuticle and pupate (males) or release infective first-instar larvae onto flowers (females). These larvae are transported back to their nests by foraging wasps.[30]

Cladogram

After:[2]

Strepsiptera

Relationship with humans

Some insects which have been considered

Inoculation of a pest population with the corresponding parasitoid may sometimes aid in reducing the impact of such pests, although no strepsipterans have ever been tested for use in this capacity, let alone being available for such purposes, either commercially or experimentally.[31]

See also

  • Entomophagous parasite

References

  1. ^ a b c d e f g h i j k l m n Whiting, M. F (2003). "Strepsiptera". In Resh, V. H.; R. T. Cardé (eds.). Encyclopedia of Insects. Academic Press. pp. 1094–1096.
  2. ^
    PMID 34478185
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  3. ^ Merriam-Webster: stylops broadly: an insect of the order Strepsiptera |[1]
  4. ^ Pierce, W. Dwight (1909). A monographic revision of the twisted winged insects comprising the order Strepsiptera Kirby. Washington: US Government.
  5. S2CID 43790345
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  6. PMID 11050348
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  7. ^
    PMID 18356032
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  8. S2CID 21888897
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  9. ^
    PMID 32719048
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  10. S2CID 84185553
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  11. ^
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  12. ^
    Greenwood Press
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  13. ^ a b c d e Borror, D.J.; Triplehorn, C.A.; Johnson, N.F. (1989). Introduction to the Study of Insects (6 ed.). Brooks Cole.
  14. PMID 11703867
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  15. PMID 12788973
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  16. ^ Beani, Laura (2006). "Crazy wasps: when parasites manipulate the Polistes phenotype" (PDF). Annales Zoologici Fennici. 43: 564–574.
  17. S2CID 83484969
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  18. ^
    doi:10.1016/j.cretres.2015.10.008
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  19. JSTOR 3494966
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  20. ^ Pierce, William Dwight (1909). A monographic revision of the twisted winged insects comprising the order Strepsiptera Kirby. Government Printing Office. pp. 209.
  21. ^ Kathirithamby, Jeyaraney (2002). "Strepsiptera". The Tree of Life Web Project. Archived from the original on July 15, 2017.
  22. PMID 12064233
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  23. ^
    PMID 11975347
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  24. S2CID 25178911
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  25. PMID 12066692
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  26. S2CID 92390950
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  27. S2CID 85232914
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  28. S2CID 83936131
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  29. doi:10.11646/zootaxa.1104.1.3
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  30. S2CID 9691419
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  31. ISBN 978-9400722194
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Further reading

External links

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