254 UNITED STATES NATIONAL MUSEUM BULLETIN 2 76 



times occur). This does not mean that all of the listed instars were 

 found in a single colony; it merely indicates which instars were found 

 in the one or more colonies that were examined. This information 

 should make it possible for anyone interested in studying Malacosoma 

 to estimate the dates that larvae could be found in a given area (keeping 

 in mind the fact that the date of hatching may vary as much as a month 

 from one year to another, depending on local weather conditions). It 

 may also be of value in planning the timing of other studies which 

 have to be carried out at a certain stage in seasonal advance, since the 

 hatching of tent caterpillars is closely correlated with other phenological 

 events such as the appearance of the first leaves of their host plants. 

 (See the section on life cycle, page 13.) 



The first host listed is the one on which the egg mass and/or speci- 

 mens which were reared were found, or the one most commonly at- 

 tacked in collections where they were not reared. Additional hosts are 

 those on which colonies or egg masses were found in the same vicinity. 

 Those marked with an asterisk (*) are hosts on which colonies or egg 

 masses were found, but which are not considered to be normal hosts 

 for oviposition. 



The scientific names of host plants are those used in Abrams and 

 Ferris (1940-1960), "Illustrated Flora of the Pacific States," with the 

 exception of chokecherry, for which Prunus virginiana has been used 

 throughout. Scientific names of species not found in the Pacific states 

 have been taken from the following floras which are listed in descending 

 order of use: Kearney and Peebles (1951), "Arizona Flora"; Shinners 

 (1958), "Spring Flora of the Dallas-Fort Worth area, Texas"; Moss 

 (1959), "Flora of Alberta"; and Harrington (1954), "Manual of the 

 Plants of Colorado." 



Elevations are usually accurate within + or — 100 feet. Those given 

 more precisely than 100-foot intervals were either taken from maps or 

 estimated from known elevations nearby. 



The collection data are arranged in the following order: 



Page 



M. disstria 255 



M, constridum constrictum 255 



M. constrictum austrinum 257 



M. tigris 257 



M. americanum 257 



M. californicum 259 



M. californicum californicum 270 



M. californicum ambisimile 271 



Intermediate populations — M. californicum californicum 



— M. californicum ambisimile . . . 272 



