The parasites of second- and third-instar Japanese beetles,Popillia japonicaNewman, and associated scarab larvae were identified in turf samples from 49 locations in Connecticut during the fall of 1986. Four of the seven species of scarab larvae encountered were introduced and accounted for 91% of the sample population. Recovered parasites included three species of protozoa, two bacteria, a rickettsia, and a fungus. The most common protozoa, cephaline eugregarines, were found in the gut of Japanese beetles from 42 locations, and in four other host species. A microsporidium,Ovavesicula popilliaeAndreadis and Hanula, was found in Japanese beetles from 34 sites. Overall, 25% of the larvae were infected, but prevalence was 80–90% in some locations. AnAdelinasp. infecting 19% of the Asiatic garden beetles,Maladera castanea(Arrow), was found at six locations and in two other scarab species. This is the first record ofAdelinasp. in these hosts. The bacteriaBacillus popilliaeDutky andB. lentimorbusDutky and a rickettsia,Rickettsiella popilliae(Dutky and Gooden) Philip, were also recovered from grubs.R. popilliaewas recovered from five species. Two of the infected species, the Asiatic garden beetle and the European chafer,Rhizotrogus majalis(Razoumowsky), are new records as natural hosts for this pathogen. The incidence ofB. popilliae(3.5%) was comparable with previous reports from Connecticut. The fungus,Metarhizium anisopliae(Metch.), infected 1.2% of the Japanese beetles.