Habitat loss previously brought the species to the brink of extinction. Last year, a survey at Castlemartin found only dead adults of the beetle, raising concerns about the future of the species and its continued presence on the site.
The recent discovery of larvae suggests surveyors managed to find some of the hatchlings from a larger batch of immature beetles. Natural Resources Wales stated that the number and distribution of the beetle larvae seen also supported this finding.
The Short-Necked Oil Beetle depends on solitary bees for its lifecycle and requires a specific habitat to survive, including thick vegetation for shelter and dense flower coverage.
Following the successful find, officials thanked their partners and volunteers for their continued support despite two years passing without a single larval sighting.
The insects typically appear from March to June in flower-rich coastal grassland and sand dune habitats, remaining most active on warm, sunny days.
They were not reported in the UK for almost 60 years after 1948 as habitat loss brought the species to the brink of extinction.
But this year, after three years of searching, experts discovered larvae of the beetle on a small area of the site, suggesting that surveyors had managed to find some of the hatchlings from a larger batch of immature beetles.
Adults can grow up toe 24mm (0.9in) in length and the life span of an adult is approximately one year.
Last year, the survey at Castlemartin found only dead adults of this particular beetle, raising concerns about the future of this species and its continued presence on the site.
The Short-Necked Oil Beetle are dependent on solitary bees for its lifecycle and need a particular habitat to survive, with thick vegetation for shelter and dense flower coverage both essential.