Leafcutting Bee

In 1976 I received my Doctorate degree from Utah State University after completing my research on the biology and management of the Alfalfa leafcutting bee,  Megachile rotundata, since completing my degree I have spent 38 years as a recognized authority on this little bee.  First a little bit of information on the biology and management of this bee.  My web site on bees is www.pollination.com

Biology The alfalfa leafcutting bee (Megachile rotundata) is a solitary bee that makes its nests in preexisting holes. Unlike the honeybee, the leafcutting bee has no queen or division of labor. The leafcutting bee is smaller than the honeybee, about 3/8” in length. Each bee fends for itself though they are gregarious. The female uses leaf pieces that they cut with their sharp mandibles to line their nests. The bees collect pollen and nectar and pack it into a doughy ball into which they lay their eggs. While honeybees load pollen onto their hind legs, the leafcutting bees brush the pollen onto the underside of their abdomen where stiff hairs hold the pollen. In the life cycle of the alfalfa leafcutting bee there is typically one generation per year, but can have two or three generations in warmer climates, such as in California. The leafcutting bee overwinters as a mature larva inside a cocoon made of silk and covered in leaf pieces. The leafcutting bee female has a stinger and will use it to defend herself. However, the leafcutting bee is not aggressive and does not defend its home, as the honeybee does. The sting of a leafcutting bee is about half as painful as honeybees and they do not leave a stinger behind. Unlike honeybees, leafcutting bees do not die after stinging.

No protective clothing is needed when working with leafcutting bees and the shelters do not pose any threat to the public, even when placed near homes. These bees are particularly fond of sweet clover and will visit it to the exclusion of alfalfa. Other crops visited for pollen are forage legumes, mints, crucifers and many weeds or garden plants. The adults commonly are found flying about near outbuildings, fence posts, cliff banks, or other suitable nesting sites. These leafcutter bees can utilize almost any small holes and will commonly plug small tubing, electrical sockets, and nail holes. Other favorite nesting sites are between the siding on frame homes and between or under the shakes or shingles on buildings. With such numerous nesting sites available, it is easy to understand why these bees became quite common and how large populations can be obtained for agricultural use.

Leafcutting Bees

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Economic Impact
Idaho is the number one producer of winter hardy varieties of alfalfa seed in the world and the alfalfa leafcutting bee is one the major reasons for this. As I drive about the valley this first week of July, I see the familiar sites of the leafcutter bee shelters throughout the area.  Inside are thousands of leafcutting bees going about their business of pollinating the alfalfa seed plants in bloom. In a month the bees will be through flying and harvest will begin the end of August. In less than those two and a half months these little bees will produce up to 1500 pounds of seed per acre making alfalfa seed one of the higher cash crops in the valley.

The ability of leafcutting bees to so rapidly pollinate a seed crop took me to Australia for 10 years from 1995-2006. During that time I helped write the protocols that would safely allow for the introduction of these bees into Australia. The ability to very rapidly pollinate an alfalfa (Lucerne as it is called in Australia) seed crop was considered a water conservation matter as it had the potential  to reduce the pollinating period in Australia by 6-8 weeks allowing for less water usage and reduced pesticide applications. There is still a going small population of those original bees there, but the ability to reproduce a sustainable population has proven to be difficult. So as you are driving throughout agricultural fields of the Treasure Valley and see the fields of blooming alfalfa spotted with nesting shelters for the leafcutting bees,  think about the contribution this small little bee has made to our area and state. I have often thought that the alfalfa leafcutting bee would be a good candidate as the State of Idaho’s official insect.

For more details on the alfalfa leafcutting bee, see: www.pollination.com Text of “Current Status of the Alfalfa Leafcutting Bee”

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