FAQs on Dragonflies
- How big do they get?
- The biggest reported wingspan of a living dragonfly is the Central American
Megaloprepus coerulatus, with a wingspan about 19 cm in some
individuals. This is a thin, long-abdomened damselfly (picture).
The bulkiest dragonfly may be Petalura ingentissima from Australia
(female wingspan to about 16 cm)(a rather smaller male (150 mm) here), a central African Anax species or
Tetracanthagyna plagiata, an aeshnid from Borneo (female wingspan to
about 18 cm).
The largest recognised member of the extinct Protodonata was the Permian
Meganeuropsis permiana with a reconstructed wingspan (based on
fragments, scaled to complete fossils of similar animals) of about 70-75 cm.
- How small do they get?
- Small larvae are about 1 mm long at hatching (which isn't what you wanted
but remember the animal is the whole life history). The smallest adult
Zygoptera (damselflies) are in the genus Agriocnemis with wingspans of
17-18 mm. The smallest adult Anisoptera (dragonflies proper) are probably
Nannophyopsis chalcosoma from Borneo, which is even smaller than
Nannophya pygmaea (which has a wingspan about 25mm).
- How fast do they fly?
- Claims of 60 mph were poorly based. Current workers are comfortable with
estimates between 30 and 60 kph. Because of the erratic flight movements it is
very hard to measure peak speeds of flying dragonflies.
- How do they fly?
- At least four physically distinct flight mechanisms seem to be used by
dragonflies. Most flight involves short wing strokes, well above the point of
criticality, but the wingstroke is too short for the boundary layer to
separate. Unsteady-state airflows are also implicated. Dragonflies can fly
forwards at > 100 body-lengths/s, backwards at > 3 body-lengths/s and
hover; all while maintaining their body horizontal!
- How old do they get?
- In most temperate species individuals live less than a month as adults.
However, in some species individuals regularly survive for up to 6 months. No
dragonfly is known which lives a year as an adult. Larval life spans can
approach a decade in alpine and high arctic habitats. There are no precise data
on such long-lived larval forms.
- What is the shortest life-history?
- Egg to adult durations of about 40 days are recorded from small tropical
damselflies and from relatively large dragonflies which occupy temporary pools.
There is a further period of some days before the adult reaches sexual
maturity.
- How well do they see?
- Resolving powers below 15' of arc are documented from the field.
- What's the difference between a dragonfly and a damselfly?
- Damselfly is a name given to members of the suborder Zygoptera. These
animals are generally of slim build, their eyes are always widely
separated, their fore- and hindwings are similar in shape and are narrowed at
the base. Most species rest with their wings held above the abdomen. The
larvae are slender with cylindrical abdomens and have three (rarely two)
leaf-like gill structures at the end of the abdomen.
Dragonfly is a name which can be used for all Odonata, but is often restricted
to members of the suborder Anisoptera. These are generally larger, more robust
animals. In most species the eyes touch, or almost touch, at the top of
the head; the fore and hind wings differ in shape (the base of the hindwings
being broader) and the wingbases are quite broad. The wings are usually
held spread when at rest. The larvae are robust, the abdomen is broader than
the thorax and somewhat dorso-ventrally flattened. The rectum is enlarged and
contains specialised gill structures. There are no leaf-like caudal appendages.
- How many kinds are there?
- About 5000 species of Odonata are presently formally described. Some of
these 'species' will sink in synonymy, new species will be discovered, and
sibling species will be distinguished. Expert 'guesses' put the total number of
species at between 5500 and 6500.
Zoology
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