432 Retort of the Department of Entomology of the 



Table V. — Activities of Hibernating Brood or Pear Pstlla and Conditions 

 of Trees During the Spring of 1911. 



Date. 



Mar. 26 

 27 

 28 

 29 



April 



May 



30 



31 



1 



2 



3 



4 



5 



6 



7 



8 



9 



10 



11 



12 



13 



14 



15 



16 



17 



18 



19 



20 



21 



22 



23 



24 



25 



26 



27 



28 



29 



30 



1 



2 



3 



4 



5 



6 



7 



8 



9 



Activities of insects. 



Flies " appearing. 



Flies " return to 

 bark 



" Flies " reappear. 



Eggs being laid . 



Most eggs . 



Few nymphs. 



Last " flies ". . . 

 Many nymphs. 



Condition of trees. 



Cluster buds break- 

 ing 



Leaf buds open. 



Blossom buds opening 



Daily 

 mean 

 tem- 

 perature. 



°F. 

 52 

 45 

 28 



29 

 29 

 27 

 23 

 24 

 28 

 34 

 47 

 50 

 36 

 35 

 36 

 38 

 45 

 47 

 53 

 46 



38 

 32 

 34 

 43 

 52 

 47 

 45 

 38 

 42 

 38 

 40 

 56 

 60 

 64 

 63 

 61 

 54 

 36 

 35 

 40 

 44 

 49 

 55 

 61 

 56 



Weather. 



Cloudy. 

 Cloudy . 

 Cloudy . 



Cloudy 



Cloudy 



Partly cloudy . 

 Partly cloudy . 

 Partly cloudy . 



Clear 



Cloudy 



Cloudy 



Cloudy 



Partly cloudy . 

 Partly cloudy . 



Clear 



Clea 



Clear . . 

 Cloudv . 

 Cloudy. 

 Cloudy. 



Partly cloudy . 



Cloudy 



Cloudy 



Partly cloudy . 



Cloudy 



Clear 



Cloudy 



Cloudy 



Partly cloudy . 



Clear 



Clear 



Clear 



Partly cloudy . 

 Partly cloudy . 



Cloudy 



Cloudy 



Cloudy 



Cloudy 



Cloudy 



Clear 



Clear 



Clear 



Clear 



Clear 



Partly cloudy. 



Rain or 

 snow. 



.21 

 .34 



. 20 snow 



.03 snow 

 .29 snow 



. 02 snow 

 Trace snow 



.10 

 .06 

 .21 



Trace 

 .05 



Trace 



.11 



Trace 

 .33 



Trace 

 Trace 



.52 

 .01 

 .01 

 .03 



.03 



.17 



.52 

 Trace 

 Trace 



.04 



of the rough bark. On April 6, 1911, at a mean temperature of 

 50° F. the " flies " reappeared and did not again seek shelter although 

 on the following day the cold was severe. 



A knowledge of the time at which migrations of considerable 

 numbers of the insects may be expected in the spring through a 

 series of years is important since it may serve as a guide to control 

 measures at that period against this stage of the insect. In pub- 

 lished accounts of the life history of the pear psylla these activities 



