The successional dynamics of arthropod diversity in 18 abandoned agricultur
al fields (age 15-54 yr) at Cedar Creek, MN, USA were determined using swee
p net sampling (44833 individuals of 618 species). Total arthropod species
richness and equitability (J), but not abundance, increased significantly w
ith field successional age. Herbivore and parasite species richness, but no
t detritivore and predator species richness, also increased significantly w
ith field age. All of these arthropod variables were significantly positive
ly correlated with plant species richness in the fields. When plant species
richness was included as a covariate in regressions, there were no longer
any significant effects of field age. These results supported the hypothesi
s that increases in arthropod diversity with field age are influenced by in
creases in plant diversity. The additional significant positive dependence
of herbivore species richness on predator species richness suggests that pr
edator-prey interactions may also influence the successional dynamics of ar
thropod diversity. Nine of the ten most common arthropod species decreased
in abundance with field age, two of them significantly. The abundances of t
hese two generalist forb-feeding species, Melanoplus femurrubrum (Orthopter
a: Acrididae) and Scaphytopius acutus (Homoptera: Cicadellidae), each depen
ded significantly on amount of forbs. The average body size of arthropod sp
ecies (total and herbivores) decreased significantly with field age. An eff
iciency vs specialization hypothesis predicts such a decrease. Because plan
ts in later secondary succession are generally less palatable, a diversity
of smaller, potentially more specialized herbivores may have an advantage o
ver larger and more efficient herbivores in later succession.