Netherlands
Parasitic wasps known solely from the Netherlands include Aprostocetus epilobiellus (BHL), Phaenocarpa curticauda (Nederlands Soortenregister), Microterys nederlandicus (fig. 4 at Zootaxa pdf), and Echthroplexiella (or Ectroma) dunensis (fig. 2 at BHL). Other endemic insects include a moth Lemonia batavorum (ResearchGate) and a freeloader fly Phyllomyza pallida (Milichiidae online) (BHL). The Dutch Large Copper Lycaena dispar batava (Nederlands Soortenregister) is an endemic subspecies of butterfly.
A hydroid Eudendrium vervoorti (ResearchGate), a nematode Laimydorus flevensis (p. 11 of IRD pdf), and a recently extinct jellyfish Eucheilota flevensis (Marine Species WM) (flickr) have only been recorded from the Netherlands.
The Dutch Root Vole Microtus oeconomus arenicola (Zoogdier Vereniging) (BIJ12 WM pdf) is an endemic subspecies of mammal.
Vascular plants known solely from the Netherlands include an orchid Epipactis veluwensis (ResearchGate) and several bramble microspecies: Rubus vadalis (Rubus Nederland), Rubus nelliae (POWO), Rubus scoliacanthus (Rubus Nederland), Rubus contritidens (POWO), Rubus horridifolius and Rubus frieslandicus (both at naturtijdschiften.nl pdf) Rubus nemoripetens (natuurtijdschriften.nl), and Rubus scidularum (Rubus Nederland). Dandelion microspecies unique to the Netherlands include Taraxacum drenticum (rtv drenthe), Taraxacum flevoense (GBIF), Taraxacum scalifolium (GBIF), and Taraxacum wijtmaniae (Nederlands Soortenregister). Endemic hawkweed microspecies include Hieracium weverianum (ResearchGate), Hieracium doryphorum (ResearchGate), Hieracium meppelense (GBIF), Hieracium limburgense (GBIF), and Hieracium macrodontophyllum (GBIF).
Fungi known only from the Netherlands includes Entoloma pudens (Fungal Planet WM pdf) and Entoloma occultatum (Fungal Planet WM pdf). Lichens known only from the Netherlands include Hyperphyscia lucida (ResearchGate), Lichenochora verrucariae (BioOne), and Chaenotheca biesboschii (verspreidingsatlas.nl).
For an overview of biodiversity in the Netherlands see ""De Nederlandse biodiversiteit" at (Naturalis pdf).
See also Aruba, Bonaire, Curaçao, Saba, Sint Eustatius, and Sint Maarten.