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Some Basic Info.
The order Odonata is split into two suborders: Epiprocta and Zygoptera, the dragonflies and the damselflies. Epiprocta used to be split into two suborders the anisoptera and anisozygoptera, however recently it was discovered that these two suborders shared a paraphyletic collection of lineages and so anisozygoptera are now considered an infraorder of anisoptera (Rehn, A.C. 2003). Anisoptera are considered the perfect hunting machines, with the capability to see in any direction, two pairs of independent and exceptionally strong wings unusual for insects to have (Silsby, 2001). But these wings allow for flight in any direction and hovering for extended periods of time and the thorax abdomen morphology is structured for capturing and feeding on prey while flying (Trueman & Rowe, 2009). Morphology The Body: The head is large, however the it is dominated by a pair of of compound eyes that touch. Each eye contains 30,000 ommatidia (facets) and each ommatidium contains several types of receptors. The receptors are specific to the location of the ommatidium (dragonflies have four to 5 opsin per facet). For example upward facing facets have blue and/or ultraviolet light receptors whereas down facing facets have longer wavelength receptors. Although it is not known for sure what they see it is hypothesized that the sky is considerably brighter and so it is much clearer to see objects against the sky (Kleef, 2008) (GrrlScientist, 2009). The face of dragonflies also carries three ocelli near the base of the pair of short antennae (Trueman & Rowe, 2009). These ocelli are hypothesised to not just detect light intensity but also the direction of a movement, whether it's based from the animal itself or from an object passed the animal is unclear (Kleef, 2008) (Gonzalez-Bellido et al. 2012). With all this information the ocelli function in stabilising flight reflex actions (GrrlScientist, 2009) (Trueman & Rowe, 2009). The thorax is also quite large and strong as it contains the flight muscles used to power the wings. The legs are angled in such a way that they're more suited for holding captured prey rather than walking (Silsby, 2001). The abdomen is long, flexible with 10 segments that terminates to clasping organs in both sexes. Females of several anisopterans families carry a distinct ovipositor under abdominal segments 9-10. Whereas the males possess secondary genitalia on the underside of abdominal segments 2-3 (Silsby, 2001). The Wings At rest: The wing veins are fused at the base and the wings cannot be folded over the body at rest like a similar insect the damselfly does (Silsby 2001)(Trueman & Rowe, 2009). All but one anisopteran genus settle their wings out sideways or slightly downward. The one anisopteran genus (Cordulephya, Corduliidae) the wings are held in the damselfly resting position where the wings rest perpendicular to the body (Silsby 2001)(Trueman & Rowe, 2009). The wings of adult anisopterans have two pairs of wings, the hind wing is slightly broader than the fore wing (Silsby 2001)(Trueman & Rowe, 2009). There are five main vein stems, with a nodus where the second main vein meets the leading edge of the wing (Silsby 2001)(Trueman & Rowe, 2009). In most families a conspicuous pterostigma is carried near the wing tip (Silsby 2001)(Trueman & Rowe, 2009). |