REVISION MALACOSOMA HTJBNER EST NORTH AMERICA 13 



In summary, it can be said that tent caterpillars are a nuisance 

 problem in most parts of North America, but they can cause economic 

 losses to forests, rangeland, and associated activities in areas where 

 high populations persist for several succeeding years. 



Life Cycle 



The life cycles of all species of Malacosoma are very similar. Snod- 

 grass (1938) gives a general description of M . americanum from c^g 

 through adult that is better and more detailed than others of a popular 

 nature. 



The eggs (usually 150-200, but ranging from a few^ to as many as 

 600) are laid as a mass encircling, or partially encircling, small twigs 

 of the host plant, or as a relatively flat mass on larger branches, or 

 even near the ground as a flat mass on the trunks of small trees or 

 shrubs. As the eggs are deposited they are held in place by a frothy 

 substance from the accessory glands which has been named "spumaline" 

 by Hodson and Weinman (1945). Most species also cover the eggs 

 with a layer of spumaline as they are laid. Embryological development 

 begins immediately and the young caterpillars are fully formed within 

 the eggs 2 to 3 weeks later. They then enter a period of diapause for a 

 few months, followed by dormancy which lasts until the next spring. 



Hatching takes place about the time the first new leaves appear in 

 spring. This may range anywhere from late January in Florida to 

 June at high elevations in the western mountains. The caterpillars' 

 first meal necessarily consists of chorion and spumaline, since they 

 must chew their way out, but they soon begin attacking buds or leaves 

 and constructing their tent on a branch or in a nearby crotch if they 

 happen to be a tentbuilding species. They do not feed within their 

 tents; instead they crawl out to neighboring branches, spinning a 

 strand of silk wherever they go and usually following it back to their 

 tent after feeding. Those species which do not build tents cluster on 

 branches or trunks between feeding periods. Tent caterpillars feed 

 on a wide variety of hosts, but most commonly they are found on 

 species belonging to the families Rosaceae, Fagaceae, and Salicaceae. 



The number of instars is not constant, but the caterpillars usually pass 

 through five or six instars in from 4 to 8 weeks, depending on weather 

 conditions. Molting customarily takes place inside or on the tents 

 of those species that build tents, or on a mat of silk spun on branches 

 or trunks by the species that do not build tents. Most of the damage 

 is caused by the last two instars, which consume many times as much 



