Who needs eyes in the underworld? – Shedding light on a cave beetle
The deep, dark world of caves harbors fascinating animals unseen by most. Meet Anthroherpon cylindricolle thoracicum, a cave beetle that has adapted to life underground in extraordinary and captivating ways.

The cave beetle Anthroherpon cylindricolle thoracicum. Image: © Dragiša Savić
Profile
- Anthroherpon cylindricolle thoracicum is a cave beetle known only from a few caves on Romanija mountain in Bosnia and Herzegovina.
- This 5.5 mm long beetle is completely adapted to subterranean habitats and can’t survive above ground.
- Due to adaptation to living below ground, the beetle’s body shape is unusual in comparison to species from the same family living above ground. Also, it is blind, depigmented, and it has very elongated legs and antennae.
- It is saprophagous, which means that it feeds on decomposing materials on the walls of caves.
- The lifecycle of these beetles is unknown.
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Classification
- Kingdom
- Animalia
- Phylum
- Arthropoda
- Class
- Insecta
- Order
- Coleoptera
- Family
- Leiodidae
- Genus
- Anthroherpon
- Species
- Anthroherpon cylindricolle thoracicum
Very rare insect!
The genus Anthroherpon belongs to the Leiodidae family and is the most species-rich genus of the exclusively subterranean subtribe Anthroherponina, comprising 26 species and 55 subspecies.
Beetles of the Anthroherpon genus live exclusively underground and are one of nature’s most intriguing examples of adaptation to a subterranean lifestyle. The Anthroherpon cylindricolle thoracicum subspecies* is quite rare, found only in a few caves. Living in a world devoid of light, the beetles have evolved unique adaptations that enable them to survive and flourish where few other creatures can.
Deprived of light, Anthroherpon cylindricolle thoracicum does not need vision. Instead of eyes, these blind beetles have developed elongated antennae to navigate their pitch-black environment, locate food and potential mates. Their bodies are uniformly pale reddish-brown, the color of pure unpigmented chitin (the substance of which insect exoskeletons are made) since color is not needed in the dark.
Their diet is as fascinating as their habitat: they are saprophagous, meaning they feed on decomposing organic material found on cave walls. Their eating habits give the beetles an unglamorous yet vital role in maintaining the delicate ecosystem of their subterranean homes.
While much is known about their physical traits, the lifecycle of Anthroherpon cylindricolle thoracicum remains an enigma. Scientists continue to study them to understand how they reproduce and develop away from the prying eyes of the surface world.
Adaptation in the dark
The adaptations of cave-dwelling creatures are collectively known as troglomorphy. For Anthroherpon cylindricolle, troglomorphic traits include – apart from lack of eyes and melanin: cuticle* thinning, narrowing of the thorax, loss of flight wings, and elongation of legs and antennae. It is generally considered that the increase in appendage length correlates with the increase in the number of sensory organs (small hairs housing olfactory sensory neurons). The beetles also exhibit so-called pseudo-physogastry, where their abdomen is enlarged and appears to be swollen due to an empty space between the wings and the thin abdominal membrane —a trait that has caused frequent speculation. The currently most accepted explanation is that in this cavity beetles store fat – important for surviving long periods of starvation in caves where there is very little food.

The common morphological adaptations of Anthroherpon species (here: Anthroherpon zariquieyi) to the underground environment: narrow thorax, long antennae, enlarged abdomen. Image: ©Bernard van Elegem
While we often think of cave-dwelling animals as living exclusively in caves, many, like the Anthroherpon beetles, also inhabit networks of tiny fissures and crevices that extend beyond the caves themselves. Their habitat is far vaster, extending into the network of microfissures and crevices inaccessible to humans.
The adaptations and lifestyle of Anthroherpon cylindricolle offer a glimpse into the world of cave-dwelling creatures. These beetles are a reminder that even in the most inaccessible and inhospitable environments, life finds a way to not just survive but to thrive. By studying these remarkable insects, scientists gain valuable insights into evolution, adaptation, and the delicate ecosystems that exist beneath our feet.
*Glossary
Cuticle: Also cuticula. The hard outer layer of the insect's body forming the exoskeleton. It is made mainly of chitin, a polysaccharid.
Subspecies: The term subspecies describes populations of one species that can interbreed but usually live in different areas and vary in certain characteristics. A species scientific name consists of two terms: the genus and the species name. The third term in Anthroherpon cylindricolle thoracicum means that it is a subspecies of Anthroherpon cylindricolle.
Thorax: The middle part of an insect between the head and the abdomen.
References
Culver DC. 1982. Cave life: Evolution and Ecology. Harvard University Press, Cambridge. https://archive.org/details/cavelifeevolutio0000culv
Culver DC et al. 1995. Adaptation and Natural Selection in Caves. Harvard University Press, Cambridge.
Giachino PM & Vailati D 2005b. Nuovi dati sul genere genere Anthroherpon Reitter, 1889 (Coleoptera Cholevidae Leptodirinae). Bollettino del Museo civico di Storia Naturali di Venezia 29: 149–163.
Jeannel R. 1911. Revision des Bathysciinae (Coléoptères, Silphides). Morphologie, distribution géographique, systématique. Librairie Albert Schulz, Paris, 641 p. https://archive.org/details/revisiondesbathy00jean
Jeannel R. 1914. Coleopterorum catalogus, Silphidae: Subfam. Bathysciinae. Pars 60. Junk, Berlin.
Jeannel R. 1924. Monographie des Bathysciinae. Archives de Zoologie expérimentale et générale, 63: 1–436.
Njunjić I et al. 2018. Comprehensive evolutionary analysis of the Anthroherpon radiation (Coleoptera, Leiodidae, Leptodirini). PLoS ONE 13(6): e0198367. 10.1371/journal.pone.0198367
Njunjić I et al. 2016. The cave beetle genus Anthroherpon is polyphyletic; molecular phylogenetics and description of Graciliella n. gen. (Leiodidae, Leptodirini). Contributions to Zoology, 85(3):337-359. 10.1163/18759866-08503005
Njunjić I et al. 2015. Two new species of the genus Anthroherpon Reitter, 1889 from northern Montenegro with notes on the “A. ganglbaueri” species group (Coleoptera: Leiodidae: Leptodirini). Zootaxa, 3915 (3):403–412. https://doi.org/10.11646/zootaxa.3915.3.5