This paper reports on studies of biology and life history of the Zimmerman pine moth, Dioryctria zimmermani (Grote), in southern Michigan.
Adults emerged during the last 3 weeks of August and eggs hatched through mid-September. Eggs were laid almost entirely on the main stem and, upon hatching, the larvae entered recesses in the bark and spun hibernacula, ostensibly without feeding.
Studies on the vertical distribution of larvae and pupae showed a fairly uniform distribution over the main stem in spring and early summer. In late summer, a larger percentage was found in middle whorls.
Based on head capsule measurements, it is tentatively proposed that there are six larval stadia. Occurrence of parasitism in the last larval stadia is discussed, and a new egg parasite is reported.
The presence of D. abietivorella Grote in the study areas is noted, and discussed briefly.