Two Belgians, a Vietnamese and a Kenyan have pleaded guilty to charges of wildlife piracy after they were found with thousands of ants packed in test tubes in what Kenyan authorities said was part of a trend in trafficking smaller and lesser-known species.

Lornoy David and Seppe Lodewijckx, both 19-year-olds were arrested with 5,000 ants at a guest house, they appeared distraught during their appearance before a magistrate in Nairobi and were comforted in the courtroom by relatives.

They told the magistrate they were collecting the ants for fun and did not know that it was illegal.

In a separate criminal case, Kenyan Dennis Ng’ang’a and Vietnamese Duh Hung Nguyen also were charged with illegal trafficking in the same courtroom, following their arrest while in possession of 400 ants.

The Kenya Wildlife Service said the four men were involved in trafficking the ants to markets in Europe and Asia, and that the species included messor cephalotes, a distinctive, large and red-coloured harvester ant native to East Africa.

The illegal export of the ants “not only undermines Kenya’s sovereign rights over its biodiversity but also deprives local communities and research institutions of potential ecological and economic benefits,” KWS said in a statement.

Kenya has in the past fought against the trafficking of body parts of larger species of wild animals such as elephants, rhinos and pangolins among others but the cases against the four men represent “a shift in trafficking trends — from iconic large mammals to lesser-known yet ecologically critical species,” KWS said.

The two Belgians were arrested in Kenya’s Nakuru county, which is home to various national parks. The 5,000 ants were found in a guest house where they were staying and were packed in 2,244 test tubes that had been filled with cotton wool to enable the ants to survive for months.