i , <i Beis 














































tO pass freely through door facilitat 

és introducing and removing material. 
paratus costs about $10.00 including ron thermostat. A nearly constant hum- 
of 89% varying but two degrees has ined f one week and a minimum 
ity of about Shai degrees varying eé z | been maintained for 
v days. The results so far indicate that this apparatus, with slight alteration, 
be used to determine the effects of certain envir al 
tal yess which could 
| ermohygrograph intro- 
betes short periods of 
Stancy as to render any conclusions extremely difficult. The use of the mean 
perature and mean humidity over a given period of time, though undoubtedly de- 
ly Significant, certainly does not take into consideration the frequency of 
mic and hygric variations. That this frequency is as impertant as the mean or 
6 Maximum and minimum extremes has as much ground as any of the other theories | 
vanced upon this subject. The economic importance of such knowledge is inestime- 
E Through the past fifty years, field observations on the Hessian Fly have 
Mgnt no conclusive means of foretelling the time of fly emergence. The same 
x of results may be observed in almost any continued study of insects in the 
Field. Their time of appearance and time of activity vary from year to year. 
These variations are undoubtedly due to climatic conditions and until we can posi- 
tively Say what climatic conditions and what combinations of climatic conditions 
rill produce a given effect, we cannot BOpS to prognosticate insect outbreaks. 
The great expense attached to constructing all the apparatuses heretofore described 
ace such experimental work without the scope of the average field worker. So far 
have made but few tests. However, as these are so significant it may be of ine 
@St to review them here. 
Experiments were made with larvae of Agriotes mancus a common wireworm crop 
ee these larvae being used in each experiment except (A) in which ten larvae were 
a. These larvae were all from material ‘hat has been under observation at least 
| year and up to the time of the experiments had been exposed to almost identical 
; ironmental conditions. 
Experiment Temperature . Relative humidity Duration Eifect 
7 A . 71+86° submerged 30 days Not fatal 
I 80° 449, 8 hours do, 
as, 100° 56 22" | | Fatal 
Iv rave 24%, ie * do. 
VII ; 105° 89%, 5s do, 
ie 
o 4 
bq 



VIII 60-~80° shows 2. days Not fatal 
With but a a point in each limiting zone a most interesting chart can be 
Blatted. The relative arc of course is entirely id only be defined 
y repeated ex De ciact ation to place additional stermin on. Once detsr- 
a, each zone will probably assume the form o € e as suggested by Pierce. 
these curves take approzimately the general direction indicated is quite evident, 
pever, and it appears from these observations (which are only given to illustrate 
) application cf the data and not as positive statements relative to the material 
ted) that this insect has an scam sphere lying between 50% and 80% relative 
sity and between 55° and 75° temperature and a sphere of instant fatality 
fing without 10% relative Nr at temperatures below 60° F. and above 120° F 
Ath relative humidity above 24%. These conclusions, though so 2, tily drawn, are 
forne out by the cbservations of the past three seasons on material in our rearing 
wages. In the early summer we have a peri f high activity of Elateria larvas, 
od u 
icated by molting and pupating; as the temperature rises we have @ period of rela 
; inactivity followed by a lesser period of activity in the cooler days of sarly 
L, which is in turn es gengle by a very inactive period covering the cold weather. 
[Signed] J. A. Hyslop. 
