Threatened Dragonflies: Habitat matters

Those concerned about endangered species of dragonflies often focus most of their attention to larval habitat and maintaining aquatic sites with suitable water quality. Research by a group of Czech scientists* challenges the

presumption that the dramatic decline in distribution and abundance of many dragonfly species in temperate climates since the second half of the 20th century is mainly a result of destruction of aquatic habitats, and that protection of these habitats should thus be the primary focus.*

Halloween Pennant

Halloween Pennant

They studied the habitat of adult spotted darter dragonflies, Sympetrum depressiusculum, and found that the terrestrial habitat surrounding the aquatic site could influence whether the aquatic site was suitable or not. Dragonflies were only found in areas with dense vegetation and not found in agricultural areas that were actively managed and disturbed. The dragonflies were primarily found within one kilometer of the larval sites. Efforts at conservation may require terrestrial buffers adjacent to suitable aquatic habitat.

*Dolny ́ A, Harabisˇ F, Mizˇicˇova ́ H (2014) Home Range, Movement, and Distribution Patterns of the Threatened Dragonfly Sympetrum depressiusculum (Odonata: Libellulidae): A Thousand Times Greater Territory to Protect? PLoS ONE 9(7): e100408
doi:10.1371/journal.pone.0100408

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Honey Bee Art

Dewar's Honeycomb Bottle

Dewar’s Honeycomb Bottle

The moveable frame honey bee hive uses frames with hexagonal cell templates to encourage the bees to tightly pack their cells tightly together. The hexagonal template serves as a cue to build a cell. Artists are using this bee behavior to create “bee art” objects.

One of the most publicized was a 3D Bee “Sculpture” of a Dewar’s Scotch Whiskey bottle. As part of a marketing campaign for their Highlander Honey Scotch Whiskey, Dewar’s advertising agency sponsored the creation of a template in the shape of a whiskey bottle and used the services of beekeeper, Robin Theron to create a sculpture. The honeycomb template was formed to the shape of a whisky bottle, then enclosed in with a clear outer casing to create “bee space” next to the template. Approximately 80,000 bees finished the sculpture using wax from their wax scales.

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Mayflies Monitoring Metals

Brown Drake Mayfly

Brown Drake Mayfly

May flies are sensitive to pollution of many types including heavy metals. Exposure to the zinc can have larger effects on the adults and subimagos than the larvae. Wesner and Colleagues* reared mayflies (Centroptilum triangulifer) in water with increasing concentrations of zinc from 32 to 476 ppb (parts zinc per billion parts water). Adult mortality steadily increased from 32 to 476 ppb zinc. Larva mortality decreased very slowly with concentration until concentrations reached about 200 ppb, then declined more rapidly.

Why are the adults more sensitive? Zinc concentrations above 139 ppb visibly affect wing pad development. Lower zinc concentrations may affect development in ways that are not visible or interfere with other structures. Deformed wing pads or other deformities can interfere with metamorphosis, a sensitive period with elevated mortality in mayflies. One of the ways that zinc may reduce mayfly populations is affects on successful molting.

J. S. Wesner, J. M. Kraus, T. S. Schmidt, D. M. Walters, and W. H. Clements. 2014. Metamorphosis Enhances the Effects of Metal Exposure on the Mayfly, Centroptilum triangulifer. Environmental Science & Technology.
DOI: 10.1021/es501914y

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Friday Cat-erpillar Blogging: Regurgitation

Primary-regurgitators

Red Spotted Purple Caterpillar, Limenitis arthemis astyanax, a Non-regurgitator

Some but not all caterpillars respond to attack by predators (or pinching) by regurgitating fluid from the digestive system. JB Grant compared* the response of 36 caterpillars of butterflies and moths to simulated attacks (pinching). Caterpillars varied in their response and were grouped into 3 categories.

