Photo: Thierry Heger
The kissing bug, Rodnius prolixus,
feeds on the blood of mammals including humans. It is called the kissing bug after its habit of feeding on saliva. Rhodnius requires a blood meal in each immature stage. Laboratory studies of Rhodnius have elucidated some of its feeding secrets. How does a bug decide whether or not to feed?
Rhodnius has a sucking tube that it can use to sip saliva from the skin surface or stick into the skin to drink blood. It will also feed on artificial solutions in the laboratory. Liquids are pumped by the pharynx into the insect. As the liquid passes the pharynx, it passes taste receptors responsive to nutrients in the liquid. The energy molecule, ATP, is detected and will act as a feeding stimulant. Receptors measure the concentration and ratios of sodium and potassium salts in the liquid. Only salt concentrations between 0.1 and 0.15 M trigger feeding. This is the concentration range of these salts in blood. Liquids with high salt concentration (> 3M) are rejected as are liquids that lack salts. Salts are monitored continuously during feeding. A sudden change in salt concentration outside the acceptable range will terminate feeding.
Rhodnius depends on blood for survival. It has evolved receptors and sensory feedback that trigger feeding on liquids that mimic blood and reject liquids that are not similar enough to blood. Rhodnius is adapted to engorge on blood but drink little of other liquids.
Gina Pontesa, Marcos H. Pereirab & Romina B. Barrozoa. Salt controls feeding decisions in a blood-sucking insect. Journal of Insect Physiology Volume 98, April 2017, Pages 93–100.
Soldier Fly Larvae In Compost
Black soldier flies are attracting substantial interest for their activity as composters, animal and fish feed. Livestock operations have waste that attracts nuisance flies. Black soldier flies can compete for the same food but are not pests as adults. Replacing the population of pest flies with black soldier flies would be helpful to livestock operations.
Black soldier flies are common in the warm temperatures of summer but do less well in cooler temperatures. Maintaining soldier flies year round requires providing the adults flies with suitable conditions for mating during cold winter months. Black soldier flies mate in the air and require a substantial flight space. They are sensitive to light and temperature, preferring direct sunlight and temperatures between 70 and 80. Anecdotal success stories can be found online but are not necessarily successful for everyone. A more rigorous study of mating conditions for black soldier flies would be appreciated by many fans of this insects.
Drawing of Manduca Life Stages Artist: Maria Sibylla Merian
The printing press made images widely available to the public in the 17th century. Drawings of animals were popular, especially those that accurately captured details of insect life history. Drawings such as the one at left convey information about lifecycle, metamorphosis and host plants. Images readily cross language barriers. This painting by a German, Maria Sibylla Merian, living in The Netherlands is readily understood by Americans today without translation.
By the 17th century, the idea of spontaneous generation had been rejected by the educated classes. Insects were no longer believed to arise spontaneously from mud or rotting meat. If insects did not arise from mud, how do they form? A new narrative was needed. The beautiful life cycle illustrations promoted a richer and more compelling story. It allowed people to share these fascinating life history stories with others and spread important information about insect biology.
Long Legged Fly
The heads of insects are orders of magnitude smaller than the heads of even the smallest mammal. Many functional organs and tissues must fit in a limited space. The cuticle covering the compounds eyes doubles as both lens to focus light and part of the structure of the head. Insect eyes are fixed, do not move and have no musculature. These features save some space inside the head.
The head contains muscles responsible for the movement of the antennae and mouthparts. The head has invaginations of the exoskeleton that serve as anchors for those muscles. Food intake must pass through the head. The digestive system in the head consists of a pharynx and esophagus. In sucking insects, the pharynx [food pump] may occupy a substantial area. The esophagus is a tube where food passes out of the head and into the more spacious abdomen where the large digestive organs are located. In some insects, salivary glands are located in the thorax and abdomen with only thin ducts inside the head. These structures all claim space and this limits the volume available for the insect brain.
Cells in all organisms are of similar size. Thus, an insect, with less space for brain cells than mammals will have far fewer brain cells. Their small head size requires insects to use the limited number of brain cells more efficiently.
Halloween Pennant Dragonfly
Insect wings are flexible without being flaccid. They change shape when air pressure is applied. The ability to bend the wings can change the direction of pressure forces on the wing. Flexible wings can bend in ways that improve thrust without input of extra energy. The flexible wings of a dragonfly are far more efficient than if the wings were stiff.
Engineers are interested in applying the lessons of flexible dragonfly wings to wind generators that use the power of the wind to rotate turbine blades. A group of engineers* created small scale turbine blades with no flexibility, high flexibility and moderate flexibility. The high flexibility blades performed poorly. However, the moderately flexible blades were up to 35% more efficient than blades with no flexibility.
This research has interesting possibilities. One of the issues is how to scale these results to large power generators of the type now in use. The very large blades must maintain their integrity under a variety of stressful conditions. A material with appropriate combinations of strength and flexibility will be a key to making these findings useful.
*V. Cognet, S. Courrech du Pont, I. Dobrev, F. Massouh, B. Thiria. Bioinspired turbine blades offer new perspectives for wind energy. Proceedings of the Royal Society A. February 17, 2017 http://rspa.royalsocietypublishing.org/
Placing Bee Hives in an Almond Orchard
California almond trees are in bloom from February through early March. To produce an almond, each flower must be visited by a honey bee or other pollinator. It is estimated that as many as two thirds of all the commercial bee hives in the US are now located in the almond orchids. The bees contribute so much to the almond crop that growers pay between $100 and $200 per hive. Large commercial beekeepers sign contracts to deliver bees. They shut their bees in at night, stack the hives on pallets and drive the hives to almond country on flatbed trucks. At the orchard, pallets are removed by fork lifts and spread through out the orchard. The bees are released in a sea of almond pollen and nectar. In March when the almonds finish blooming, beekeepers pack up their bees and transport them to other locations where pollen and nectar are available.
This system of pollination is needed because almond orchards are kept clean of “weeds” that could harbor tree pests. Alternative sources of pollen and nectar are not available in large enough quantities to maintain the numbers of pollinators needed at peak almond bloom. The bees must leave in March because there is no longer enough food.
This system is economically lucrative, but places stress on the bee colonies. Bringing bees to a small area allows diseases and parasites to spread among the hive. Insecticides are not used during pollination season to protect the bees. However, the areas where bees go after almond pollination are not uniform or uniformly managed. Some crops within a mile radius of a bee hive may be treated with insecticides that could harm bees that visit there. This system has incurred substantial losses of bee colonies every year that most be replenished to maintain the system. There are many challenges to keeping bee colonies healthy under these conditions. Bee biologists are studying when, where and why colonies are lost, hoping to reduce the losses of bee colonies.
Worker Honey Bee
Honey bees do not prefer their water too clean. Like many herbivorous insects, honey bees do not get enough sodium by eating pollen and nectar. They prefer water that contains sodium over deionized water. Sodium is commonly found in mud puddles.
Dietary concentrations of calcium, magnesium and potassium are found in pollen. Bees do not seek these minerals when pollen is abundant. However, in autumn when pollen can become scarce, bees will seek these minerals from open water sources.
RACHAEL E. BONOAN, TAYLOR M. TAI, MARLEN TAGLERODRIGUEZ, LAINE FELLER, SALVATORE R. DADDARIO, REBECCA A. CZAJA, LUKE D. O’CONNOR, GEORGIANA BURRUSS & PHILIP T. STARKS. Seasonality of salt foraging in honey bees(Apis mellifera) Ecological Entomology (2016),