Of the three groups, the insect pathologist is perhaps the most interested in the last, but the other two have members that are also important from a pathological standpoint as well as from the standpoint of their role in biological control.

THE POSSIBILITY OF USING PATHOGENIC micro-organisms to control destructive pests has been envisioned for a long time. From time to time efforts to institute the control of certain insects by such measures have been made in various parts of the world, but the reports of the results have been inconsistent. In recent years there has appeared a need to reappraise the possibilities of this method in the light of new techniques and newer knowledge concerning the effect of disease on insect populations.

One of the most successful attempts to control a serious insect pest in the United States by means of an infectious agent has been the application of the bacterial milky diseases against the Japanese beetle. Once the bacterial spores are introduced into an infested area they are able to persist for long periods of time (being periodically revitalized by infecting invading grubs) ; hence the permanency of the method is one of its outstanding merits. In some areas, effective artificial control of other pests by means of fungi and viruses has also been attained. Dissemination of viruses by means of aircraft to combat certain field crop pests (e. g., the alfalfa caterpillar) has been accomplished and would apparently also be applicable against certain forest insects.

Besides the advantage of permanency in some instances, other advantages of the microbial method include the fact that successful microbial control can be a relatively inexpensive method of reducing populations of destructive insects. Large quantities of most micro-organisms may be produced in a relatively short time and easily distributed as sprays or dusts. Furthermore, microbial control is a "natural" method of control, and therefore may increase its effectiveness by natural means after once having been introduced into an area. Practically all entomogenous micro-organisms are harmless to animals and plants. The potential dangers of some chemical residues to the host plants or to the consumers of the plants ordinarily is not a factor in microbial control. Because most micro-organisms are not appreciably affected by many of the insecticides, the use of these two agencies at the same time is practicable.

In considering the over-all role of micro-organisms in the control of insects and in the suppression of insect populations, one should remember that regardless of man's activities along this line a tremendous toll of insect life is being taken ken continuously in nature through the pathogenic action of entomogenous micro-organisms. Instances in which nature institutes effective control of an insect species through the agency of disease are common and unceasing. If for no other reason, therefore, it behooves the entomologist and the agriculturist interested in the ecology of insects to be cognizant of those micro-organisms capable of causing disease among these animals and the effect of the diseases on insect populations and activity. Only by including knowledge of this group of enemies of arthropods along with the other more frequently recognized groups can we hope to gain a more complete understanding of insect life.

EDWARD A. STEINHAUS is an associate professor of insect pathology in the University of California, Berkeley, where he is in charge of the teaching and research program in insect pathology. He is author of the book, Principles of Insect Pathology, published by the McGraw-Hill Book Co. in 1949.

The Laboratory of Insect Pathology is a part of the division of biological control in the College of Agriculture at the University of California, and as such it was the first laboratory of its kind to be organized (in 1945) for the Purpose of conducting a full teaching and research program in all phases of the subject. The facilities of the laboratory are available to entomologists, farmers, and others interested in having insect specimens diagnosed as to their diseases.

Specimens (subject to quarantine regulations) submitted for diagnoses should be securely packaged, but should not be placed in alcohol or other preservative. They may be sent by fast mail directly to the Laboratory of Insect Pathology, Division of Biological Control, University of California, Berkeley 4, Calif.