Salutations, BugFans,<\/p>\n
What better way to end the old year than with a spectacular dragonfly (charismatic megafauna), and many thanks to BugFan Freda, guest photographer.<\/p>\n
The BugLady is yearning for a Shadow darner. The books say they\u2019re common, and other people are up to their ankles in them, but not the BugLady, although she scared up some big, dark darners in early fall that didn\u2019t stick around to have their pictures taken. She has read that Shadow darners may collect in small groups on tree trunks, but really, one would be enough.<\/p>\n
Darners are large dragonflies in the family Aeschnidae. They\u2019re big-eyed and powerful dragonflies that are sexually dimorphic (males and females look different), and the females of many species are called polymorphic<\/em> (many forms, because they come in several different color phases). Mosaic darners (genus Aeshna<\/em>) get their names from the blue \u201cmosaic\u201d patches on the abdomens of the males. Caveat—if you\u2019re using a camera instead of a hand lens to identify some of the mosaic darners, the ID is a \u201cprobably.\u201d<\/p>\n Shadow darners (Aeshna umbrosa<\/em>) live throughout most of North America (except the very southern edges of the U.S. and a few Rocky Mountain states), and their range stretches well north into the boreal forests of Canada. They\u2019re found in a variety of wetlands, from the still waters of bogs, pools, and ditches, to slow streams. There is an eastern subspecies (Aeshna umbrosa umbrosa<\/em>) and a western one (A. umbrosa occidentalis<\/em>), with slight differences in coloration (the former has small, green abdominal spots and the latter has blue ones). See an awesome comparison of the subspecies, at https:\/\/www.flickr.com\/photos\/gyr\/sets\/72157614135970414?view=sm<\/a>.<\/p>\n Overall, this is a large, brown dragonfly (some sources refer to it as dull) that\u2019s around 3″ long with a wingspread close to 4″. The all-important lateral thoracic stripes are straight and generally pale, and an Ohio DNR wildlife website says that \u201cthe green mark on fore part of thorax often resembles the Nike \u2018swoosh.\u2019\u201d The face is pale and lacks a conspicuous black stripe across it (males may show a hairline stripe), and the male\u2019s cerci<\/em>, described as \u201cwedge-shaped\u201d by some references and \u201cpaddle-shaped\u201d by others, are spine-tipped. Females\u2019 wings may be brown-tinted. Some sources say that the thoracic stripes are outlined in black—not an \u201cin flight\u201d field mark (but see link, above).<\/p>\n As their name suggests, Shadow darners spend most of their lives in shady woods and edges, and they may fly until it\u2019s too dark to see them (though they\u2019re more likely to be active during the daylight when the cooler weather of fall sets in). Shadow darners are associated with the tail end of the dragonfly season; almost three-quarters of Wisconsin sightings are in August and September, but there are May records and they are seen well into October.<\/p>\n [metaslider id=551]<\/p>\n What do bumblebees and Shadow darners have in common? They push the limits of cold-bloodedness, remaining active in very cool temperatures, when other dragonflies are grounded. Odonates use a variety of strategies to regulate their body temperature—passively, by basking to collect heat or assuming the obelisk position to avoid it; and actively, by contracting the wing muscles\/quivering their wings while perched (wing whirring), to warm up the flight muscles (and therefore the thorax), and also by slowing circulation to the abdomen in order to keep heat in the thorax instead of sending it to the abdomen, where the larger surface area allows cooling). Their colors may darken in cold weather, and dark colors absorb more radiation from the sun. An overheated Shadow darner may immerse its abdomen in water (water dipping).<\/p>\n Shadow darners are agile and active flyers, scooping small, soft-bodied insects (and the occasional fellow-Odonate) out of the air into legs arranged like a basket, discarding the wings, and feeding in flight. One source said that they consume as much as 20% of their bodily weight daily. They sometimes form feeding swarms or join other darners in mixed swarms. They are, in turn, fed upon by raptors, especially the smaller falcons, and by purple martins. Ovipositing females may fall prey to frogs (one well-annotated source added predation on females by salamanders\/newts, which raised the BugLady\u2019s eyebrows. She consulted her herp guy, and he couldn\u2019t picture a salamander taking on a large darner, either—a salamander lucky enough to grab a dragonfly doesn\u2019t have the equipment to process it into smaller pieces (and many salamanders are in the 3\u201d to 4\u201d size range, themselves) (thanks, BugFan Tom). Naiads, like their elders, are unapologetic carnivores, feeding underwater on any aquatic invertebrate (or small tadpole, larval salamander or fish) that they can wrap their labium around, and being fed on by a variety of parasites (therefore, warns one site, do not eat dragonflies!) and by fish and birds.<\/p>\n There\u2019s not much of a courtship, and even less of a honeymoon. Females mate with the owner of the territory they enter (or they don\u2019t, arching their body in the opposite direction to show lack of interest). He takes her to a promising spot, they separate and she oviposits alone, while he guards his investment from the air.<\/p>\nShadow darners<\/h3>\n