A number of the new insecticides chlordane, toxaphene, lindane, heptachlor, dieldrin, and aldrin are effective as dusts against fleas.

Although the application of DDT to infested buildings and on animals has provided an effective insecticide for controlling fleas and flea-borne disease, the insecticide is of little immediate value in protecting individuals from attacks by the insects. Extensive studies have been conducted at Orlando to develop flea repellents for treatment of clothing for individual protection. Among the most effective of the materials tested are benzyl benzoate and undecylenic acid. The all-purpose tick repellent also is an effective treatment against fleas.

THE BED BUG does not transmit diseases, although it is one of the most widely distributed of the parasites that attack man. It is killed easily with many contact insecticides, but because of its habit of hiding in well-protected places it is difficult to eliminate from infested quarters with such treatments. The fumigation of quarters with hydrocyanic acid gas was used extensively, but it is almost impossible to reach all hiding places with sufficiently high concentrations of the gas to eliminate an infestation.

Because bed bugs were considered one of the more common and annoying pests in military installations, investigations of its control were made at Orlando.

The entomologists assigned to the project, A. W. Lindquist and A. H. Madden, decided that to be really effective an insecticide would have to kill the bed bugs on contact and remain indefinitely as a lethal residue. Therefore the idea of a residual-type treatment for controlling the insect was under investigation early in 1942, before DDT became available. They tested several hundred insecticides in the laboratory. Pyrethrum and a synergist, n-butyl undecylenamide, was the most effective treatment developed during the early months of their research. Special cages that had good hiding places were heavily infested with bugs from the laboratory colony. The surfaces were then treated with pyrethrum spray. Bed bugs were placed in the cage every week thereafter. The residual deposit of pyrethrum and synergist killed the bugs for 3 or 4 weeks. Unfortunately, though, all available supplies of the insecticide were required for controlling mosquitoes, lice, and other more important insects.

When DDT became available, it was tested immediately as a residual treatment. Bed bugs added to the test cages were killed week after week. Homes infested with the bugs were then treated by spraying the beds and walls of sleeping quarters. Each week the beds were examined, but no living bed bugs were found. As a further check, 25 bugs from the laboratory colony were placed on the beds each week by the following week, only dead bugs could be found.

Colonel J. Q. A. Daniels, medical officer of the Army air base at Orlando, was having difficulty controlling bed bugs in the barracks. Under his direction, a large-scale test was carried out. In April and May 1943 more than 100 barracks containing about 6,000 beds were thoroughly treated with DDT. Close checks on results were made for at least 6 months without finding any bed bugs. The tests not only demonstrated the value of DDT against the bed bug but were of even greater importance in establishing the potential value of the principle of residual treatment against more important insects, particularly mosquitoes and flies.

THE SCIENTISTS who have taken part in research on the control of the mosquitoes, lice, mites, fleas, ticks, bed bugs, and flies have vastly improved the health, welfare, and comfort of mankind. The methods they have developed for destroying these vectors of diseases, I believe, will make serious epidemics of typhus, malaria, and plague a thing of the past. But the job of teaching people how to profit by the advances is far from complete, even though organizations such as the World Health Organization are disseminating information about these significant developments.

E. F. KNIPLING, a graduate of Texas Agricultural and Mechanical College and Iowa State College, is in charge of the division of insects affecting man and animals of the Bureau of Entomology and Plant Quarantine. He has been with the Department of Agriculture since 1931. During the Second World War, Dr. Knipling was in charge of the laboratory at Orlando, Fla. The laboratory was awarded the Distinguished Service Award of the Department of Agriculture in 1947. The Army awarded Dr. Knipling the Medal for Merit and the United States Typhus Commission Medal, and the King of England awarded him the Medal for Services in the Cause of Freedom for the contributions he made at Orlando.

Squash bug.

Tomato hornworm.

Harlequin bug.