More than half of our species of bees have a short season of activity. In most cases the timing of emergence of such bees with the first blooming of their natural host plants is remarkable. In the Sacramento Valley of California, where a nesting site of two species of Andrena was under observation, emergence of the bees and the first appearance of willow blossoms took place on the same day. Bad weather during the short period of activity of such bees is apt to be their most serious hazard.

The presence of permanent and suitable nesting sites may be as important as abundant forage for the maintenance of effective numbers of wild pollinators. The decline in populations of wild bees in agricultural areas has probably been brought about at least as much by destruction of nesting sites as by destruction of forage. In this connection it is interesting to speculate upon the probable history of populations of the alkali bee in central Utah. In view of the fact that common, introduced plants like alfalfa, sweet-clover, and Russian-thistle are almost the sole forage plants for these bees in the area, it appears that they must have actually increased following the appearance of white settlers. Many statements from the older farmers in the region attest to their abundance in the early days of alfalfa-seed growing. However, as cultivation increased, the nesting sites, although generally in poor soil, were plowed up and planted to alfalfa. Now only scattered areas are close enough to remaining nesting sites to be benefited. The best seed district in Utah from the standpoint of pollination by alkali bees is adjacent to many acres of permanent saltgrass pasture that furnishes plenty of suitable land for nesting.

Intensification of land utilization has played havoc with the nesting sites of wild bees. The old rail fences provided sites for many timber-inhabiting bees like leaf-cutting bees and Osmia and provided a network of areas of undisturbed ground for nesting and of wild plants for forage. The clean cultivation now practiced to destroy weeds and soil-inhabiting insects is wiping out many of these last sanctuaries. It may soon become necessary to determine in each area how valuable the wild bees are for the pollination of crops and whether nesting sites can be reserved for them in a manner compatible with good agriculture.

Destruction of harmful organisms together with conservation of beneficial ones should be our aim. Too often the ravages of the destructive forms are so conspicuous that we lose sight of the value of the beneficial forms. This is clearly evident in the use of insecticides. The necessity for. insecticidal control for many insect pests is unquestioned. But it is becoming increasingly apparent that the simple question, "Will this application provide economic control of the pest concerned?" must be expanded to, "Will this application fit into a general program calculated to control all important pests without presenting a hazard to health or seriously affecting beneficial parasites, predators, and pollinators?"

Conservation programs for wild bees have never been tried or even formulated on an area-wide basis. Although it is encouraging to know that a few seed growers are taking steps to protect known nesting sites, it is disheartening to know that most farmers do not appreciate the value of wild bees and are unlikely to take readily to conservation measures involving setting aside pieces of land and complicating the cropping procedures.

The following general measures should tend to conserve and even increase the numbers of many kinds of wild bees. Details for carrying them out would depend upon many local factors; local conditions would probably call for certain additional measures.

1. Apply insecticides to blossoming plants only when there is no other way to control the harmful insects. Such applications should be made between 7 p. m. and 7 a. m. and should contain only toxaphene, methoxychlor, or other toxicants demonstrated to be relatively safe for bees when used at the proper strength.

2. Provide a continuous supply of bloom throughout the season. Forage crops such as vetch, clover, and alfalfa make a good series lasting from late spring through summer. Fruit trees, maples, hawthorns, elderberries, and other hedgerow plants generally provide needed spring forage. Of course, each area would be best served by the plants suited to its own climate and agricultural needs.

3. Establish and maintain hedgerows around agricultural fields and along roadways, ditch banks, and canals. Pithy-stemmed plants such as elderberry, sumac, and tree-of-Heaven should be encouraged in such hedgerows. Light browsing would make them more suitable for nesting than if they were left undisturbed.

4. Hollow-stemmed plants such as milkthistle, wild parsnip, canebrake, and teasel should be broken over after the stalks are well developed. These will provide nesting places for leaf-cutting bees and harbor many hibernating species.

5. Establish and protect areas of bunch-type perennial grasses, especially along the tops of banks. They Will provide nesting places for bumble bees and tend to stabilize and shelter the banks. Banks so protected, especially if nearly vertical, are ideal nesting places for many kinds of bees.

6. Preserve known nesting sites of gregarious bees from being cultivated, flooded, trampled, or encroached upon by dense vegetation. Expand the available nesting ground if necessary, and establish new areas with the same conditions as populated sites. In the past few years many nesting sites of the alkali bee have been discovered by alfalfa-seed growers. Once apprised of their value, the growers have usually been willing and even anxious to keep them in an unaltered state. Several and perhaps most of the gregarious species of bees migrate in large groups to newly prepared areas. If other conditions for population increase are favorable, it should not take long for new areas to be populated.

Another approach to the problem is through better utilization of available populations of native pollinators. The following principles should apply to many crops.

1. Grow the crop in areas where native pollinators are known to be abundant. In most cases such areas will be adjacent to or surrounded by untilled land.

2. Limit the acreage of the crop in bloom at one time to that which the native pollinators can handle.

3. Reduce competitive sources of pollen and nectar.

4. Time the blooming of the crop with the period of greatest natural abundance of the pollinator. (In general, only forage crops would be concerned here.)

GEORGE E. BOHART, a member of the division of bee culture of the Bureau of Entomology and Plant Quarantine, is in charge of the pollination studies in connection with the production on of legume seed, conducted at the Legume Seed Research Laboratory in Logan, Utah.

The attention of the reader is directed to the section of color drawings in which appears a drawing of an alkali bee (Nomia sp.) tripping an alfalfa blossom and the nesting sites and life stages of the bees. Opposite the drawing is a description of the life history and pollination activities of alkali bees.