The relationship between population density and the size of host plant
patches was investigated for the red milkweed beetle Tetraopes tetrao
phthalmus inhabiting unmanipulated patches of Asclepias syriaca. The r
esource concentration hypothesis proposes that density-area patterns,
specifically that of increasing herbivore density with patch size, are
primarily a function of movement between host plant patches. This res
earch investigated the degree to which movement accounted for density-
area patterns. Poisson regression analysis of beetle abundance versus
milkweed patch size revealed that beetle density tended to increase wi
th patch size. The pattern of density and patch size resulted from loc
al reproduction and residence time. The density of emerging beetles te
nded to increase with patch size while emigration rates were unrelated
to patch size. Immigration rates were constant with patch size for ma
le beetles, and decreased with patch size for female beetles. Net flux
of beetles (immigration - emigration) did not vary with patch size fo
r male beetles and decreased with patch size for female beetles. Compa
risons are made between this system and previously studied systems whe
re movement plays a significant role in forming density area patterns.
Additionally, several hypotheses are presented which may account for
greater in situ recruitment and residence time in large patches.