In the course of routine field work I often carried a Schultheis quick-reading thermometer, and from time to time I had opportunities to take the body temperatures of blue racers newly captured by hand. The trend of these records indicated the temperature range within which the snakes normally limit their activity, and the preferred temperature. In an earlier publication (Fitch, 1956:459-460) based on a few more than half the number of records of temperature now available, I discussed responses of the blue racer to temperature. The newer data bear out the trends previously revealed; of 60 records, 39 are within the six-degree range from 29° to 35°, and records are most concentrated in the one-degree range, 34° to 35°. Racers were found active at air temperatures between 15.5° and 32.4°, with the greatest concentration between 26° and 27°. Compared with most other kinds of North American snakes, the racer is remarkably tolerant of heat, and often is several degrees warmer than the level that those of other genera will normally tolerate. Racers have been seen crawling in the sunshine, or basking on days that were uncomfortably hot for humans. For example, on August 28, a large female racer released from a trap was followed and her behavior observed; after crawling some 50 feet through the grass she climbed from a ditch bank onto sunflower stalks and elm saplings, and came to rest among the stalks, in a spot strategically situated for catching grasshoppers. More than half her body was exposed to sunshine and air temperature was slightly above 34° Centigrade, yet the snake showed no sign of discomfort, and for the several minutes that she was kept under observation, did not attempt to withdraw into the shade. [Illustration: Fig. 6. Bodily temperatures of blue racers captured by hand in their natural surroundings. The preferred level is approximately the same as indicated by Fig. 5 (between 29° and 36° Centigrade), but some of the racers caught were not fully active and had lower temperatures. Some bias results from the fact that those having the lowest temperatures were the least active and hence were most easily caught.] [Illustration: Fig. 7. Air temperatures recorded at captures of the racers whose records were used in Fig. 6. An active racer typically maintains, by basking, a bodily temperature several degrees warmer than the air.] [Illustration: Fig. 8. Bodily temperatures of blue racers found in live-traps at Harvey County Park. Opportunity to regulate temperature by behavior was limited in these snakes in traps, which tended to match ambient temperatures.]