146 
Psyche 
[Vol. 94 
Fig. 7. A competitive encounter in which one male has been lifted from the leaf 
surface by another male which has gotten a hold on his elytra. 
period and is often less than complete. Guarding females are effi- 
cient at repelling ants and wasps, but egg parasitoids, larval parasi- 
toids such as chalcid wasps and tachinid flies, pentatomid bugs and 
an entomophagous moth were able to gain access to guarded off- 
spring. These opportunities arose as groups moved between feeding 
sites or as individuals temporarily became separated from the rest of 
the group guarded by the mother. 
Maternal care in this species seems to have a clear and unambigu- 
ous selective value: as in many other subsocial insects, it lowers 
mortality due to predation (Tallamy and Wood 1986). Why, then, 
has subsociality evolved in A. sparsa but not in many other cassids 
some of whom share the same host plant? It may be significant that 
of the six species of Cassidinae on M. umbellata, only larvae of A. 
sparsa heavily exploit the terminal foliage. The other 5 species can 
be found anywhere on the plant, but their larvae tend to occur low 
