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Austin McKay, Carlton, Christopher E.
Feliciana blind ground beetles are minute, soil dwelling ground beetles discovered in 2015 in West Feliciana Parish, Louisiana. Like many subterranean insects and other soil dwelling arthropods, adults lack any trace of eyes or wings. Adults range in length from 1.6 mm to 1.8 mm. The body is uniform medium brown in color. Legs and antennae are slightly paler. The dorsal surface is mainly smooth and shining, except for the head, which possesses an array of fine, mesh like sculpturing that is visible under high magnification. The external appearance resembles many other members of the family Carabidae (ground beetles), but the small size and absence of eyes is diagnostic for the genus Anillinus in Louisiana.
Feliciana blind ground beetles are only known from a few adult specimens, and larvae are undescribed. But, larvae have been described for several closely related species. Full-grown larvae of these species are about 2 mm in length, with narrow, obviously segmented pale bodies bearing a few long hairs (setae) on each segment. Heads are long and parallel-sided, with prominent, forward-projecting mandibles and short antennae. The rear end of the abdomen bears a pair of stiff spine-like processes (urogomphi).
Anillinus is one of the most diverse genera of ground beetles in North America, with more than 60 species described. The Feliciana blind ground beetle is the only species of the genus known to occur in Louisiana (West Feliciana Parish). In fact, the nearest localities of other members of the genus are in northwestern Mississippi and central Texas. New species of Anillinus are frequently discovered but identifying them and determining whether they are new to science or previously described is challenging. Adults are extremely similar in external appearance. They can be divided into two general body types; more convex, relatively shorter species, and more elongate, parallel-sided, flattened species. Microscopic details of the cuticle surface and internal sexual organs must be examined for positive species identifications.
The life cycle of the Feliciana blind ground beetle is undocumented, but some general comments can be made based on other members of the family Carabidae. As with all beetles, the species undergoes holometabolous development, meaning each individual undergoes four distinct life cycle stages, egg, larva, pupa and adult. Other related ground beetles and most species in the family Carabidae are predatory. Feliciana blind ground beetles are likely a micropredator of other small soil inhabiting invertebrates, such as mites, springtails, other minute insects and their larvae.
The species was discovered following soil washing (also called soil floatation) of samples dug from a mature hardwood forest located within the Feliciana Preserve Natural Area in West Feliciana Parish, Louisiana. The Feliciana Preserve is a privately-owned nature preserve containing 50 hectares (approx. 120 acres) of relatively intact mature mixed mesophytic forest. Soil from the A and B horizons (mixed organic and mineral layers infiltrated by herbaceous and woody plant roots) was placed in buckets and flooded with water. The material that floated to the top included plant debris, roots and various small animals that also floated and became mixed with it. This material was skimmed off and the organisms were extracted using Berlese funnels. These devices use heat and dehydration to drive the organisms into small bags of preservative, after which they can be identified and studied. The species is currently known from an area less than 0.5 hectare in size, but it likely also occurs in other remnant stands of mature mesophytic forest in the region.
The discovery of a species of Anillinus in the Feliciana Hills of Louisiana is of considerable significance biologically. The region has long been recognized as an area that experienced a relatively moderate climate during the Pleistocene Epoch, 2.6 million to 12,000 years ago. Some plants and animals were able to survive glaciation events in these habitats (Pleistocene refugia) by migrating south in response to glacial advances to the north, a process that required many thousands of years during each glacial cycle. Some species remain as modern relicts and provide evidence of biological distribution changes during past climate cycles. The Feliciana blind ground beetle has evolved into a distinct species with an extremely limited distribution (microendemism). Relictual plant species are more thoroughly studied than insects, but emerging studies of forest litter and soil faunas are beginning to reveal new data about Louisiana’s fauna of Pleistocene relicts. Only a few isolated patches of mixed mesophytic flora remain of a continuous belt that once extended along hills and ravines paralleling the Mississippi Valley north as far as Tennessee and Missouri. These isolated habitats are under threat from timber harvesting and urban deforestation. Recognition of the biological importance and potential threats to populations of Anillinus felicianus prompted its recent addition to the Louisiana Wildlife and Fisheries Commission’s List of Greatest Concern in its Louisiana State Wildlife Action Plan. Further studies of Louisiana’s soil arthropod fauna using soil washing and similar sampling methods can identify hotspots of relict faunal diversity that may guide additional conservation efforts to preserve them.
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Harden, C.W., and M.S. Caterino. 2024. Systematics and biogeography of Appalachian Anillini, and a taxonomic review of the species of South Carolina (Coleoptera, Carabidae, Trechinae, Anillini). Zookeys 1209: 69-197.
Owens, B.E. 2025. Feliciana Preserve Natural Area. (accessed 29 August 2025).
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Sokolov, I.M., and K.E. Schnepp. 2021. A new subterranean species of Anillinus Casey (Carabidae, Trechinae, Anillini) from Florida. Subterranean Biology 39: 33-44. (accessed 4/10/2025).
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4/29/26
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Feliciana blind ground beetle (Anillinus felicianus), dorsal (left) and lateral (right) views. Photo by Chris Carlton, Louisiana State Arthropod Museum
Other deep soil arthropods collected with Feliciana blind ground beetles. Photo by Chris Carlton, Louisiana State Arthropod Museum
