REVISION MALACOSOMA HUBNER IN NORTH AMERICA 27 



A good example of the possible influence of the life form of the 

 host on the shape of the tent was found at the site of Coll. No. 25, 

 where M. calijornicum californicum was commonly found on Quercus 

 agrifolia and on Salix sp. Tents were more common on Q. agrijolia 

 than on Salix, but it seems reasonable to assume that all colonies 

 were members of the same local population, and it seems unlikely that 

 one host would have a greater number of active colonies than the other, 

 although the possibility cannot be completely ruled out. In general, 

 the tents near the tips of the branches on Q_. agrijolia were more com- 

 pact and equidimensional than were those near the tips of the branches 

 of the willows. The willows provided only relatively flexible leaves 

 for the support of tents near die tips of the branches, while the oaks 

 provided stiffer leaves and numerous twigs for support near the tips. 

 If the colonies on both hosts are assumed to be similar with respect 

 to the types of larvae of which they are composed, then it seems prob- 

 able that the life form of the host influenced the shape of the tent to 

 some extent. 



A similar, but not exactly identical situation is present in the Mojave 

 Desert area where M. calijornicum fragile occurs on Prunus fasciculata, 

 the desert almond. This shrub usually has many rather stiflT, inter- 

 locking branches and twigs which form innumerable sites that would 

 be suitable for tents. Many of the twigs are rather long and they may 

 extend beyond the main part of the shrub for several inches. Such 

 twigs appear to be suitable locations for the construction of elongate 

 tents, but they are rarely used, possibly because the leaves of the desert 

 almond are so small (about % of an inch long by % of an inch wide) 

 that there would be practically no space inside a tent which was con- 

 structed over such a slim framework. 



It is not known what types of larvae built the tents that were ob- 

 served, but many of the tents were more or less equidimensional and 

 were constructed over a framework of numerous intertwined twigs and 

 branches, making it impossible to remove them without cutting through 

 several twigs and branches. Other tents were built on individual 

 branches, but these tents usually were constructed where several twigs 

 left the main branch and were most often equidimensional (fig. 335). 

 In this case, as in the case of M. californicum californicum on Q. agrifolia, 

 it seems probable that the life form of the host may influence the shape 

 of the tent, but only additional study of colonies containing known 

 larval types will tell whether or not it does and to what extent. 



M. disstria, the forest tent caterpillar, is the only species of Malaco- 

 soma which builds no tent at all. The larvae normally rest on leaves, 

 branches, or trunks (fig. 332) when not feeding, moving to the shady 

 or sunny side, depending on the temperature. When they molt, they 



279-280—68 3 



