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Strepsiptera

Stylops; Twisted-winged parasites

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Kinds

Overview
Commonly called twistedwing parasistes, these insects are mostly internal parasites of other insects. Males differ greatly from females in structure. Males have wide heads with compound eyes on the sides. Males also have fan shaped antennae. Their forewings have evolved into clublike structures and the hind wings are membranous and with out venation. Females are without legs, wings, antennae and often eye and remain in the host their entire lives. The females remain in the host with only their heads protruding. Males leave the host and find females to mate with. The newly hatched, well-developed larvae leave the female and fall from the host to the ground or to plants.

Twistedwing parasites enter their insect hosts as larva through joints or sutures when the host itself is still in its larval stage. From there they undergo what is called "hypermetamorphosis": They molt into another, less mobile, larval form and feed in the host's body cavity. From there they undergo holometabolous metamorphosis. Hosts are not usually killed by infection but may be injured. The shape and color of the abdomen may be changed and the sex organs of the host may be damaged. The male usually causes more damage to the host than the female. Common hosts are various species from the orders Orthoptera, Hemiptera, Hymenoptera and Thysanura.


Identification
  • Immatures:
    1. First instar (triungulin) has legs, high mobility
    2. Successive instars are legless and grub-like with reduced mouthparts
  • Adults:
    1. Females remain larviform, legless and wingless, partially projecting from host's abdomen.
    2. Males emerge with adult-like body; Large fan-shaped hind wings; small club-like front wings; Reduced mandibulate mouthparts; Antennae 4- to 7-segmented; often with lateral branching"-- (N.C. State University Entomology Dept.)

Phylogeny
Taxonomic Category Scientific Name Common Name
Phylum Arthropoda Arthropods
Class Insecta Insects
Order Strepsiptera Twisted-winged parasites

Photographs
[Species: Xenos ssp.]
Photo copyright Birgit Ehmer 		[Species: Xenos. ssp.]
Photo copyright Birgit Ehmer 		[Species: Elenchus tenuicornis ]
Photo copyright Hans Pohl

[Species: Mengea tertiaria ]
Photo copyright Hans Pohl		 [Species: Xenos vesparum ]
Photo copyright Hans Pohl		 [Family: Stylopidae ]
Photo copyright Dept. of Entomology: Penn State
[Order: Strepsiptera ]
Photo copyright E. R. Day		 [Order: Strepsiptera ]
Photo copyright Hans Pohl		 [Order: Strepsiptera ]
Photo copyright Rick Redak
[Species: Mengenilla chobauti]
Photo copyright Hans Pohl		 [Species: Eoxenos laboulbenei]
Photo copyright Hans Pohl		 [Species: Stichotrema dallatorreanum]
Photo copyright Hans Pohl
[Species:Stichotrema dallatorreanum]
Photo copyright Hans Pohl

Geographic distribution
North America
 Worldwide
Number of Families 4 8
Number of Species 109 532

Natural history
Most Strepsiptera (also known as twisted-wing parasites) live as internal parasites of bees, wasps, grasshoppers, leafhoppers, and other members of the order Hemiptera. Only a few species that parasitize bristletails (Archeognatha) are known to be free-living in the adult stage.

Strepsiptera share so many characteristics with beetles that some entomologists classify them as a superfamily of Coleoptera. In fact, Strepsiptera and certain parasitic beetles (in the families Meloidae and Rhipiphoridae) are among the very few insects that undergo hypermetamorphosis, an unusual type of holometabolous development in which the larvae change body form as they mature. Upon emerging from their mother's body, the young larvae, called triunguloids, have six legs and crawl around in search of a suitable host. In species that parasitize bees or wasps, a triunguloid usually climbs to the top of a flower and waits for a pollinator. When a host arrives, the larva jumps aboard, burrows into its body, and quickly molts into a second stage that has no distinct head, legs, antennae or other insect-like features. These larvae grow and continue to molt inside the host's body cavity, assimilating nutrients from the blood and non-vital tissues. After pupating in the host, winged males emerge and fly in search of mates. An adult female remains inside her host, managing to attract and mate with a male while only a small portion of her body protrudes from the host's abdomen. Embryos develop within the female's body, and a new generation of triunguloid larvae begin their life cycle by escaping through a brood passage on the underside of her body.

Adult male Strepsiptera are strange-looking insects. The head is small, with protruding compound eyes that look like tiny raspberries. The antennae are multi-segmented and have up to three branches. Front wings are reduced to small, club-like structures; hind wings are very large and fan-shaped."-- (N.C. State University Entomology Dept.)


Links to other sites

Acknowledgements
Aeneas Munane, Biology Major, University of Georgia, Athens.

Thanks to Sabina Gupta, Denise Lim, and Dr. John Pickering for technical and web support in developing this page.



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Order - STREPSIPTERA
(Greek, strepsis = twisting; pteron = wing)
Common Name: stylops
Distribution: Cosmopolitan

Description
Twisted-winged parasites or Strepsiptera usually have active first stage larvae that attach to adult hosts (usually bees or wasps in North American species), ride back to the host’s nest and burrow into the host’s larva where they develop as legless internal parasites, staying inside their hosts at least until adulthood. The strange twisted-winged adults which give rise to the common name of the family are all males, as females are wingless and legless and never leave the host (there are a few non-parasitic species in which the females have legs). Male strepsipterans have big eyes, antler-like antennae, large, twisted hind wings, and tiny front wings which look and function like the halters of flies. Twisted-winged parasites are widespread, but you are not too likely to see any winged males unless you rear them from their distinctively distorted parasitised hosts, as they live just long enough to find a host parasitised by a female. This photo shows a paper wasp with strepsipteran pupae sticking out between the abdominal tergites.

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Following modified from Lucid via Discover Life
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An adult male strepsipteran

Order - STREPSIPTERA
(Greek, strepsis = twisting; pteron = wing)
Common Name: stylops
Distribution: Cosmopolitan

Description
Members of the order Strepsiptera are highly specialised parasites of other insects. For some time they were considered to be modified beetles, however this is no longer believed. However, the strepsipterans are probably closely related to Coleoptera (beetles) or Diptera (flies). The species within this order show an extreme form of sexual dimorphism: the adult male is a free-living winged insect, while the adult female is a "maggot-like" organism within the body of the host (endoparasite). Adult males have bulging compound eyes with a few facets - there are no simple eyes (ocelli). Mandibles are present but small. The forewings are reduced to stubs but the hind wings are broad with a few veins. Males live for only a few hours after leaving their hosts and probably do not feed - their only activity is to find females for reproduction. Males are quite small (less than 5 mm long) and are probably not rare but their small size and short life spans means that they are not often encountered. Females remain within the body of the host insect.

Larva
Eggs hatch within the female strepsipteran and the juveniles travel out of the female's brood passage to the surface of the host. Juveniles leave while the host is visiting a flower. The larvae are 6-legged and have compound eyes but lack antennae and mandibles. They attach themselves to an insect visiting the flower on which they have alighted. The parasite absorbs nutrients directly through its skin. Females never develop any further than an advanced "maggot" form and protrude their forepart through the host cuticle when involved in fertilisation. Males pupate in the host and then emerge by pushing off a small cuticle cap which protrudes from the host's body. Females attract males by scent (pheromones).

Members
Stylops - most representatives are not commonly known.

Food
Strepsipterans feed on the body of other insects. Hosts include bees, wasps or other members of the Order Hymenoptera .

 Importance
The importance of strepsipterans is unknown at present.

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Updated: 2009-11-21 01:12:48 gmt
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