Adapting to extremes of temperature is 

 another way for an insect to escape preda- 

 tion. In the deserts of the American South- 

 west, for example, the grasshopper Tri- 

 merotropis palladipennis tolerates body 

 temperatures near 122° F, so it can escape 

 to hot sand where lizards cannot venture. 

 Near Phoenix, the desert cicada is active in 

 the suinmer, singing on the hottest days at 

 noon, when birds are forced to retreat. 

 (The cicadas are able to do so because 

 their enlarged dermal glands "leak" water, 

 which evaporates and cools them; they re- 

 place the lost fluid by tapping into the 

 phloem of mesquite bushes.) Winter 

 moths operate on the same principle, but at 

 the other end of the temperature scale. 



Winter moths undoubtedly escape 



much predation by being active when po- 

 tential predators are either hibernating or 

 several thousands of miles away. But this 

 stratagem, like other defenses, is not with- 

 out its costs or problems. To pull it off, the 

 adult moths must find food in the dead of 

 winter, and the larvae must feed quickly 

 on early spring leaves and go into estiva- 

 tion before returning predators can eat 

 them. Perhaps the greatest challenge, how- 

 ever, is the cold itself. 



Most overwintering insects — whether 

 adult, larva, pupa, or egg — are laced with 

 antifreeze compounds, but investigations 

 by biologist John G. Duman, of Notre 

 Dame University, and me failed to detect 

 any antifreeze in winter moths. Their 

 blood freezes at 30° to 28° F, as does that 



of summer insects. Furthermore, they 

 don't "supercool" to temperatures very 

 much lower than those of summer-active 

 insects. (Had my freezer been much colder 

 than 32° F, the moths would have died 

 when they were frozen in the ice.) Why 

 they are not protected from freezing isn't 

 clear, but I suspect that the moths need to 

 retain their ability to become active at a 

 moment's notice on a warm winter day (by 

 "warm" day I mean one with evening tem- 

 peratures not lower than 32° F). Insects 

 "embalmed" with a concentrated solution 

 of alcohols may be protected from freez- 

 ing, but the chemicals infringe on an ac- 

 tive and coordinated life style. 



To maintain high temperatures in their 

 thorax, where the muscles for flight are lo- 



46 Natural History 2/94 



