Transposons threaten genomes by making new insertions. Because of this, every organism has acquired a defence mechanism to suppress their expression. One such mechanism is a small RNA-guided silencing pathway called the piRNA pathway. piRNAs are made from RNA transcribed from distinct genomic regions called piRNA clusters that consist of transposon remnants. Once they are transcribed and exported to the cytoplasm, pathway-specific RNA helicases and nucleases recognise the precursor RNA to make mature piRNAs. The mechanism of how transposon-rich sequences are selected for piRNA production is not fully understood. However, a mechanism known as ping-pong utilises sense and antisense sequence complementary to specifically enrich for transposon piRNAs. This mechanism is highly conserved from Drosophila to mouse to Hydra. However, we discovered that one Drosophila species, Drosophila eugracilis completely lacks the ping-pong mechanism yet abundantly produces transposon piRNAs. In this presentation, we explore mechanisms through which transposon RNA is selected for piRNA production in Drosophila eugracilis. We discuss an alternative yet potentially more universal logic of self-nonself recognition.