1987] 
Windsor — Tortoise beetle, Acromis sparsa 
147 
on shade leaves. One hypothesis is that predators are more numer- 
ous on apical foliage and maternal care is more effective defense 
under these circumstances than the defensive attributes of solitary 
species (eg. egg and larval crypticity, spines, fecal shields, etc.). Api- 
cal foliage may harbor higher numbers of predators because it is 
more open, more easily searched by polybiine wasps and other fly- 
ing predators, and is nearer the active nectaries of other plants 
which concentrate such visitors (Hespenheide 1985). 
While the possibilities of larval survival may decrease toward the 
apex of the plant, nutritional rewards could increase. There is a 
growing body of evidence that insects feeding on young foliage grow 
more quickly and achieve larger pupal weights and adult size 
(Schroeder 1986, Damman 1986 and references therein). Larval 
developmental time should have a direct bearing on the number of 
groups of offspring a female can guard in a season. 
Most Cassidinae are sexually monomorphic or are very nearly so. 
Eberhard (1980) concluded after reviewing numerous examples that 
most beetles use their horns to physically displace their conspecific, 
sexual rivals at the location of important resources. The sexual 
dimorphism in A. sparsa, laterally elongated pronotum and elytra in 
large males, has probably evolved as a result of similar selection 
pressures. The chasing, flipping and immobilization of rivals which 
I observed suggest the existence of strong intrasexual competition 
although any size related advantages of these morphologies in A. 
sparsa have yet to be demonstrated. 
Why does strong competition between males exist in A. sparsa 
and not in many other Cassidinae? Females spend much of their 
time guarding offspring to the near exclusion of other activities. 
Although females with brood were occasionally courted by males, 
most did not attract nearby males. A large proportion of the female 
population leaves the mating pool during the time offspring are 
being guarded. Males, on the other hand, do not guard and are 
presumably sexually competent the entire time. As females begin to 
look for oviposition sites, which in themselves may be limiting, the 
operational sex ratio should be heavily biased in favor of males. 
While females become a rare item for males during brooding, 
their eventual reappearance should at least be fairly predictable: 
they nearly all go to the second or third open leaf on vine tips to 
oviposit. Larger males capitalize on this predictability by holding 
these sites and awaiting the arrival of females. Smaller males appear 
