In 1933 he became chief of the Bureau of Entomology. The following year the merger he had worked for took place. Strong had brought the Bureau of Plant Quarantine, the insecticide division of the Bureau of Chemistry and Soils, the work on plant diseases conducted by the Bureau of Plant Industry, and the Bureau of Entomology into one unit, the Bureau of Entomology and Plant Quarantine. He kept strengthening the organization throughout his term of office.

Suddenly one night in 1941 Strong died. P. N. Armand, who had risen rapidly in the Bureau, became chief. Armand was a research man and under his direction during the Second World War a notable piece of research on insecticides took place the development of DDT at the Orlando, Fla., laboratory of the Bureau. Many other insecticides, insect repellents, and improved methods of applying them also were discovered or developed during the period. Dr. Armand died in 1950 after serving 9 years. Avery S. Hoyt succeeded him. The Bureau has 200 field laboratories and offices, each located in the midst of the insect problem with which it deals. Most of the laboratories are in rented quarters so they can move as the insects move. The work of the Bureau lies in three main fields, research, quarantine, and control. It has five regional offices and ten research divisions.

EXCITING EVENTS in entomology were taking place in other parts of the Government service.

Back in 1884 anybody who even suggested that an insect or tick could cause disease was looked upon as a queer person. Theobald Smith shared these views but in a few years he changed his mind.

The great Robert Koch in Germany was looking at the tiny microbes that carry disease. Smith wanted to look at microbes and he wanted to study under Koch. But Germany was a long way off for a man with no money. He had an M. D. degree but he was not interested in practicing medicine. He found just the job he wanted in the Bureau of Animal Industry. He went to work in a hot attic of a Federal building. His nights were his own, and in the long hours he absorbed everything Koch wrote about microbes.

Little did Smith know, as he poured over those books, that he was to solve the riddle of Texas fever. It was an odd disease. Southern stockmen bought healthy northern cattle, brought them to the South, and in a month the cattle got sick and died. Southern cattle came North, grazed with the northern cattle; in a month the fields were red with the blood of northern cattle. The southern cattle stayed healthy all the time regardless of the locality. The stockmen were in a panic. The Bureau of Animal Industry put Theobald Smith and F. L. Kilborne to work on the mystery.

Smith decided that he would move right out into the field with the disease. As he prepared for the summer work, Kilborne tossed out the idea that ticks might be causing Texas fever. Smith did not close his mind to this theory, especially when Kilborne told him that the cattlemen were saying, "No ticks no Texas fever."

In the summer heat of 1889 Kilborne set up open-air enclosures in fields to run the tests. In the first fenced-in field he put four tick-laden cows from North Carolina and six healthy cows from the North. Then just to see if ticks had anything to do with it, Kilborne picked by hand all the ticks off three other North Carolina cows, which he placed in the second field with four healthy northern cows. In a month all the northern cows in the first field were burning with fever, but those in the second field remained healthy.

Now another man by the name Cooper Curtice played an important but less glamorous part in the story of Texas fever. His job was to study the life cycle and habits of cattle fever ticks. Smith and Kilborne needed the facts he gathered to continue their experiments with ticks on cattle.

Smith looked at the blood of the dying cows and he spied some pear-shaped organisms. He examined the blood of many cows with Texas fever and every time he found the same pear-shaped objects. Could these be the germs of Texas fever? He was not sure. He looked at thousands of blood cells and made test after test with cattle and ticks in the fenced-in fields.

But he wanted more proof. He raised cattle ticks in his laboratory and in the summer of 1890 decided to put a number of the baby ticks on a cow in a box stall. Day after day he took blood from the cow. One day he found the cow hot with fever. He took a sample of her blood and found it thin and dark. He rushed to his microscope and there before him were the little pear-shaped organisms. His picture was complete. Texas fever had survived in these tiny baby ticks. Now he saw why there was a 30-day lapse before the northern cattle got the disease. It took just this length of time for the parent tick to drop off the animal, for the eggs to be laid, and for the young ticks to hatch, crawl up a cow's legs, and attach themselves to the body. The southern cattle became immune to the disease when they were calves.

For the first time in the history of man, a tick was proved to be a disease carrier. Theobald Smith's discovery started a chain of events in which certain ticks, insects, and mites were labeled disease carriers, and opened up a whole new field of entomology medical entomology.

The Bureau of Animal Industry made use of this discovery and with the help- of cooperating States wiped Texas fever out of the United States, except for a long, narrow strip next to the Rio Grande River in Texas. This is known as a buffer zone and will remain that way until Mexico eradicates the disease. The Bureau is making splendid headway in eradicating the destructive scab mites of livestock and is continuing the fight against other animal pests that cut our meat, milk, and wool supply.

ABOUT 10 YEARS after Theobald Smith's discovery, Walter Reed was called upon to fight a disease of humans. Yellow fever was raging in Cuba at the time the United States Army ordered Maj. Walter Reed to Quemado de Gilines. Cubans and American soldiers were dying every day. Reed had studied microbes but he could find none in the bodies of the victims.

The Commission, consisting of Jesse Lazear, James Carroll, Aristides Agrairionte, and Walter Reed, did not know what to do next. They had time on their hands, time enough to hear the voice of Carlos Finlay, ringing out, "Yellow fever is caused by a mosquito." Finlay was considered a fanatic in Cuba but the Commission had tried everything else and acknowledged that Finlay might be right. Anyway they talked to him and raised adult mosquitoes from the little black eggs he gave them.

Walter Reed decided to test the mosquito theory. First he needed guinea pigs; animals he had tested did not get yellow fever. He needed humans. His own commission accepted the challenge: One of the deadliest mosquitoes was put on the arm of James Carroll. A few days later Carroll had yellow fever and nearly died, but he was proud to be the first experimental victim of yellow fever.

Still another man got the disease from one of Lazear's laboratory-raised mosquitoes. Then Lazear himself must take the chance. But he did not use one of his own mosquitoes; he let a stray mosquito from the yellow fever ward in which he was working suck his blood. In 5 days he had a chill. In 6 days he was dead.