1. Primary-regurgitators responded immediately to attack by directing regurgitant at the site of attack. They could control the amount of fluid expelled: a little for a weak pinch; more for a harder pinch. Fluid was re-ingested after the defensive response ended.
2. Secondary-regurgitators first exhibited an alternate defense such as flailing, biting and escape. Regurgitant oozed from the mouth, not in a distinct droplet.
3. Some caterpillars, such as the red spotted purple never regurgitated.

Grant measured the lengths of the crop, midgut and hindgut and found that the relative lengths varied and were correlated with regurgitation defense. Primary-regurgitators had the longest relative crop and shortest relative midgut. Non-regurgitators had the shortest relative crop and longest relative midgut. Secondary-regurgitators were intermediate. The hindgut did not vary with behavior. Caterpillars that use regurgitation for defense may have adaptations to the crop and foregut that provide better control of regurgitation and a larger pool of regurgitant.

*Grant, JB. 2006. Diversification of gut morphology in caterpillars is associated with defensive behavior. The Journal of Experimental Biology 209, 3018-3024.
doi:10.1242/jeb.02335

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Emerald Ash Borer In West Lafayette

A few years after Emerald Ash Borer was first reported in Tippecanoe County noticeable damage is becoming widespread. Prior to this year, there were isolated damaged trees. Now the effects on the landscape are readily apparent. The image below was taken on August 27, 2014 in a strip mall parking lot near US 52 and Salisbury Street in West Lafayette. All of the ash trees are dead or dying. The trunks and branches are riddled with D-shaped exit holes (Inset). Most of the trees in this lot are tagged for removal.

Emerald Ash Borer imposes economic costs and aesthetic costs. Shoppers like to park in the shade in summer. Now the shade is gone. The trees in this lot are not the only ones affected. Many of the ash trees on US 52 are starting to show decline. Cities throughout Indiana must decide whether to treat and save some ash trees or remove and replace. West Lafayette has a program to replace the ash trees on city property with other tree species over a five year period. Perhaps a solution to EAB will be found. For West Lafayette, the hour is late.

Ash Trees

Ash Trees in Decline Due to EAB
Inset: EAB D-Shaped Exit Holes

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Beetle Check

Asian LongHorned Beetle

Asian LongHorned Beetle
Image: Donald Duerr, USDA Forest Service, Bugwood.org

Invasive species move into a state most frequently from a neighboring state.  It follows that the highest risk for invasion comes from large populations of an invasive near the border.  The Asian Longhorned Beetle (ALB) can be found in the Cincinnati area, a few miles from the Indiana border. Governor Pence is asking Indiana residents to check for signs of the beetle.

How can you help? Asian Longhorned Beetles are wobbly fliers that sometimes land in swimming pools and become trapped in the filters. Swimming pool owners or managers can check the filters and report any large beetles that look like ALB to the state. The ALB prefers maples. Homeowners can check maple tress for large exit holes or burrows. (The little holes in rows are made by sap suckers. They are not ALB). If a hole is suspicious, collect the frass. It can be analyzed for ALB DNA. Previously healthy maples that show signs of decline are worrisome and should be inspected.

If ALB is found, your tree will be removed. The tree will not have long to live and their is no good treatment. Don’t move untreated hardwood firewood in the Cincinnati area. Beetles can be hiding in the wood and moved to a new area. The beetle is often found in the tops of trees, making inspections difficult. Until better monitoring methods are developed the best defense against ALB is an informed and alert public.

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Golden Digger Wasp

Golden Digger Wasp

Golden Digger Wasp

The Golden Digger Wasp, Sphex ichneumoneus is a large wasp that is seen collecting nectar from flowers along side the Big Black Wasp. It is distinctive as a large wasp (about 20 mm) with golden to orange body and legs. It has rows of yellow hairs on the back of its head and the top edges of its thorax.

This wasp hunts large insects, primarily crickets, katydids and grasshoppers that it places in a underground nests as food for its offspring. Typically, there are several chambers radiating from a common point. This has been a good year for crickets and grasshoppers in Indiana. The wasps should have good hunting.

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