Monthly Archives: October 2015

What is Climate Change doing to our Bees?

Insect pollinators ensure transfer of genetic material between plants (sexual reproduction) and maximisation of fruit sets and yields. However these beneficial insects are in decline worldwide, owing to the intensification in crop production of the 20th century (giving less diverse forage), misuse of pesticides and proliferation of various diseases. A driver of decline still under contention is global warming (more accurately climate change) as the effects are hard to predict and will be different for specific groups of pollination- an optimum foraging temperature for bees may be not be so good for pollinating moths, butterflies, hoverflies or birds.

Temperature too high?

Many insects are ectotherms, meaning they do no generate their own heat and need to bask in the sun to become warm enough. Pollinator groups such as butterflies have their distributions limited by low temperatures at high latitudes, so when the climate warms in these areas the generalist species (those that may feed on a wide breadth of flowers) are expected to expand their distribution northwards, but a colder winter temperature will cause their range to recede southwards. For bumblebees the relationship is not as clear- some species have retreated northwards (Bombus distinguendus) and others have retreated southwards (B. sylvarum). Other problems may arise for bumblebee queens that overwinter and emerge from dormancy to find their newly-found colonies is out of sync with their forage plants- this is known as a phenological mismatch or phenotypic asynchrony.

Out-of-sync with host plants?

Climate change is causing phenological advances (a delay) of flowering in plants which means insects have a shorter foraging season to feed and raise their young (either by feeding larvae or provisioning resources to eggs). Non-Apis bees (bees other than honeybees) in particular are shifting in relation to their host plants, with their queens even emerging from overwintering to find very few nectar plants have flowered yet, suggesting no clear pattern for phenological mis-matching. But some researchers argue that in robust pollinator networks there is an assemblage of multiple plant species for early emerging or late emerging pollinators to feed on, and vice versa. For specialist pollinators there is also a risk of spatial mismatches, where plants offering nectar and pollen shift their range and distribution much to the chagrin of specialist pollinators that must ‘track’ their host plant by migration (but this depends on dispersal ability, commonness of preferred nesting habitat). Generalists, however, will be able to take advantage of biodiversity of forage plants and will be affected less. In response to pressures to alter their diet, some bee species have even been rapidly evolving shorter tongues in order to feed from plants with shallower corollas. In 40 years, 2 alpine species of bumblebee (Bombus balteatus and B. sylvicola) have reduced their tongue length by 3 millimetres in response to a 60% decline in flower production.

Pollinating-moth-feeds-from-Sacred-Dutura

Exacerbating other drivers of decline?

Climate change may interact synergistically with other causes of declines, for instance increased temperatures may speed up pathogen growth rates and lead to increased proliferation of bee parasites, such as varroa mite. Climate warming is speculated to increase the competition for resources between native bees and invasive ‘super-generalists’, possibly leading to extinction by competitive exclusion. Climate change may also cause development of agricultural methods that have an adverse effect on bees, such as devoting more land to growing crop monocultures (reducing florally diverse habitats) or increased use of pesticides.

What can be done?

Efforts are being made to help sustain pollinator diversity in agricultural landscapes, such as the compulsory planting of wildflowers through environmental stewardship schemes. However some researchers argue the existing biodiversity of food plants will ensure plant-pollinator phenological synchrony against climate change, and only very specialist feeders will be at risk. The rapid evolution of some at-risk bee species (such as those with shorter tongues) will also play a key role in recovery of pollinator populations. Efforts to mitigate the effects of climate change (such as reduction of emissions and geo-engineering solutions) would also reduce the subsequent effects on pollinator decline.

Further Reading:

Bartomeus, I., Ascher, J. S., Wagner, D., Danforth, B. N., Colla, S., Kornbluth, S., & Winfree, R. (2011). Climate-associated phenological advances in bee pollinators and bee-pollinated plants. Proceedings of the National Academy of Sciences108(51), 20645-20649.

Burkle, L. A., Marlin, J. C., & Knight, T. M. (2013). Plant-pollinator interactions over 120 years: loss of species, co-occurrence, and function. Science,339(6127), 1611-1615.

Garibaldi, L. A., Steffan-Dewenter, I., Winfree, R., Aizen, M. A., Bommarco, R., Cunningham, S. A., … & Klein, A. M. (2013). Wild pollinators enhance fruit set of crops regardless of honey bee abundance. Science, 339(6127), 1608-1611.

