122 UNITED STATES NATIONAL MUSEUM BULLETIN 2 76 



In the areas where californicum fragile and californicum occurred 

 together with incurvum discolor atum, colonies of i. discoloratum were 

 never found on Prunus Jasciculata, and colonies of californicum fragile 

 and californicum were never found on Populus fremontii. Thus, to some 

 extent each is restricted to its preferred host, although both of them 

 may be found on hosts such as fruit trees which are not native to the 

 area. 



Observations made on californicum fragile at Kingman and Valentine, 

 Arizona, indicate that this host preference is quite strong for some 

 populations. At Kingman numerous colonies of c. fragile were found 

 on Prunus fasciculate just north of town, but not a single tent could 

 be located on several large cottonwoods growing a few hundred yards 

 closer to town. Many moths must be attracted to lights in Kingman, 

 and if they were attracted to streetlights near cottonwoods, they 

 would have ample opportunity to lay their eggs on them, but apparently 

 they do not do so. Near Valentine, the situation was even more con- 

 ducive to oviposition on cottonwoods since many c. fragile colonies 

 were found in Prunus fasciculata thickets which were growing beneath 

 the cottonwoods. Not a single tent could be located in any of the 

 cottonwoods. 



It seems unlikely that incurvum is merely a population of californicum 

 that has developed the described differences simply because it usually 

 lives on a different host (cottonwood), since the same differences were 

 found when both species were on fruit trees, which are not the native 

 host of either one. Nevertheless, it is desirable that each species be 

 reared on the other's preferred host, if possible, (maybe for several 

 generations) in order to determine what influence the host may have 

 on these differences, if any. 



In this regard, there is considerable work that can be done on 

 incurvum and its relationships to other populations of what are presently 

 regarded as californicum in this revision. These include nearby popula- 

 tions of californicum which lay &gg masses that do not have any specks, 

 and the populations of californicum which occur on aspen at higher 

 elevations. These populations are more fully discussed in the next 

 sections (pages 130, 134). 



It is possible that all of the populations of incurvum and californicum 

 could be linked together at various elevations to fonn a very complex 

 community that would not be adequately described by any formal 

 names we could apply to them. To demonstrate whether this is true 

 or not for any given area (and there are many areas), several seasons 

 of field study would be required, plus good fortune in avoiding the 

 numerous problems that may be encountered if I'earing and overwinter- 

 ing of egg masses is to be done. 



