Image by Sarah-fiona Helme

'Summer Stripes,' a finalist in the International Garden Photographer of the Year competition.

This stunning image shows a flower fly (or hover fly, as it is commonly called in the United Kingdom) on a gazania flower.

Last week was national pollinator week here in the United States, but it’s always a good time to discuss the importance of pollinating insects.

Flower flies live on every continent except Antarctica and are pollinators of major economic significance. “In some agroecosystems, such as orchards, they outperform native bees in pollinating the fruits,” according to the U.S. Department of Agriculture.

Flower flies look like wasps and bees, but can’t sting. This is a great example of Batesian mimicry, where a harmless species imitates a harmful species. In this case the harmless flower fly has evolved coloration that mimics the more dangerous stinging wasp or bee. The flower fly looks like a stinging insect, hopefully deterring predators, but without expending energy on developing and maintaining a stinger.

Congratulations to photographer Sarah-fiona Helme of South Lanarkshire, Scotland, who captured this image in her garden. Her photograph was a finalist in the 2009 International Garden Photographer of the Year competition.

‘Summer Stripes’ is on display at Kew Gardens near London until September 13, 2009.

California’s almond growers, which produce 80 percent of the world's supply, are facing a bee shortage.

June 22 - 28 marks National Pollinator Week, when we “appreciate the hard working  animals that help pollinate over 75 percent of our flowering plants and nearly 75 percent of our crops,” according to the U.S. Fish and Wildlife Service.

Flowering plants require pollination, the transfer of pollen grains between flowers of the same species, in order to reproduce and bear fruit. Birds, bees, bats, butterflies, moths, beetles and even the wind transfer pollen among flowers.

Honeybees in particular are central to pollination. Farmers frequently rent commercial honeybee colonies: bee colonies are driven to the farms, allowed to pollinate crops and then removed. Commercial colonies can be driven around the country to pollinate multiple farms.

One of the primary causes of honeybee death worldwide is Colony Collapse Disorder (CCD), characterized by a nearly complete absence of adult bees with little or no dead bees in and around the colony. Without adult bees to work, the colony is doomed to collapse.

Scientists are unsure as to the causes of CCD. A 2007 study found a correlation between collapsed colonies and infection with the Israeli acute paralysis virus, a virus of unknown origin first identified in Israel and found throughout the world. However, researchers did not show that the Israeli acute paralysis virus causes CCD.

In February, scientists in Spain reported two cases of apparent CCD associated with a parasite infection (the microsporidium Nosema ceranae). No other significant pathogens or pesticides were detected, but this is not proof that Nosema infection causes CCD.

Perhaps a combination of factors, such as poor nutrition, pesticide exposure and mite and viral infections leads to CCD.