Mild winters and butterflies

[Michael Gochfeld]

There have been several good suggestions for studying the impact of a 
mild, snowless winter on butterfly emergence and population (or on 
almost any other taxa as well, for that matter).  It's not easy to 
predict what will happen to any given species.  A warm snowless winter 
(like ours has been in NJ) would differ from a very cold snowless winter 
, I presume since the insulating layer of snow would not be available to 
protect against the cold.  This winter, with hardly any nights below 15F 
and lots of days above 50F, that lack of insulation may not matter here. 
 
What's more likely to happen is that things (plants, insects, etc) may 
start developing and then get nailed by a late winter (March-April) 
blizzard.  

Another complication has to do with the spring temperatures.  Our last 
warm winter was followed by a protracted, cold, wet spring, so that 
emergences were delayed. 

It brings to mind my botany professors PhD research done in the 1920's. 
 He went around inserting thermocouples into buds of various trees, for 
several winters and concluded that for each species it was the 
cumulative temperature (the analogy of degree-days), above some 
threshold, that determined when buds began to open.  It is likely that 
similar mechanisms control insect emergences as well, but they'd require 
detailed study.   At least that's my three cents. 

Mike Gochfeld