Males about 35–55 mm; females about 55–60 mm.
Fine-art photographic collection
Prionacalus cacicus
A flightless Andean longhorn whose female can outweigh the male while the male carries the longer sensory “horns”.
About this species
Prionacalus cacicus(White, 1845)
Information reviewed15 July 2026
Prionacalus cacicus is an extraordinary prionine longhorn from the western side of South America. It has a black, heavily sculptured body, spined thorax and pronounced differences between the sexes.
Taxonomy
Animalia · Arthropoda · Insecta · Coleoptera · Cerambycidae · Prionacalus
Accepted taxon. · checked 2026-07-15
Ecuador and PeruBroad range and selected reference localities — not a complete occurrence map.
Ecuador and Peru
Andean and foothill forest containing large dead or dying trees.
Principally nocturnal; adults move on trunks and forest floor.
Larvae bore in dead wood; adults of this prionine lineage feed little or not at all.
Solitary.
What makes this species remarkable?
The adult is flightless, so a beetle built like a small armoured machine must climb and walk through steep forest rather than escaping or dispersing on wings.
Females can reach 55–60 millimetres and exceed males in body size, while males carry the more exaggerated antennae — reproductive investment has enlarged different structures in each sex.
Its pronotum is ringed with hard lateral teeth and the mandibles project forward, producing a defensive front end that can brace, pinch and resist handling even though the animal cannot fly away.
Sources and scientific references
- GBIF — taxon record/search for Prionacalus cacicus
- Catalogue of Life — taxon search for Prionacalus cacicus
- Revision of Prionacalus — genus restricted to western South America and redescription of P. cacicus
- Prionacalus cacicus specimen measurements by sex and Peru provenance
- Photographic record explicitly describing P. cacicus as flightless
More photographs
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