Scientists believe further research is needed into the Fonseca’s seed fly, which so far is believed to only exist on the shores of the Dornoch Firth.
A study commissioned by Scottish Natural Heritage (SNH) was carried out on the fly, known as Botanophila fonsecai in Latin, which is a UK Biodiversity Action Plan (BAP) listed species.
A report by Dr Athayde Tonhasca, of SNH, said fewer of the species were recorded in the latest survey, compared to those made in the 1970s and 80s.
It states that this could indicate a decline in numbers, or that the latest survey missed the insects’ peak activity, the report said.
Larvae were found at the site, but researchers said they may have been those of a similar-looking species.
The report said: “The global distribution of the BAP-listed Fonseca’s seed fly (Botanophila fonsecai) is believed to be restricted to a strip of sand and sparse herbage about 100-m long and a few metres wide on the north shore of the Dornoch Firth.
“As a putative endemic, B. fonsecai should be one of Scotland’s biodiversity priorities, in accordance with the Rio Biodiversity Convention.
“Because of its limited distribution, B. fonsecai population is intrinsically small, therefore subject to random demographic fluctuations and environmental vicissitudes.
“Consequently, B. fonsecai is particularly susceptible to extinction. Moreover, its habitat is subject to trampling caused by recreational activities as well as to natural geo-morphological degradation typical of soft, coastal habitats.
“The protection of this anthomyid fly requires knowledge about its life history so that requirements can be translated into management advice.”
The report recommends trapping flies and also looking for Fonseca’s seed fly at other places with suitable habitat.
Potential sites have been indentified near Brora, Keiss and Durness in the Highlands and dunes between Lossiemouth and Aberdeen.