Common cattle grub adult.

It is also important that the area selected for grub control be as nearly square or circular as possible, rather than in the form of a long, narrow strip. In the latter case, flies from bordering pastures would be able to reach all farms in the area under control and quickly reinfest the grub-free cattle. Four or five townships are considered to be the optimum size for an initial project of moderate dimensions. Theoretically there is no limit in the size to which a program of this nature may grow.

Another factor to be considered is the existence of natural barriers against the return of the heel flies. The perfect place for a control project is an island. Heel flies apparently do not operate over large bodies of water, and grub-free cattle on an island a mile or more off the mainland apparently are not subject to natural reinfestation. In approximating such ideal circumstances, it is advisable to locate the area where natural barriers exist or to extend the area up to whatever barriers are at hand. Wide rivers and lakes discourage the activity of the heel fly. Mountains, forest, and even croplands from which cattle are absent are similarly effective. Less satisfactory are highways and railroad rights-of-way; the latter are not effective against the heel fly, but they may serve in many instances to define an area sharply.

Once the boundaries of the district have been established, all owners of dairy and beef cattle should be informed that loo-percent cooperation is desirable and that any untreated cattle within the area constitute a reservoir of infestation for the treated animals. Actually, if about 80 percent of the cattle can be included in the program the undertaking may be considered worth while. Participants in the project should be informed of the biology, pathology, economics, and therapeutics involved. A map should be prepared to show the boundaries, roads, and the location of farm and ranch units. A committee should be chosen to coordinate the activities.

The participant will find it useful to name an administrative head or group. If the program is a small one, the county agent or the local vocational agricultural instructor may serve in that capacity. If it is a large one, the duties may be assumed by a county cattlemen's association or a similar group.

Administrative duties will be many. Enough insecticide should be purchased for the treatment of all cattle within the project. Spray equipment must be provided for large herds. Some cattlemen's groups have found it expedient to purchase their own spraying equipment. Others have made use of county-owned machinery. Still others have contracted with commercial operators to conduct the work. The owners of small herds, who may want to treat their cattle by hand, must be provided with materials needed for the application of dusts and washes. When the time to apply treatment is determined, each neighborhood leader or committeeman should be prepared to see that work is coordinated on all farms and ranches within his district. Routes should be planned in advance for spraying crews, so that a minimum of time will be spent on each farm. Farmers who choose to apply insecticides by hand should be notified when treatment of their cattle is required. Groups of small operators might well pool facilities and labor. The work of the administrating or organizing body will be determined generally by the size of the project, the interest of the participants, the extent of cooperation, the kind of livestock management practiced, the nature of the terrain, and climate.

As WE STATED, the treatment of cattle every 30 or 40 days during the period when grubs are in their backs is essential if the grubs are to be destroyed. Two to four treatments a year therefore must be administered, depending on the section of the country. About three consecutive years of work may be required before one can appreciate the effectiveness of the program and its results in terms of sound hides, better beef, and more milk.

ERNEST W. LAAKE is research adviser in entomology, Office of Foreign Agricultural Relations. He has been stationed in Costa Rica and Ecuador.

IRWIN H. ROBERTS is a parasitologist in the zoological division of the Bureau of Animal Industry.

Introduced pine sawfly, male and female.

The poplar and willow borer, a weevil, whose cryptic coloration matches well the bark of its host trees.