1. CALLAHAM, R. Z. 1952. The role of quantitative oleoresin production in the susceptibility of pines to bark beetles. U.S. Bur. Ent. and Plant Quar., Forest Insect Lab., Berkeley, Calif., 8 pp. (Report on file at Pac. SW Forest and Range Expt. Sta., U.S. Forest Serv., Berkeley, Calif.)
2. CALLAHAM, R. Z. 1952a. Host selection and host susceptibility in western pine beetle-ponderosa pine complex. U.S. Bur. Ent. and Plant. Quar., Forest Insect Lab., Berkeley, Calif., 8 pp. (Report on file at Pac. SW Forest and Range Expt. Sta., U.S. Forest Serv., Berkeley, Calif.)
3. CALLAHAM, R. Z. 1953. Studies of the resistance of pines to bark-beetle attacks, season 1952. U.S. Bur. Ent. and Plant Quar., Forest Insect Lab., Berkeley, Calif., 27 pp., illus. (Report on file at Pac. SW Forest and Range Expt. Sta., U.S. Forest Serv., Berkeley, Calif.)
4. CALLAHAM, R. Z. 1953a. Host specificity in the Dendroctonus-Pinus complex. U.S. Bur. Ent. and Plant Quar., Forest Insect Lab., Berkeley, Calif., 12 pp., illus. (Special report BX-11 on file at Pac. SW Forest and Range Expt. Sta., U.S. Forest Serv., Berkeley, Calif.)
5. CALLAHAM, R. Z. 1955. Oleoresin production in the resistance of ponderosa pine to bark beetles. 120 pp., illus. (Doctor's thesis on file at Univ. of Calif., Berkeley).