INSECT ENEMIES OF WESTERN FORESTS 



77 



The pupae are mottled, greenish brown, about one-half inch long, 

 and are unprotected by a cocoon. The moths appear within 10 to 14 

 days and during an epidemic are so abundant as to give the im- 

 pression of a snowstorm in the woods. Creeks, springs, and rivers 

 are covered with the dead bodies, and tree trunks are plastered wdth 

 them until heavy rains wash them into the ground or carry them 

 away. Thfere is one generation annually. 



Outbreaks usually last for about 3 years, after which they are 

 generally brought under control by the action of parasites, predators, 



and disease. Heavy 

 rains d u ring the 

 flight period, reduce 

 Qgg laying, checking 

 an epidemic and 

 hastening its decline. 

 Although nature 

 wdll ultimately bring 

 outbreaks under con- 

 trol, a vast amount 

 of timber might be, 

 saved if artificial 

 control measures 

 could be applied to 

 protect the trees 

 from heavy defolia- 

 tion. It has been 

 found that trees can 

 recover from a 50- 

 percent defoliation, 

 and in some cases a 

 75 - percent defolia- 

 tion is not fatal un- 

 less the trees are sub- 

 sequently attacked by 

 bark beetles. A t 

 present, airplane 

 dusting {SS, 6Jf) of- 

 fers the only prac- 

 tical means of controlling this defoliator on large forest areas, but 

 because of high risk and cost, it can be applied only under par- 

 ticularly favorable circumstances. (See discussion on p. 178.) 



The oak looper {Ellopia somniaria Hulst) (fig. 36) is so closely 

 related to the hemlock looper that some entomologists consider the 

 distinction questionable. At least this probably represents a variety 

 or race of loopers that shows a distinct preference for Oregon w^hite 

 (Garry's) oak, on which it feeds in Oregon and north w^ard into 

 British Columbia. Other trees may be attacked but usually only 

 when intermingled with the preferred host tree. In some seasons the 

 oaks in Willamette Valley in Oregon are completely defoliated over 

 large areas by this species. No permanent damage is done, how- 

 ever, since the oaks are able to leaf out again the following year. 









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- 



Figure o6. — The oak looper (Ellopia somniaria) : A, Cater 

 pillars on defoliated branch ; B. pupae ; C, adult moths, 

 female above, male below. Natural size. 