Miller-Struttmann, N. E., Geib, J. C., Franklin, J. D., Kevan, P. G., Holdo, R. M., Ebert-May, D., … & Galen, C. (2015). Functional mismatch in a bumble bee pollination mutualism under climate change. Science349(6255), 1541-1544.

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News Roundup: Autumn 2015.

Disease eradications, Bee vaccinations and Entomophagy- catch up on all the latest entomological news stories you might have missed!

Risks of Eating Insects


The European Food Safety Authority (EFSA) have recently published a report on using insects as a protein source for animal feed and human consumption. It found that edible insects could contain biological and chemical contaminants, depending on how the large scale insect farms were managed.

With an estimated global population of 9 billion by 2050, using insects as a high quality source of protein as feed (for chickens, for example) could give a much needed food conversion rate (lower levels of initial energy and water required). Insect meat is also a quality source of fat, fibre, minerals and vitamins.

It is estimated that insects such as flies, moths, mealworms and crickets/locust already form the diet of at least 2 billion people. There is still clearly a way to go until western cultures can adopt new foodstuffs and a better understanding of the hazards of eating insects is required for the next step.

GM Mosquitoes trial reduced Dengue by 95%

A trial where scientists released thousands of ‘friendly’ Aedes aegypti mosquitoes infected with a bacteria that will intended to suppress dengue fever has yielded positive results. The theory was that the genetically modified yellow fever carrying mosquitos breed with the existing population and become the dominant type, thus eliminating the disease spreading variants.

The results of the Oxitec trial in Brazil found that the disease carrying mosquito number were reduced by 95%, well below the disease transmission threshold. The control was species-specific, and the Oxitec male mosquitoes mate with the naturally occurring females of the population and their offspring die before they can transmit the disease.

New methods of pest control like this are crucial as Aedes aegypti is developing resistance to insecticides and removal of breeding sites leads to them re invading the following year from neighbouring habitats that are inaccessible to us. There is also no vaccine or specific medication currently for dengue, chikungunya or zika virus (3 debilitating mosquito-borne diseases) so the development of new methods is crucial.

Honeybees give each other Vaccinations

Once a disease takes hold of a hive, the workers of a honeybee colony become disorientated and fail to forage to feed their sisters and brood. Luckily bees naturally immunize their young against certain diseases found in their environment, and scientists have recently discovered how exactly they do this.

The latest research suggests that the queen is fed on royal jelly from pollen infected with bacteria, and these are digested in the gut and stored in the queen’s fat body. Pieces of the bacteria are then bound to vitellogenin (a blood protein) and this is carried via blood to supply developing eggs with immunity.

The industries relying on honeybees colonies and the pollination service could benefit if a similar vaccine was produced for other bee diseases- like american foul brood. The discovery of vitellogenin, the carrier of immune-priming signals, could have implications for other animals that pass on immunity to their young.

Wasps are an indicator for environmental decline

A decline in wasps is thought to be a reaction to the increased harm of pesticides on wasps, and their food resource. Wasps play a key role in ecosystems (a ‘keystone species’), and taking them out would cause many systems in an ecosystem to collapse- for example dead insects and detritus would accumulate, with pestilent flies possibly taking advantage of this and proliferating.

A possible decline in wasps that might go unnoticed is what’s called a ‘shifting baseline syndrome’, meaning that small declines in number each year might go unnoticed, despite a reduction in 50% of population over 20 years (for example).

For the 2 most recognizable species of social wasp, Vespula germanica and Vespula vulgaris, there have been reported losses in number and this has been attributed to a reduction in their food resources- wasps are carnivorous during colony development (eating dead insects, aphids, etc.) and take advantage of sugar foods (such as fermenting fruit) late in the season. The decline of wasps could therefore be a signal that insects lower in the food chain are vanishing too and endangering whole systems. Environmental decline should be indicated by more than just a decline in wasps, though!

Further Reading:

Entomophagy http://www.bbc.co.uk/news/science-environment-34476742

Dengue Mosquitos http://entomologytoday.org/2015/07/03/genetically-engineered-mosquitoes-reduce-population-by-95-percent/

Honeybee Immunization http://entomologytoday.org/2015/08/03/researchers-discover-key-to-bee-vaccination/

Wasps and Ecosystems http://www.independent.co.uk/voices/nature-studies-fewer-wasps-to-swat-is-a-sign-of-an-ecosystem-in-serious-trouble-a6680881.html