Picture on the Wing

Black Onion Fly

Black Onion Fly

The Black Onion Fly, aka the Onion bulb maggot, Tritoxa flexa, has been reported in North American entomological publications dating to the 1865. The black onion fly is mentioned as an occasional pest of onions that can cause some damage to the bulbs, but has never been elevated to “serious” pest status.

The flies are known as “picture wing flies” of the family Ulidiidae (formerly placed in Otitidae and Ortalidae). The wings have interesting patterns which possibly have a role in mating and mate recognition. These flies are not uncommon in gardens of the Midwest where onions are grown. They will land on flat surfaces holding their wings like oars to display the charming patterns.

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Cleaning Bees

From the NYTimes:
https://static01.nyt.com/video/players/offsite/index.html?videoId=100000005089002

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Spinning Silk

Spider web

Web of Stegodyphus Social Spiders
Photo: Dr VB Whitehead

Major ampullate silk is secreted by the major ampullate gland of spiders. In the best studied systems two silk proteins differing in amino acid sequence and structure are secreted by the gland. The ratio of the two proteins is thought to affect the silk properties.

MA silk is produced in the MA gland which has a distal tail, a storage reservoir, and a duct to the outside that ends at a spigot to control release.  Silk proteins are secreted by cells lining the narrow tail of the MA gland. The proteins are stored in the reservoir at a pH between 6.8 and 7.0. pH affects the folding and structure of proteins. When a silk strand is released, protein from the reservoir travels down the duct to the spigot.  Within the duct the  pH of the silk solution acidifies from a neutral pH at the reservoir end to an acidic pH of about 5 near the spigot. The change in pH helps the silk to assemble into strands when they are released from the spigot.

Vollrath F, Knight DP. 2001. Liquid crystalline spinning of spider silk. Nature 410:541–48

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Celebrating Insects and Culture

Mealworm Stir-fry

Mealworm Stir-fry

In mid April, Mexico City has the Festín de Insectos Comestibles. Over 5 thousand people visit to taste the roasted maguey worms, crispy beetle bonbons and mosquito-egg tacos. The festival offers a chance to recognize the folk wisdom of women from the campo, whose gastronomical knowledge was passed down generationally.  More than 500 species of insects were eaten as part of the Meso-American diet.  Many visitors tasted insects as cuisine for the first time.

People from a Meso American culture tradition observe a change in attitude. Their cuisine is not new, but it is new to modern Mexican culture.  During the 50s and 60s, the dominant culture frowned upon entomophagy and traditional Meso American foods. Many look back at those efforts as a racist campaign to scorn the traditional foods and culture and impose commercial foods. Times change and so do attitudes. Far from the disparagement of the past, in our current era many people are reacting positively, curious about how the bugs are foraged and prepared, and ready to pay for the privilege of eating them.

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The Complexity of Silk

Spider web

Web of Stegodyphus Social Spiders
Photo: Dr VB Whitehead

Strands of spider silk are not a simple uniform material and are far more complex than plastic fishing line. Plastic fishing line is a solid, uniform entity. A strand of spider silk is an organized structure built from small units.

When we observe a strand of spider silk, we only see the outer skin. The outer skin is composed of glycoproteins. Inside this visible layer is an inner skin that is rich in lipids.

The skins surround and contain bundles of independent fibers (think or a box of spaghetti: spaghetti=fibers; box=skin). An individual fiber in a bundle is not a simple uniform material. Fibers are ordered assemblies of silk proteins. At least 2 of the silk proteins have been characterized and they have similarities and useful differences. The quality of the fibers and thus the quality of the silk depends on the types of silk protein, their ratio and their arrangement. Protein mix and match results in strands with a potentially large diversity of properties.

Arthropods assemble silk on a nanoscale with cells being the unit of protein and lipid production. The silk fibers self assemble in a nanoscale environment and are joined and bundled at a larger scale. We can produce buckets of spider proteins at a very large scale. However, the interactions of the proteins and their self assembly are different at the much larger scale of a test tube. To manufacture synthetic spider silks will require developing appropriate tools at the nano-scale.

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Living With Spider Silk

Funnel Web: Agelenopsis species

Funnel Web: Agelenopsis species

Spiders produce a variety of silks that can be classified into 7 distinct types: Major Ampullate, Minor Ampullate, Pyriform, Aciniform, Flagelliform, Tubuliform and Viscous Aggregate. The silks are produced in separate glands for special purposes. Major Ampullate silk is used in the radii (spokes) of orb web spiders and as a safety line in other spiders. The Minor Ampullate silk is used for prey wrapping.

Flagelliform silk is used in the axial strands of webs. Compared to the Major Ampullate silk, it is not as strong but is more extensible. When prey flies into the web, the strands stretch to gently slow the speed and allow the prey to stick to the web instead of bouncing. To facilitate prey capture, the axial strands may be coated with gooey Viscous Aggregate which provide greater contact area with the prey.

Pyriform silk is used to attach and anchor webs to objects and can glue silk strands together. Aciniform silk is used to construct egg sacs and wrap prey. Its considerable stiffness us suited to these uses. The outer coating of the egg sac is typically Tubuliform silk.

Silk is a multipurpose material. Different silk proteins can give silk unique properties adapted to the needs of the spider. Studies of silks are useful for producing biomimetic materials.

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Living With Leishmaniasis

Sand Fly

Sand Fly Photo:

Visceral leishmaniasis is transmitted by biting phlebotomine flies (aka sand flies). The disease is spreading to urban areas in parts of Brazil.  Leishmaniasis is a neglected disease in countries such as Brazil because the disease mostly affects poor people with limited access to health care professionals.

The primary agent that causes visceral leishmaniasis, Leishmania infantum, can infect dogs. Infected dogs may be asymptomatic and therefore go untreated. A fly that bites an infected dog can transmit the disease to a nearby human.  This makes dogs ownership a risk factor for the disease.

Leishmaniasis can be cured with antibiotics. If left untreated, it can cause severe medical problems that are potentially lethal.  Prevention efforts typically focus on 2 points in the transmission cycle. The first first is to reduce the population of phlebotomine flies. The second is the use of personal insect repellents to prevent the flies from biting people. People with dogs that go into areas with uncontrolled sand flies should take extra precautions to prevent phlebotomine fly bites.

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