Abstract
North American Ips of Group II (Hopping, 196îb) are I. emarginatus (Leconre) and I. knattsi Swaine. They are the only Ips having the third declivital spine emarginate ar the tip. They breed in various species of pine. The distribution of I. emarginatus is from southern British Columbia to California and eastward to Montana. I. knausi is found in Colorado, New Mexico and Arizona. A key to the species is given. I. plastographus (Leconte) is the sole representative of Group III. It is the only four-spined Ips with the sutures of the autennal club strongly angled at the middle. I. plastographus breeds in species of pine. It occurs from southern British Columbia southward in the western United States and through Mexico into Guatemala. Hosts and more detailed distributions are given for species in Groups IT and III.