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


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.

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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,

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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The Great Black Wasp

Great Black Wasp

Great Black Wasp

Sphex pensylvanicus, has a descriptive common name, the Great Black Wasp.  This conspicuous wasp is 22 to 28 mm long (females are larger) and are commonly seen on milkweed and other sources of nectar.  The wasp is mostly black with an iridescent blue color on the forewings.  The tips of the wings are black.

This giant wasp digs a tunnel for her offspring and provisions the nest, typically with katydids.  Many of the katydid prey are larger than the wasp.  Katydids are immobilized with wasp venom and flown back to the nest.  A single immature may require multiple katydids to complete development.  The tunnels are about a half meter long.  After the female provisions a cell with food and lays a single egg, the chamber is sealed and another begun in the same tunnel.

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Streaming Insects

Bug Zapper

Bug Zapper

The world needs energy production that does not increase atmospheric carbon dioxide concentrations and cause climate change. Innovative new solar and wind designs are being built at a commercial scale. One solar design in the Mojave Desert uses mirrors to reflect light onto a tower. The light heats the tower and the collected heat boils water, generating steam that can drive electricity generating turbines. The good news: Once built, the plant has no costly fuel inputs (sunlight is free) and is relatively low maintenance.

The bad news: The plant can kill birds and insects. As a child, I played with magnifying glasses, focusing sunlight on leaves or scraps of paper until they burned. The solar plant can have similar effect, burning creatures that fly through the area. Bits of debris, insects and birds traveling through the reflected sunlight can ignite, smoke marking their flight path. The workers call these burning objects “streamers” after their smoke plumes. Small insects are carbonized by the encounter. Some birds are killed; others may burned in ways that impair flight.

There is much concern about the birds, but little concern about the insects. The number and species of birds killed by the plant has not been measured, but may be significant. The area is too large to erect physical barriers to the birds. Bird deterrents such as visual markers and sound are being investigated. The number of insects killed is unknown and no attempts to quantify the number or exclude insects from the area are under consideration. Probably far more insects are killed from collisions with cars and trucks on a busy highway than are affected by the solar plant.

No technology is free from problems. The human structures that kill the most birds continue to be windows. The bird deaths from colliding with windows in buildings are perhaps less of an issue because they are dispersed and not concentrated in one place that becomes a focus of attention. Visual patterns in windows can prevent many bird collisions, but they are not widely adopted or mandated. The bird kill problem may need to be solved if the solar tower technology is to continue in use.

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