The Ingenious Professor Riley

Ingenuity is another quality prized by one generation of researchers after another. The idea of using one insect to control another insect that is interfering with man's crops was talked about for many years, but the first person to do something about it was Prof. C. V. Riley, chief entomologist for the Department for many years.

His first successful introduction was a parasitic insect, an enemy of the imported cabbage worm, from Europe. His success in this venture led to the most famous of all insect introductions, the Australian ladybird, and started a new chapter in man's fight against insects. The experiment so successfully controlled the cottony cushion scale of citrus trees in California that it has become a lighthouse in entomological history.

The cottony cushion scale was known to exist in Australia, but was not a bad pest there. No one knew just why, but Riley reasoned that there must be an insect in Australia that was holding the scale in check. Acting on this theory, he sent Albert Koebele to Australia in the fall of 1888 to find this unknown insect benefactor.

Koebele himself was a remarkable observer—or the whole experiment might have failed. Entomologists in Australia had seen the ladybird beetle and had associated it with control of the scale, but they had no actual proof. After finding several of these beetles feeding upon eggs of the scale, Koebele became convinced that the ladybird beetle must be the one he had been sent to get.

Another of Riley's assistants, D. W. Coquillett, remained in California to take care of the insects sent back by Koebele. The first three shipments totaled 129 beetles alive on arrival. Within 6 months these had increased to about 11,000 and had been sent out to more than 200 citrus growers. Within a year after the first shipment arrived, "the scale insect was practically no longer a factor to be considered in the cultivation of oranges and lemons in California," according to Dr. L. O. Howard, Riley's chief assistant and his successor as chief entomologist in the Department.

Riley had the knack of overcoming obstacles. In planning to send a man to Australia he was confronted with two difficulties—lack of funds to pay for the trip and lack of authority for travel outside the United States. These circumstances would have discouraged most men—but not Riley. The State Department had just received an appropriation to send a representative to the Melbourne Exposition to be held in 1889. Riley arranged with the Honorable Frank McCoppin, head of the commission to the exposition, to send Koebele to Australia on funds appropriated for the exposition. McCoppin, a native of California, agreed to pay the travel expense of Koebele but insisted that Riley send along another of his assistants to prepare a comprehensive report on the fair. The salaries of both men were paid by the Department and their expenses by the exposition commission. In the words of Dr. Howard, "the story of Koebele's work has become a classic in applied entomology and horticulture."

Attention to detail is also traditional, even if the detail is the smallest spore on the smallest insect. Witness G. F. White's work. It has been known for many years that diseases hold certain species of insects in check when weather and other conditions are favorable. Because of this knowledge, entomologists have spent much time studying these diseases, in the hope of using them to man's advantage. Probably the most intensive work was on a disease of chinch bugs. But the work was given up with the conclusion that the disease was already present in most fields and needed only the right kind of weather to multiply. When weather conditions were unfavorable, spreading the disease did little good. This conclusion seemed to apply to insect diseases in general.

After many years of work on insect diseases, Dr. White began a study of diseases of Japanese beetle grubs in 1933. Within 2 years he was convinced that a bacterial disease known as "milky disease" was responsible for reducing the population of beetles in older infested areas and could be used in control work. He died in 1937, but others carried his work on to completion. Dr. White spent almost a lifetime studying diseases of insects and, although he had made a name for himself in connection with diseases of honeybees and certain destructive caterpillars, his last job—development of the milky disease—proved a fitting climax to his career.

The milky disease is caused by bacteria that attack the grubs, causing them to become milky white in appearance. Although the organism is fatal to the beetle, it is harmless to plants, domestic animals, and people. When an area becomes fairly heavily infested, the disease is "planted" on top of the ground in the form of a dust. Spores are used for this purpose and are obtained from the bodies of infected grubs. The grubs are ground up and mixed with talc and lime. The disease multiplies very rapidly if enough grubs are present in the soil. It has been used widely in public parks in Washington, D. C., and is one of the most effective control measures so far found for Japanese beetle grubs.