Identifying armored scale insects (Diaspididae) using habitus photos

Armored scale insects (Hemiptera: Diaspididae) are economically important pests of many
agricultural crops and ornamental plants. Given their small size, typically ranging from 1-3 mm,
and protective waxy covers, the preferred approach for identifying armored scale insects is to
slide mount female specimens and examine them using a microscope. However, citizen science
projects like iNaturalist have driven interest for field identifications using ‘habitus photos’:
photos of individuals on their host plants. We assessed the viability of using habitus photo
identifications for armored scale insects through an analysis of 94 specimens from 13 species,
collected from five US states. We photographed the insects on their host plants and identified the
specimens based on habitus appearance, then slide mounted the specimens and conventionally
identified them based on morphology. We compared these identifications for each specimen, and
found that 12 of the 13 armored scale insect species assessed could not be accurately identified
using habitus appearance. However, the habitus identifications of the only invasive species
sampled, Lopholeucaspis japonica, had an accuracy rate of 89.5%. This initial data implies that
invasive species may be more easily identifiable in the field than native species, likely because
they are more distantly related to native species. Therefore, the invasive species share less
characteristics with the native species, appearing more distinctive.