Aeshna crenata
Aeshna crenata Hagen, 1856
Local names: Siberian hawker, Sibirische Mosaikjungfer, Siberische glazenmaker, Æschne crénelée, Sibirisk mosaikslända
Species Information
Description
An impressive hawker, the largest species of the genus Aeshna. Most like Aeshna Serrata but more likely to be confused with A. juncea or A. subarctica which can be found in the same habitats.
Males are intensely blue, with only blue or black markings on the abdomen. Blue to emerald eyes, with all black back-sides (like A. juncea and A. subarctica). The leading edge of the wings, the Costa, is brown like A. subarctica. A. juncea and A. serrata both have yellow leading edges. Black markings on the frons T-shaped with a thick stem. Lateral markings on thorax are mainly yellow, wide and clearly visible in flight, in both sexes, and can be used to distinguish from A. juncea and A. subarctica in flight. Also, in flight, the last segmenst tend to dip, giving the abdomen in a bow-like profile.
Females most often brown and pale grey-blue, but some are blue like the males. Older females have dark bands on the wings, between the pterostigma and the node, visible also in flight. This is a diagnostic feature, all other similar species have evenly coloured wings, even those with darker wings. Female appendages are pointed, not rounded.
Size
Habitat
In both Finland and the Baltic states, Aeshna crenata seems to have rather specialized habitat requirements and occurs mainly in small, circular, oligotrophic forest ponds with a swampy shoreline, sustained by clear groundwater. In most cases the banks are covered with a vegetation of peat moss, beakrush and sedges, followed by mature forests in the direct vincinity. In the northern and eastern parts of European Russia the habitat spectrum is wider, also including non-acidic water, larger lakes and river backwaters with oxbow ponds and lakes and a vegetation of water horsetail and sedges. In Siberia the species is eutryphic.
Distribution
Found from north-east Europe to Kamchatka, Sachalin, South Korea and Japan. In Europe it is found in scattered populations in southern Finland, eastern Lithuania, south-eastern Latvia, northern Belarus and Russia. It is probably not uncommon in northern Russia but as far is known absent from the southern parts of Russia, except the southern Urals, where it is common.
Flight Period
End of June to mid-September, peaking in second half of July and August.
Behavior
Often flies with a partly gliding flight, most visible in patrolling males. Male can be very aggressive and hunt other hawker males from their territory. They often patrol around 1.5 - 2 m above the water surface, slightly higher than the other co-existing species. It often perches directly on tree stems near their preferred waters.
Relatively stationary and is rarely seen outside known habitats.
Eggs are oviposited in water edges in floating sphagnum, seges or other organic material in or just below the water surface. The larva is the largest of the hawkers, its development probably three years long or more. Exuvia is found in knee-deep or slightly deeper waters on straws of e .g. sedges.
Similar Species
Aeshna juncea, Aeshna subarctica, Aeshna serrata
External Links
Genus: Aeshna
Aeshna, or the hawkers or mosaic darners, is a genus of dragonflies from the family Aeshnidae. Species within this genus are generally known as hawkers in Europe or darners in America.
Identification
Aeshna spp. are best identified by excluding other aeshnid genera. The species generally have dark bodies with coloured bands on the thorax and their abdomen is basically dark with a mosaic of paired coloured spots. Males have auricles and an anal triangle of 2-4 cells (except I. isoceles).
Separation from other genera
Brachytron are the closest relative, from which the Aeshnas differ by numerous, although somewhat relative, features. These includes Brachytron having an early flight season, smaller size, hairier body, thinner pterostigma and abdomen not waisted. In the hand it is easier to study diagnostic details of venation and markings. Anax differs in shape and wing venation, but is ruled out in the field by the plain thorax and pale abdomen. They also have a black band on the upperside (except the conspicuous A. immaculifrons). Boyeria and Caliaeschna differ in wing venation.
Separation of the species
A large and diverse group. The majority of the world's species occurs in North America. Each species, except for a few pairs of similar species, has several unique features.
Behaviour
Often seen hawking (hence the common name) in open but sheltered places. I can be glades or gardens, as well as over open waters. Foraging individuals often concentrate at good sites, especially towards the end of the day. Males patrol swiftly over water, often aggressively territorial. They usually follow a fairly fixed and often extensive route, frequently interrupting direct flight with hovering pauses and dashes toward other individuals. A, affinis is the only species that oviposit in tandem with the male, all other Aeshna females oviposit alone.
Family: Aeshnidae
The Aeshnidae, also called aeshnids, hawkers, or darners, is a family of dragonflies. The family includes the largest dragonflies found in Europe and North America and among the largest dragonflies on the planet.
Description
Common worldwide or nearly worldwide. Genera are Aeshna and Anax. The African Anax tristis has a wingspan over 125 mm, making it one of the world's largest known dragonflies. Most European species belong to Aeshna. Their American name darner stems from the female abdomens looking like a sewing needle, as they cut into plant stem when they lay their eggs.
The dragonflies mate in flight. The eggs are deposited in water or close by. The larvae (nymphs or naiads) are generally slender compared to those of other families, with a long and flat extensible lower lip (labium). The larvae are aquatic predators, feeding on other insects and even small fish.
The adults spend large amounts of time in the air and seem to fly tirelessly. They can fly forwards or backwards or hover like a helicopter. The wings are always extended horizontally.
The abdomen are mostly colored blue and or green, with black and occasionally yellow. The large, hemispherical, compound eyes touch in the midline. Individuals of this family have an extremely good sight, and are voracious insect predators.
A proposal has been made to split this family into Aeshnidae and Telephlebiidae.
The name may have resulted from a printer's error in spelling the Greek Aechma, a spear. The spelling Aeschnidae has been intermittently used over a period of time, but is now abandoned for the original name Aeshnidae. However, derived genus names (such as Rhionaeschna) retain the 'sch' spelling, as this is how they were first cited.