Arthur M. Heimpel, 56, director of the insect pathology pioneering research laboratory for the Department of Agriculture and a leading entomologist, died Saturday at his Beltsville home after a heart attack.

Dr. Heimpel, who specialized in diseases of insects, was one of the developers of a major bacterial insect killer in the early 1970s. The bacillus, which was developed as an alternative to chemical insecticides such as DDT, was called bacillus thuringiensis and is the biggest selling biological insect killer on the market today.

Dr. Heimpel also served as a consultant to NASA in Houston, where he made safety tests on samples of lunar soil and rocks brought back from the moon.

He joined Agriculture in 1961 as head of the insect pathology laboratory and also served as national technical adviser in insect pathology. Before that, he was a researcher in insect pathology in his native Canada.

Dr. Heimpel was born in Baie d'Urfe Quebec. He earned master's and doctoral degrees in biology and entomology from Queen's University in Ontario and did postgraduate work at the University of California at Berkeley.

During World War II, he served in the Canadian Army in Europe.

He was a member of the World Health Organization advisory panel on insecticides and a founding member of the Society for Invertebrate Pathology, where he served as the first secretary-treasurer and later as president.

Dr. Heimpel was a part-time member of the graduate faculty in the Department of Entomology at the University of Maryland.

In 1966, he received the Agriculture Department's superior service award for his research.

Survivors include his wife, Elma Rae, of the home; five sons, Gordon M., of Berkeley Springs, W.Va., Bruce A. of Vienna, Austria, Michael A., of Olney, Donald E., of Laurel, and David L., of Beltsville, and a step-brother, Earl, of Canada.