12 BULLETix loso, u. s. departme:xt of agriculture. 
show that unless some change takes place, such as removing the 
debris or increasing it by brush from cutting, the proportion of 
those above and below the 5-foot line will remain approximately the 
same. Having determined TO per cent as being the average propor- 
tion of egg clusters laid above 5 feet, we can see just how valuable 
as a means of control nonhatch may be where the cold is sufficiently 
severe to kill all unprotected clusters. 
This particularly desirable state of affairs can not be looked for 
in a large part of the territor}^, for the temperature does not go 
low enough. The " point " notes show all variations between the 
above-mentioned percentage and no killing at all. Occasionally 
there is a mild winter with no low temperature and all eggs hatch 
the following spring. 
As nonhatch is caused by a temperature of from — 20° to —25° 
F. we can only expect to find it in territory subjected to such low 
degrees. Temperature records obtained from the 50 stations of 
the Weather Bureau which are located in the present area of in- 
festation show that any prophecy as to just what would happen 
in any locality would be quite useless. If the law of averages may 
be considered in this case, killing cold will occur in a majority of 
years in all of Maine and New Hampshire except a narrow area 
along the coast. In Massachusetts such cold, at least as reported by 
the weather stations, is the exception, but there appears to be a 
greater tendency toward it in Worcester County and the northern 
part of Middlesex County. The remainder of the infested area, 
with the exception of the northern part of Windham County in 
Connecticut from which extreme low temperatures are occasionally 
reported, apparently escapes cold severe enough to kill the eggs. 
These general conclusions, based as they are upon Weather Bureau 
records, apply to the sections as a whole. Local conditions, how- 
ever, vary to such an extent that we may find nonhatch in restricted 
areas in sections from which temperature records would apparently 
exclude it. " Observation point " investigations prove this to be 
particularly true of northern and central Massachusetts. 
It is possible that nonhatch is responsible for the slow increase of 
the gipsy moth in many localities where food conditions would seem 
to point to just the reverse. ' 
EFFECTS OF COLD ON PARASITES. 
There is reason to suppose that a drop in temperature low enough 
to kill the eggs will have some effect upon the imported parasites, 
particularly those which attack the eggs themselves. Two egg para- 
sites, namely, Anastatiis 'bifasciatus Fonsc. and Schedius kuvanae 
How., have become well established in New England. The former 
passes the winter as a full-grown larva within the egg of the host, 
^^o collections of eggs parasitized by Anastatiis lifasciatus have 
been made after extremely cold weather for the specific purpose 
of determining the effect of cold upon this parasite. It was noted, 
however, that there was a large percentage of dead parasites jn a 
bulk collection of eggs obtained after the cold winter of 1917-18. 
The locality from Avhich this collection came has been used for a 
number of vears as a source of material for new colonies, and eggs 
