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Odonata

Shadow Darners Laying Eggs

9-4-17 darner laying eggs2 049A4462

The dragonfly family Aeshnidae consists of strong-flying dragonflies called darners, some of which are over three inches in length.  The majority of darners reach the peak of their population in August and early September.  Male Shadow Darners (Aeshna umbrosa) can be seen patrolling breeding sites a few feet over the water’s surface, searching for females and driving off competing males. Females can be observed repeatedly landing at the base of cattails, inserting their sharp-edged ovipositors and slicing open leaves, where they then deposit their eggs.  If you look at the bottom third of cattails at this time of year, near the water’s surface, you will find tiny, tan, vertical slits where dragonfly egg-laying has taken place. (Photo:  female Shadow Darner laying eggs)

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Common Green Darners Appearing

6-20-17 common green darner 021The Common Green Darner (Anax junius) is one of our most common dragonflies. often seen near ponds. The family of dragonflies known as “darners” consists of species with large eyes and long abdomens that tend to rest infrequently and when they do rest, usually hang vertically. The Common Green Darner is the only North American darner in which the male and female usually fly in tandem when the female is laying her eggs on emergent vegetation.

Up to 50 of the world’s 5,200 dragonfly species migrate and the Common Green Darner is one of them. In the fall most (but not all) adult Common Green Darners migrate south to Florida, eastern Mexico and the West Indies. Huge clouds of migrating dragonflies have been seen along the East Coast, Gulf Coast and the Great lakes in autumn. Transmitters weighing 1/100th of an ounce that have been attached to migrating dragonflies confirm that they migrate much like birds. Just like avian migrators, they build up their fat reserves prior to migrating; they follow the same flyway as birds, along the Atlantic Coast; and like birds, dragonflies don’t fly every day but stop and rest every three days or so.

Some dragonflies mate and lay eggs along the way, while others do so when they reach their destination. The eggs hatch, larvae develop and the adults head north in the spring. Unlike birds, migration is only one-way for dragonflies. It is the offspring of the fall migrating generation that migrate north in the spring. Here in the Northeast, most arrive before any resident Common Green Darners have emerged. (photo:  female Common Green Darner)

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Damselfly or Dragonfly?

6-16-16  damselfy & dragonfly 178A visit to a pond will usually include sightings of dragonflies and the more delicate damselflies.  Both of these types of insects are in the order Odonata (Greek for “tooth,” referring to the serrated jaws of the adults).  They are separated into two suborders, due to their wing shapes and sizes. The wings of dragonflies differ in shape and size (hind wings are broader than forewings), whereas damselfly fore and hind wings are similar in shape, with the hind wings sometimes being smaller.

In addition to wing differences, damselflies have eyes that are separated by more than an eye’s width, whereas dragonfly eyes either touch or are separated by less than an eye’s width.  Damselflies are smaller and more slender than dragonflies and perch with their wings closed over their abdomens or held slightly spread.  Dragonflies at rest hold their wings out flat or downward.  In addition, dragonflies are more powerful and acrobatic in flight than damselflies.

Although these differences distinguish them, damselflies and dragonflies do have many similarities. Both are carnivorous, both spend most of their lives as aquatic larvae, and both lay their eggs in or near water.

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Dragonflies Eclosing

5-26-16  dragonfly eclosing2  347 The sudden hot weather seems to have triggered a mass emergence of dragonflies and damselflies.  The emerging vegetation along the shores of ponds is covered with larval Odonates (members of the order of insects that includes dragonflies and damselflies) metamorphosing into adults.  The adults, still in the skin of their last larval stage, crawl out of the water, climb up vegetation, rocks, etc., and split the back of their larval skin.  The adult flips backwards out of this opening, hangs upside down and then grasps the vegetation and/or empty larval skin while as its abdomen is released.  The dragonfly hangs in the breeze while it pumps air into its body, sending liquid into its wings.

To appreciate this process called eclosion, compare the size of the wings in the photo insert (recently-emerged adult) with those in the larger photograph, which was taken twelve minutes after emergence.  Within a day or so the sheen on the newly-formed wings goes away, the dragonfly’s body hardens and colors start to appear.

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Darners Laying Eggs

9-1-15 dragonfly laying egg 135Females of different species of dragonfly have different techniques for laying their eggs. Most skimmers, cruisers and clubtails dip the tip of their abdomen to the surface of the water while hovering or flying, and release their eggs. Most darners, such as the Shadow Darner (Aeshna umbrosa) pictured, have a sharp-edged ovipositor with which they slit open a stem or leaf of a plant on or near the water. They then push their egg into the plant tissue exposed by the slit. Because they are stationary during this process, female darners are vulnerable to predation by fish and frogs at this time. A close look at the bottom third of cattail leaves this time of year will tell you whether or not darners are in the vicinity, as the slits they make are very apparent, appearing as thin, tan, 1/2″ vertical lines.

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Dragonflies & Damselflies Spear Prey With Lower Lip

7-27 dragonfly mouthpart 077Dragonflies and damselflies are unique among aquatic insect larvae in that they have a greatly enlarged hinged lower lip, or labium, which they can rapidly extend outwards to capture prey. When retracted, the prehensile labium fits like a mask over the face or is folded flat beneath the insect’s head. When hunting for prey, the dragonfly larva uses its labium like a speargun. It shoots forward as far as half the larva’s body length away, and moveable hooks on the front edge grab the prey. There are no muscles at the hinge/joint, leading entomologists to believe that the labium is extended by increased blood pressure caused by abdominal muscle contraction. It unfolds at a right angle, and extends extremely rapidly, faster than most prey can react. (photo: cast skin of dragonfly larva from which adult dragonfly emerged)

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Meadowhawks Mating & Laying Eggs

9-30-24 autumn meadowhawks laying egg  043There is a genus of dragonflies, Sympetrum, referred to as meadowhawks, which emerge and fly in late summer and autumn, breeding in ponds and foraging over meadows. Mature males and some females of certain species of meadowhawks become bright red on part or all of their bodies. When breeding, the male grasps his mate behind her head with the appendages at the end of his abdomen and often does not release the female until after she has laid her eggs, which she typically does by dipping the tip of her abdomen in the water (see photo). The reason for this continued connection is related to the fact that a male dragonfly may remove sperm present in the female from any previous mating and replace it with his own packet of sperm, or spermatophore. In order to prevent this from happening, and to assure his paternity, a male dragonfly sometimes flies close to his mate, guarding her while she lays her eggs, or, in the case of meadowhawks, may fly in tandem with the female throughout the egg-laying process.

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