Species Identification of Wireworms (Agriotes spp.; Coleoptera: Elateridae) of Agricultural Importance in Europe: A New “Horizontal Identification Table”

SIMPLE SUMMARY: Wireworms are soil-dwelling larvae that damage multiple arable crops. The most common wireworms found in European cultivated fields belong to the genus Agriotes. Large amounts of insecticides are applied on a prophylactic basis to control them; before any treatment can be applied, however, legislation imposes an assessment of whether pest population levels exceed a damage threshold above which a significant yield reduction is expected. Thresholds vary greatly among species, thus quick and reliable larval identification is needed. This will result in the implementation of the appropriate integrated pest management practices. Furthermore, research into non-chemical strategies involves carrying out tests with live wireworms identified to species. Wireworms were observed to identify live larvae rapidly on site to assess density and compared with species-specific thresholds before sowing, and for laboratory experiments to be performed. This work led to a “synoptic key” that reliably identifies most live larvae, while traditional keys consider only single characters step by step. The key considers several discriminating morphological characters in order of stability. Identification becomes reliable when at least two main discriminating characters are found and attributed to a single species. ABSTRACT: Wireworms are yellowish soil-dwelling larvae that damage a wide range of arable crops. The most common wireworms found in European cultivated fields (except for the Caucasus) belong to the genus Agriotes (Coleoptera: Elateridae). In several European countries, environment-impacting insecticides are applied on a prophylactic basis to control them. However, before any treatment can be applied, European legislation requires that an assessment is done when pest population levels exceed a damage threshold. The threshold substantially depends on wireworm species, thus quick reliable larval identification is needed to implement the appropriate integrated pest management practices. Furthermore, research into non-chemical strategies involves carrying out tests with live and identified wireworms. Thus, thousands of wireworms were observed in a bid to identify live larvae so that larval density could be assessed and compared with species-specific thresholds before sowing, and laboratory experiments were carried out. This work led to a horizontal identification table that allows for quick and accurate identification of live larvae. This key, unlike traditional dichotomous keys, simultaneously considers a set of multiple discriminating morphological characters in order of stability. The key can be reliably used by less experienced users and, once minimum familiarity is acquired, most larvae can be identified rapidly, with high precision.