230 MASS. EXPERIMENT STATION BULLETIN 180. 



larvae moved their mouth parts considerably. The weather was cool 

 during the entire period (July 29 and 30) in which this investigation was 

 in progress, the maximum temperature in the sun at the station bog 

 being 80° F. and the minimum bog temperature being 40°. 



Cocoons of parasitized fruit worms are usually much smaller and more 

 delicate than those of unparasitized ones. 



Submergence tests were conducted with fruit worms in their cocoons, 

 as follows: — 



1. Six small cheesecloth sacks, each containing 20 cocoons, were sub- 

 merged to a depth of 2 feet in a pond at 10.30 a.m., September 14. They 

 were all taken from the water and examined in the afternoon of September 

 26, and all the worms were found dead, a majority of them being partly 

 decomposed. Most of them had left their cocoons and were on the inside 

 of the sacks. 



2. Three lots of cocoons of 20 each were submerged in cheesecloth sacks 

 to a depth of 2 feet in a pond at 9 a.m., September 30. These were all taken 

 from the water and examined between 11 a.m. and 1 p.m., October 12. All 

 the worms were found dead, most of them being more or less decomposed. 

 About half had left their cocoons and were clinging to the inside of the 

 sacks. 



3. Two cheesecloth sacks, each containing 20 cocoons, were submerged 

 in 2 feet of water in a pond at 3 p.m., October 12. These sacks were taken 

 out and examined at 5 p.m., October 24. Most of the worms were found 

 dead and more or less decomposed, as in the previous tests, but 7 were 

 alive in one sack and 2 in the other. 



4. Two cheesecloth sacks, each containing 20 cocoons, were submerged 

 to a depth of 2 feet in a pond at 8 a.m., October 25. They were taken out 

 and examined on November 6, 17 being found alive in one sack and 8 in 

 the other. 



In all these tests the sacks were of the same material, were tied up and 

 submerged in the same way, to the same depth in the same place and for 

 practically the same length of time. It will be seen that as the season 

 advanced the submergence had much less effect on the worms. As the 

 pond grew colder fast while these tests were in progress their results sug- 

 gested that the temperature of the water largely determined its effect. 



At 1 p.m., Jan. 3, 1917, a weighted cheesecloth sack, containing 15 fruit 

 worms in their cocoons, was placed in the bottom of each of two 1-quart 

 cans full of water, the water being at a temperature of 59^° F., and the 

 cans, with their covers on tight, were placed in a chicken incubator to- 

 gether with Green maximum and minimum registering thermometers, the 

 incubator being set to run at a temperature of 60° F. As a check on these 

 cans, two similar cans containing similar lots of fruit worms were placed 

 in a pail of water at the same time, the temperature of the water in the 

 cans and in the pail around them being about 35° F. The pail, together 

 with maximum and minimum registering thermometers, was placed in a 

 barrel the temperature of the air in which was about 37° F. The barrel 

 was headed up and buried in hay to keep its contents at an even tempera- 



