There is not much going on with the Loons these days. Our pair is still together and visiting different parts of the Lake. There have been between 3 and 4 other adult Loons on the Lake recently. More late summer visitors, mostly young adult individuals, will begin congregating in advance of Fall migration.
With so much rain last year and heat this year during incubation, this is the second bad year in a row for New Hampshire Loons. Hopefully our pair will be well fed when they leave in the Fall and will come back ready to provide us with less drama and a chick or two.
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Dragonfly and Damselfly Behavior
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It is a great time of year for watching Odonata (an Order of insects including Dragonflies and Damselflies).The common name, "Dragonfly", confusingly refers to both the whole group (Odonata) and to the sub-group that have their wings fully spread at rest - Anisoptera. The other sub-group - Zygoptera - whose wings are held together or slightly spread at rest are called damselflies. Here we will use "Odonata" to refer to both groups while "dragonfly" refers to the Anisoptera and "damselfly" refers to the Zygoptera.
The abundance of dragons and damsels around the Lake gives us an opportunity to explore behaviors associated with egg laying.
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Most of the Odonata you see at the water are males. They frequent areas where females are likely to show up to mate and lay their eggs. Male Odonata spend their time perching or patrolling. Many, like the Eastern Amberwing (Perithemis tenera) above, occupy and defend a territory, trying to exclude other males from access to incoming females.
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Females, above an Eastern Amberwing, spend most of their time away from the water feeding and maturing eggs. But why not feed at the water like the males do?
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There are two good reasons to avoid spending time at the water. One is that the land-air-water interface is especially dangerous! Individuals are out in the open and exposed to aerial, terrestrial and aquatic predators - birds, frogs, fish, spiders and even other Odonata. Here a damselfly has been caught by a Tetragnathid spider, common on emergent aquatic plants.
Frogs, like the Bullfrog below with a mouth full of damselfly, are also major predators.
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But predators are just one reason for females to avoid spending too much time at the water. The other reason is male Odonata!. It is advantageous for a mated female to put her fertilized eggs in the best places for their hatching and development. Those places are also where males seeking mates are most likely to hang out and that means being continually harassed by males wanting to mate.
A female does best if she can mate and lay her fertilized eggs as quickly as possible while reducing time exposed to predators and being interrupted by males.
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Mating times for Odonata vary from several seconds to several hours. Many dragonflies, like the a pair of Blue Dashers (Pachydiplax longipennis) above, mate while perched as do all damselflies. Other dragonflies will mate in mid-air.
Like most insects, dragonfly eggs are fertilized as they are laid. A single mating will allow a female to store enough sperm to fertilize all the eggs she is carrying as well as many future batches of eggs she produces.
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How long it will take her depends on how eggs are laid. For all damselflies and some dragonflies eggs are deposited one at a time into plant tissues. Laying several dozen eggs can take a while. Below, a Forktail (Ischnura) damselfly (left) and a Green Darner (Anax junius) dragonfly are inserting their eggs into plants using a blade-like ovipositor.
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The rest of the dragonflies drop their eggs in batches above or at the water surface. Doing so, they can lay hundreds of eggs in a few minutes if not interrupted.
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A female Calico Pennants (Celithemis elisa), still in tandem with her mate, is laying eggs by dipping her abdomen in the water.
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Now that we know how female Odonata lay eggs and why they need to do it quickly and safely, let's add the male's perspective. Once mated he would also benefit from having lots of eggs fertilized by him and deposited in good places for offspring survival. How do males and females interact after mating and during egg laying to meet their individual and common goals?
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Let's start with a species that Jon has done research on for over 30 years, Ebony Jewelwings (Calopteryx maculata). Males are territorial, defending emergent vegetation that females lay their eggs in. Once mated, the female will lay her eggs while guarded by her mate.
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Above, the male is guarding a female he mated with. He will chase off intruders, giving the female more time to lay eggs. Guarded females can lay eggs about six times longer than unguarded ones. Still, egg laying females are often pounced on by other males while their mate is chasing others away.
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Other Jewelwing species, like the Superb Jewelwing (Calopteryx amata), have a different approach. They are territorial at the same kinds of emergent vegetation used by Ebony Jewelwings. However, the females lay their eggs while totally submerged, thereby avoiding males.
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They can remain underwater for more than an hour by breathing air trapped on their body (thus the silvery appearance above). Females of several other local damselfly species occasionally also submerge to lay eggs.
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The most common way for damselfly males to guard females is by remaining attached (in tandem) while their mate lays eggs. Below a pair of Spreadwing damselflies (Lestes spp.) are doing just that in Turtle Cove.
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Many dragonflies also use tandem egg laying. Kudos to Jen for capturing the pair of Calico Pennants below and the ones above flying and egg laying in tandem. No easy feat with a big lens and sitting in a kayak.
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Another strategy used by female Odonata is to lay eggs alone, either secretively or during times of the day when fewer males are around.
The Forktail damselfly female below is a secretive egg layer. The female coloration of some Forktails varies within a species, with some female morphs having very similar coloration to males. That gives those females added protection from males seeking mates.
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Some Odonata, like the Vesper Bluets (Enallagma vesperum) (below), are most active around dusk when one would expect interference to be less likely. In the photo below an ovipositing pair of Vesper Bluets (lower left) are being approached by three other males (yellow faces) showing that it does not always work.
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We hope the information above helps you appreciate some of the complexity of the dynamics among male and female behaviors in these ancient insects.
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Bye for now... Jon and Jen
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Text and Photographs by Jen Esten and Jon Waage
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| PLPA is managed by volunteers and supported by member donations. If you wish to become a member please visit http://plpa.net/membership/. |
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Ours is not the only lake blessed with loons in New Hampshire. As members and supporters of the Loon Preservation Committee, we encourage you to visit their website ( https://www.loon.org/ ) to learn more about loons and LPC's efforts and help others in the area enjoy the treasures we have here on Pleasant Lake.
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