Coccinellidae are predators on the soil surface of Diabrotica spp. and Cerotoma spp. larvae. Moreover, Coccinellidae may use substances produced by Chrysomelidae adults to locate them and to find other prey in the aerial part of plants and dispersal in crops, which is important for biological control. This work was done at the National Research Center of Corn and Sorghum (CNPMS) in Sete Lagoas, Minas Gerais State, Brazil. Crotalaria juncea (L.) (Fabaceae) was sown in a pesticide-free area and insects on the aerial parts were collected from six 200m² sample areas with an entomological net when the plants were 12 to 48-d-old. Adult specimens of Diabrotica speciosa (Germar, 1824), and Cerotoma arcuatus (Olivier, 1791) (Coleoptera: Chrysomelidae), Coleomegilla maculata (De Geer, 1775), and Cycloneda sanguinea (L., 1763) (Coleoptera: Coccinellidae), and unidentified larvae of Coccinellidae were collected. There were fewer C. arcuatus (5.93 ± 1.29 - total/number of sample areas) than D. speciosa (11.71 ± 1.29) and there were more adult C. sanguinea (1.43 ± 0.24) than C. maculata (0.36 ± 0.24). There were approximately four times as many adult Coccinellidae (1.71 ± 0.29) as larvae (0.43 ± 0.29), and there were fewer Chrysomelidae (88.8%) than Coccinellidae (11.2%). The numbers of insects from these families were similar on 9-17 and 19-30 January and 2-14 February. Chrysomelidae and Coccinellidae were found on C. juncea and, therefore, the chemical attraction of these insects could be used to advantage in pest management programs in this culture.
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