Good alpha taxonomy is central to biology. On the basis of a survey of arthropod studies that used multiple disciplines for species delimitation, we evaluated the performance of single disciplines. All included disciplines had a considerable failure rate. Rigor in species delimitation can thus be increased when several disciplines chosen for complementarity are used. We present a flexible procedure and stopping rule for integrative taxonomy that uses the information from different disciplines separately. Disagreement among disciplines over the number and demarcation of species is resolved by elucidating and invoking evolutionary explanations for disagreement. With the identification of further promising study organisms and of new questions for in-depth analysis, evolutionary biology should profit from integrative taxonomy. An important rationale is clarity in researcher bias in the decision-making process. The success of integrative taxonomy will further increase through methodological progress, taxonomic training of evolutionary biologists, and balanced resource allocation.

Diplura is a group of entognathous hexapods, often considered a sister group to insects. They play an important role in recycling organic matter in soil and subterranean terrestrial ecosystems. The Campodeidae is the most diverse family, divided into four subfamilies. The subfamily Plusiocampinae has a subterranean life-style with many species distributed in the Euro-Mediterranean area. The incertae sedis tachycampoids (“lignée Tachycampoïde”) is a group within the family Campodeidae that share with the Plusiocampinae a strong preference for subterranean habitats and several morphological characters, such as slender body shape, elongated appendages, considerable increment in the number of antennomeres and cercal articles, and complexity of sensorial structures. The present monograph provides a taxonomic revision of the subfamily Plusiocampinae and the genera belonging to the tachycampoid lineage from Europe and the Mediterranean region. It comprises detailed morphological descriptions and illustrations together with data on the habitats and distributions of 87 species, 10 subspecies and 11 affinis forms. Seven new species are described among those, namely: Plusiocampa (Plusiocampa) apollo Sendra, Giachino & Vailati sp. nov., P. (P.) chiosensis Sendra & Gasparo sp. nov., P. (P.) dublanskii Sendra & Turbanov sp. nov., P. (P.) hoffmanni Sendra & Paragamian sp. nov., P. (P.) rhea Sendra sp. nov., P. (P.) ternovensis Sendra & Borko sp. nov. and P. (Venetocampa) ferrani Sendra & Delić sp. nov.

Current knowledge of the taxonomy and distribution of European cave palpigrades largely rests upon incidental records. Samples seldom comprise more than one or two specimens, and many regions have only been unevenly explored, if at all. The present study is the first to investigate morphological variability within, and differentiation between, subterranean palpigrade populations in a small, geographically coherent area. It is based on relatively abundant material from six localities in the SW Alps (Piedmont, Italy) and two non-Italian comparative localities. Discrete and continuous characters reveal, on the one hand, a close grouping within the Eukoenenia spelaea species-complex, and, on the other hand, a remarkable short-range endemism. The occurrence of five distinct morphologies in a SW Alpine area of just 2000 square kilometres or so indicates that subterranean biodiversity parallels the rich above-ground biodiversity there. The Cottian Alps in the North harbour E. roscia Christian sp. n., E. lanai Christian sp. n. and the widespread E. spelaea. Two caves in the Maritime and Ligurian Alps are populated by E. bonadonai, which was originally described from the Provence Alps, while the Bossea cave in the Ligurian Alps remains the only known locality for E. strinatii. We evaluate the traditionally employed morphological characters and those recently proposed for use in Eukoenenia systematics. Further, we provide data on the formerly undescribed females of E. strinatii and E. bonadonai, and provide comprehensive pictorial information on the SW Alpine cave palpigrades to set new benchmarks for the taxonomy of the E. spelaea species-complex.

Eukoenenia vargovitshi sp. n. is described after a male from Nizhnyaya Shakuranskaya Cave, Abkhazia, Western Caucasus. The troglobiont species shares a peculiar and probably apomorphic character state with Eukoenenia pretneri from a cave in southern Croatia. The type locality of E. vargovitshi lies in the middle of a large area without previous palpigrade records, extending from Romania and Greece to northern India.