66 MASS. EXPERIMENT STATION BULLETIN 369 



an occasional live larva and young adult of this brood have been found in the 

 logs during the winter. 



In logs from trees felled by the hurricane of September 21, 1938, eggs were laid 

 early in June 1939. The adults began to emerge on July 29 and emergence was 

 still being observed on October 18, 1939. 



The Smaller European Elm Bark Beetle, Scolylus multistriatus Marsham. The 

 adults reared from eggs laid in elm logs in May 1938 started to emerge in early 

 August of the same season, but many larvae passed the winter in the logs and 

 emerged as adults in June 1939. It is possible that adults that emerged after 

 early August 1939 belonged to the same brood, but it seems likely that they 

 resulted from a later attack on the same logs. 



Logs cut in midsummer of 1938 were infested with 5. multistriatus which passed 

 the winter in the immature stages, the adults emerging during the 1939 season. 



In logs from trees felled by the hurricane, eggs were being laid in early June 

 1939. The adults began to emerge on July 20 and emergence was still being 

 observed on September 10, 1939. 



In addition to the biology studies at Waltham, scouting work was carried on in 

 western Massachusetts for S. multistriatus. All towns adjacent to those already 

 known to be infested were visited, but the only findings new to this office occurred 

 in two locations in the town of Sheffield where adult beetles were found. 



The Effects of Solar Heat on the Subcortical Development of the Native Elm 

 Bark Beetle, Hylurgopinus rufipes (Eich.), at Amherst. (W. B. Becker.) Since 

 it was noticed that Hylurgopinus rufipes apparently did not breed successfully 

 in the upper side of small logs of American elm, Ulmus americana L., which were 

 in direct sunlight, it was decided to try to get more definite data on this subject. 



Elm logs infested with H. rufipes, from trees felled during the hurricane of 

 September 21, 1938, were used in the experiment. On July 12 and August 5, 

 18, and 21, 1939, logs were cut into two equal sections; one section was placed in a 

 large open field where it could receive direct sunlight from sunrise until near 

 sunset, and the other was placed under a tree in the shade of the foliage. All 

 logs were laid directly on the ground, in a north-south direction, and the grass 

 around the logs in the sun was kept short to prevent any possible shading. The 

 logs were put out about 8:30 a. m. and were removed about the same time of 

 day, after different periods of exposure. The beetle mortality in the upper half of 

 the logs in the sun was recorded and checked with the development in the lower 

 half and in the shaded logs. 



In the upper half of those logs in the sun, 100 percent mortality occurred in all 

 except one log. This log had relatively thick bark {\i to ^fg i"ch thick) and 

 had been exposed for only 1 day (8:30 a. m. on August 18 to 8:30 a. m. on August 

 19). Even in this log, however, only 2 larvae, 1 pupa, and 2 adults were alive, 

 all of them being on the east side of the log only slightly above the line dividing 

 the upper half of the log from the lower half. This is where the sun first strikes 

 the logs in the morning when the temperature of the adjacent environment is 

 cooler than later in the day. 



In each case when logs were examined during the subcortical life of H. rufipes, 

 specimens were found alive in the under side of the logs in the sun and in any side 

 they happened to infest in the check logs in partial shade. Later such shaded 

 bark also showed the presence of emergence holes, which bore witness to the tact 

 that beetles had completed their development and depaited. 



In the upper half of the logs in the sun, the larvae killed in 12 or more days 

 beginning July 12 were severely desiccated, indicating that they were killed in 

 less time than that. The degree of desiccation appeared to vary more or less 

 with the length of exposure. 



