Interesting this is an excerpt but the full article link is below
"Dennis and Kemp built a mathematical model of the growth of adult worker numbers in a beehive. The presence of more adult workers reduced the deaths of adult workers. Likewise, having more adult workers improved “rearing effectiveness,” or how well eggs, larvae and pupae are nurtured and raised to adulthood.
The critical hive size increases in response to any environmental factors that reduce rearing effectiveness or increase deaths of bees in the hive. In the presence of such an environmental factor, a beehive could find itself below the new, larger critical hive size. Loss of viability and hive failure would result."