20 UNITED STATES NATIONAL MUSEUM BULLETIN 276 



become so desiccated and shrivelled that they are usually only % to 

 % of an inch long at death. Complete desiccation and death usually 

 occur at a temperature of about 30° C. in from 3 to 5 days after the 

 first symptoms are noticed. 



Parasites 



All indications in the literature (Langston, 1957, etc.) are that the 

 parasites of Malacosoma are not host specific and consequently could 

 not be expected to provide any information which would be of sys- 

 tematic value. All c^g and larval parasites reared during this study 

 were saved and are listed in Appendix IV (page 291). 



Egg Masses 



After mating, females immediately begin searching for a suitable 

 oviposition site, and under caged conditions they often crawl around 

 with wings vibrating for some time before selecting a spot. Each female 

 normally deposits her eggs as a single mass on a suitable host plant 

 and in a way that may be characteristic for the species. The number of 

 eggs per mass varies considerably, ranging from less than 100 to more 

 than 400, and as many as 600, but most often ranging from 1 50 to 250. 

 Virgin females may lay a few eggs, but these are always infertile and 

 laid in a highly irregular way. 



All North American species except M. tigris cover the eggs with a 

 frothy material secreted by the accessory glands and termed spumaline 

 by Hodson and Weinman (1945). Bubbles of spumaline are released 

 just before each egg is placed in position. The egg is placed with the 

 long axis perpendicular to the stem and with the micropyle toward 

 the outside. 



The spumaline varies considerably in color, texture, and toughness 

 from species to species, and in the case of M. californicum and M. in- 

 curvum from population to population. The color ranges from nearly 

 pure white in some populations to a very dark brown in others. Rarely 

 the spumaline on different egg masses of the same local population may 

 be different colors. Immediately after the eggs are laid, the spumaline is 

 lightest, but may become considerably darker with age. The toughness 

 of the spumaline depends to some extent on the humidity, being more 

 brittle when dryer. Resistance of the spumaline to weathering varies, 

 apparently because of individual differences in the females (Wellington, 

 1959). 



