Integrative Taxonomy of the Neglected Life Stages of Nearctic Polycentropus (Trichoptera: Polycentropodidae)

The caddisflies (Trichoptera) are a diverse and ecologically important order of insects comprising over 16,250 nominal species. These holometabolous insects exhibit aquatic immature life stages where they are important components of food webs and aquatic-terrestrial nutrient cycling. The larvae are of particular interest given their reputation as “underwater architects” and their use as sentinels in water quality monitoring programs. Still, alpha taxonomy of the order relies on male genitalic characters, leaving female and immature taxonomy lagging far behind. The Nearctic members of the genus Polycentropus (Polycentropodidae) are a prime example, with 12 of 30 females (40%) and 29 of 30 larvae (97%) undescribed. To help remedy this taxonomic impediment, we use an integrative approach combining mtDNA and morphology to associate, describe, and diagnose larvae and females of Nearctic Polycentropus. Using >350 barcoding fragments of mitochondrial cytochrome oxidase I (COI) from males of known identities and unknown larvae and females, we have molecularly associated 15 larvae and three additional females. Diagnostically informative characters have been identified, including muscle scar patterning, head color and pigment banding, and anal claw curvature for larvae, and shape, orientation, and sclerotization of internal and external portions of the genitalia for females. Ongoing efforts include generating identification tools including discriminatory matrices or dichotomous keys, where possible. Finally, current issues with the identification of Nearctic larval Polycentropodidae genera are briefly discussed in light of new findings.