34 MASS. EXPERIMENT STATION BULLETIN 305 



appear more promising than any of the native species. The work was carried 

 on in cooperation with the U. S. Bureau of Entcmolog}- and the liberations were 

 made under the direction of the ^'arious county agents. 



Twig collections previous to liberation indicated that the parasites were not 

 present naturally in these counties. Similar collections made in late summer 

 from the orchards where colonies of Macrocentriis were liberated showed that 

 in every case the parasites had beccme well established. Further studies will be 

 necessary to determine whether the insect can successfully winter over in all 

 sections of the State. Recovery records from orchards in Hampden County, 

 where liberations had been made in previous \ears, showed from 43 to 88 per cent 

 of parasitism. 



Plum Curculio. (W. D. Whitcomb, Waltham.) Continuing previous ex- 

 periments to determine the effect of temperature on the activity of the plum 

 curculio, 140 pairs of adult curculios were divided into 4 groups of 35 each. 

 The groups were confined for periods of 10 and 20 days at 55°, 65°, 75°, and 85° P., 

 after which they were transferred to the other temperatures in the series for a 

 similar length of time. Daily records were kept of the activitv of the beetles, as 

 indicated by the number of feeding punctures per beetle and the number of eggs 

 laid by each female. These experiments clearh- verified the results of previous 

 work which had shown a consistent increase in both feeding and oviposition with 

 each increase in temperature. 



In general the average activity of the beetles when placed in a certain tempera- 

 ture at any time regardless of the previous environment was consistent with the 

 average activity during a continued exposure to that temperature. An exposure 

 to a higher temperature increased activity, and to a lower temperature decreased 

 activity with one exception. This exception was recorded when a 20-day ex- 

 posure at 85° F. shewed slightly less activity than a prev'ous 10-day exposure 

 at 75°. Other observations as well as this exception indicated that there is a 

 tendency toward decreased activity at temperatures above 75°. 



The average number of feeding punctures per beetle per day during 10 da\s 

 at 65° F. was 3.02, while this activity during a similar exposure after a 20-day 

 confinement at 55° was 3.54, indicating that a low temperature not onl\- retards 

 activity but also produces a supply of stored energy which results in a slight 

 supernormal activity when the temperature is increased. It also appeared that a 

 similar reaction in the opposite direction took place, when it was observed that 

 the average number of punctures at 55°, 65°, or 75° was less after a previous 

 exposure of 10 or 20 da\s at 85° than at a constant exposure to those temperatures. 

 Oviposition records were similar but showed more variation. 



Laboratory tests of several stomach poisons which might be more desirable 

 to use than lead arsenate for combating the adult plum curculio indicated that 

 both calcium arsenate and manganese arsenate were slightly more toxic than 

 lead arsenate, and that barium fluosilicate and sodium aluminum fluoride were 

 only slightly less effective and promising. Nicotine tannate, a sulfur — carbon 

 disulfide emulsion, and a zinc sulfate — lime — derris mixture were failures in 

 this test. 



Biology and Control of the Apple Leaf-Curling Midge. (\\ . I). Whitccmb, 

 Waltham.) The apple leaf-curling midge, tentatively determined as Dasynetira 

 niali Kieffer, which has apparently been introduced from F^urope. is now estab- 

 lished in northeastern Massachusetts and southeastern New Hampshire. It 

 was first observed in this counlr\- in 1928 but previous to 1933 was not known to 

 be present outside of the town of Ipswich. Recent reports, however, indicate 



