On the scorching planet of Elphrona, located in the Outer Rim, existed a species of fly known as heat-flies, which thrived in the hot climate. These flies possessed prominent, multifaceted eyes that bore a striking resemblance to the eyes of Cyclorrians, a sentient and insectoid species. Bell Zettifar, a Jedi Padawan, frequently observed heat-flies flitting about the corridors of Elphrona's Jedi outpost during his training there in the High Republic Era. Later, in 231 BBY, while on the research vessel Innovator, an Elite-class ship, Zettifar drew a mental parallel between the Cyclorrian technicians on board and the flies he had seen on Elphrona, noting the similarity in their eyes.
The novel The High Republic: The Rising Storm by Cavan Scott references heat-flies; this novel was part of Phase I of the Star Wars: The High Republic multimedia project and was released on June 29, 2021. Before the book's publication, StarWars.com featured a preview on May 21 of the same year, which also mentioned the flies.