56 MASS. EXPERIMENT STATION BULLETIN 339 



The losses could be somewhat reduced in the cases of derris and nicotine 

 tannate because many of the infested ears were marketed. The disposition of 

 such material was, however, not accurately recorded by the growers. 



The cost of materials for the season's program on both farms is shown in 

 the following table: 



Cost of Materials 



Number of Amount of 

 Applications each material Derris Nicotine Tannate 



Farm A 4 67m gals. $1.40 $1.24 



FarmB 5 92m gals. 1.92 1.69 



No figures were available for phenothiazine because the material is still in 

 the experimental stage and no market price was quoted. 



The prices of labor on the two farms varied greatly. The labor charges can 

 however, be determined for any individual locality from the estimates of the 

 Federal Entomologists in the Corn Borer Investigation. On the basis of these 

 estimates and our experience in one season, the time required per acre for the 

 first two sprays would average one-half day for one man, and due to the rapid 

 growth of the plants would average a full man-day per acre for subsequent 

 applications. 



Insects Concerned in the Dispersal of Dutch Elm Disease. (W. B. 



Becker.) Further research on the biology of the native elm bark beetle. 

 Hylurgopinus rufipes, is in progress. Life history studies indicate that there is 

 one complete generation a year and a partial second. Under some conditions, 

 larvae of the first generation will overwinter and transform to adults the 

 following spring. Due to differences in the rates of development, there is an 

 overlapping of generations. Both adults and larvae have been found over- 

 wintering in Amherst. Partially completed work on the development of the 

 immature stages within the bark points to a variation in the number of instars. 

 Soon after the adults emerged from trap logs in August many were seen digging 

 tunnels into the bark of near-by thrifty-appearing elms. These tunnels are of 

 the same type as those dug in the fall, in which to spend the winter, and are 

 similar to the feeding tunnels of Scolytus multistriatus, except that H. rufipes 

 tunnels have only been found in the bark on the trunks and larger limbs of 

 elms in the field whereas S. multistriatus prefer the smaller twigs and buds for 

 feeding tunnels and wounds, according to literature and observations by the 

 author. 



Spathius canadensis, a Braconid, was found to parasitize a small percentage 

 of the H. rufipes larvae. Numerous mites and several species of insects, of 

 which Collembola were the most abundant, were also found in the brood 

 galleries of H. rufipes. 



Because H. rufipes has been reported taken from several species of trees, 

 freshly cut logs of six species were used in the field and in individual cages as 

 traps for the adults of the first generation which emerged from American elms 

 in August. American elm, slippery elm, red maple, basswood, ash, and red 

 cedar were used. Egg galleries were constructed only in American elm. Nu- 

 merous holes were dug into the bark of slippery elm, and in some of these there 

 was a live adult. However no egg galleries were constructed. The red cedar 

 and red maple were untouched. Feeding on the basswood was negligible, while 

 the attack of a regular ash bark beetle spoiled the ash log experiment. 



Some preliminary experiments were being carried on with subcortical elm 

 bark temperature. The subcortical temperature of elm logs in the sun rose to 

 122° F. in the experiments recorded. 



