Monitoring ground arthropods in maize and pasture fields of São Miguel and São Jorge Islands: IPM-Popillia Project

Study Extent

The study was conducted in a total of 20 fields, twelve fields sampled in São Miguel, six in maize fields, and six in pasture fields. For São Jorge, we sampled eight fields, four maize fields, and four pasture fields. A total of 18 pitfall traps were installed along three transects from the point closest to the crop entrance. The transects were 25 meters long, spaced 20 meters between them, and each transect contained six pitfalls traps spaced by 5 meters each. Pitfall traps were set from one of the stone walls or side of the fields into the center of the field to capture insects from the edges to the center of the field.

Sampling

Pitfall traps were used to sample the taxonomic and functional arthropod biodiversity by collecting predatory spiders, true bugs, ants, beetles, worms, and other epigean insects, on two agricultural habitats, maize and pasture fields of São Miguel and São Jorge Islands. Pitfall traps used consisted of standard 390 ml plastic cups, partially filled with propylene glycol, and deployed for seven consecutive days. Specimens collected were then transferred to ethanol (96%) and stored at -20 ºC. Paulo A.V. Borges and Mário Teixeira identified specimens based on the Azorean arthropods collection from “Portal da Biodiversidade dos Açores, University of the Azores” led by Professor Paulo A.V. Borges. The study was conducted in a total of 20 fields, twelve fields sampled in São Miguel, 6 in maize fields, and six in pasture fields. For São Jorge, we sampled eight fields, four maize fields, and four pasture fields. A total of 18 pitfall traps were deployed along three transects from the point closest to the crop entrance in each field. The transects were 25 meters long, spaced 20 meters between them, and each transect contained six pitfalls traps spaced by 5 meters each. Pitfall traps were set from one of the stone walls or side of the fields into the center of the field to capture insects from the edges to the center of the field. The aim of the study was to record ground arthropods as potential predators of P. japonica. Pitfall traps used consisted of standard 390 ml plastic cups, about 12 cm deep, 8 cm diameter at the top, and partially filled with propylene glycol. Traps were protected from predation, inundation with rainwater, and unwanted vertebrate capture (i.e., reptiles) using plastic plates sitting on wooden skewers 2 cm above the ground surface. As the traps are sometimes fragile, two cups could be used per trap, one placed inside the other. A total of 216 pitfall traps were installed on the 12 fields of São Miguel Island, 108 in maize fields and 108 in pasture fields. In São Jorge, a total of 144 pitfall traps were deployed, 72 in maize fields and 72 in pasture fields. After the seven days of sampling for São Miguel, the number of pitfalls successfully recovered was 195 pitfalls, 102 in maize fields and 93 in pastures. For São Jorge, we recovered 80 pitfalls, 37 from maize fields and 43 from pasture fields.

Quality Control

After collection, specimens were stored in alcohol (96%) before sorting at -20 ºC. Specimens, adults, and larvae were sorted in a laboratory by Mário Teixeira and Mar Calvet and organized the collection in a system of morphospecies.

Method steps

1. Final identification was done by Paulo A.V. Borges.

The following phylum, classes, and orders are covered in this study, although our scientific focus is the phylum of Arthropoda. Phylum Arthropoda: Arachnida: Opiliones; Diplopoda: Julida, Polydesmida; Insecta: Archaeognatha, Coleoptera, Dermaptera, Diptera, Hemiptera, Neuroptera, Orthoptera; Malacostraca: Amphipoda, Isopoda. Phylum Platyhelminthes

1. Arthropoda
   common name: Arthropods rank: phylum

The study was conducted on São Miguel and São Jorge, two islands of the Archipelago of the Azores (North Atlantic). São Miguel Island is situated in the oriental group (37.780411, -25.497047) and is the largest island of the archipelago with 746.8 km² and a maximum altitude above sea level of 1103 meters. São Jorge Island is situated in the central group (38.627778, -28.017222) and is the fourth largest island of the archipelago with 245.8 km² and a maximum altitude above sea level of 1053 meters