Somatochlora williamsoni
| Somatochlora williamsoni | ||||||||||||
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| Somatochlora williamsoni | ||||||||||||
| Walker , 1907 |
Somatochlora williamsoni is an emerald dragonfly species from the family of the falcon dragonflies (Corduliidae), which belong to the large dragonflies (Anisoptera). It is native to North America and is called "Williamson's Emerald" there. The species epithet honors the entomologist Edward Bruce Williamson (1877-1933), a dragonfly expert from the University of Michigan Museum of Zoology.
features
Construction of the Imago
The imago of Somatochlora William soni measures 53-59 mm, of which 40 to 48 millimeters on the abdomen ( abdominal ) omitted, which is relatively large within the genus. The abdomen is hairy on the first segment and hairless from the middle of the second segment. In addition, there is a lighter pattern of the abdomen, which is composed as follows: There are three light yellow spots on the second segment. The spots partially merge. The triangles typical of the genus are located on the third segment. The rest of the abdomen is black. The genital lobes of the males are black.
The part of the chest ( thorax ) where the wings are attached, the so-called pterothorax, is bright green and shimmers blue to purple. The color is partly covered by a fluff of yellow-brown hairs. The side stripes are only weakly pronounced and are partially barely visible. While the base of the femora is brownish, the rest of the legs are black. The hind wings measure 35 to 40 millimeters. The wings are transparent and are sometimes slightly yellowish at the base.
In the yellowish face the top of the forehead (are frons ) and the apex ( vertex ) metallic blue. The back of the head ( occiput ) is brown and the labrum greenish black.
Construction of the larva
The dark to light brown larva measures between 23 and 25 millimeters and is eight to nine millimeters wide at the widest point, the sixth segment. Dorsal hooks are found on segments five and six with nine and lateral spikes are found on the eighth and ninth segments. The rear edges of the segments are trimmed with hairs; otherwise the abdomen is hairless. The hind wing sheath extends to the middle of the sixth segment.
The femora of the rear pair of legs measure 7 to 7.3 millimeters, the rear tibiae measure 7.6 to 8.5 millimeters.
The six and a half millimeter wide head is only about three and a quarter millimeters long. While the rear edge of the head is almost straight, the corners of the occiput and the sides of the head are rounded. The joint of the lower lip ( labium ) extends to the coxae of the middle pair of legs. There are eleven or twelve hairs on the Mentum , which is roughly as long as it is wide .
Way of life
In the first few weeks after hatching, the adults fly along forests at a height of about 10 to 15 meters. Later they find their way to the breeding waters. These are slow-flowing, shady rivers. The flight altitude varies greatly with the light available. While they fly just above the water in the shade, they prefer heights of one meter above the water in the sun. Often they also stop in the air.
Spread and time of flight
The species lives in the northeastern United States and southeastern Canada . Their distribution area extends to the Appalachians . Their habitats are shady spots along slow rivers and lakes, sometimes also on bog lakes. It flies between June and September.
Similar species
The females resemble those of Somatochlora tenebrosa . In the youth stage they resemble Somatochlora elongata , but with time the light stripes on the side of the thorax fade in Somatochlora williamsoni , while they are clearly visible in S. elongata .
Individual evidence
- ↑ a b c d James George Needham , Minter Jackson Westfall , Michael L. May : Dragonflies of North America ISBN 0-945417-94-2
- ↑ Edmund Murton Walker : A New Somatochlora: With a Note on the Species Known from Ontario. In: The Canadian Entomologist . tape 39 , no. 3 , March 1907, p. 69-74 , doi : 10.4039 / Ent3969-3 .
- ^ A b Edmund Murton Walker : The North American dragonflies of the genus Somatochlora in University of Toronto studies 26