Blow fly larvae socially integrate termite nests through morphological and chemical mimicry

Nests of ecosystem-dominant eusocial insects like ants and termites offer stable, nutrient-rich, and protected habitats that may be exploited by other organisms. Several arthropod lineages managed to breach nest defenses and become inquilines, mutualists, predators, parasitoids, or social parasites.1,2,3,4 However, achieving social integration requires extreme morphological, behavioral, and physiological adaptations.5 Among flies, only scuttle flies (Phoridae) are well-known social parasites,2 although interactions with termites (predation, scavenging, and putative parasitism) have also been mentioned in anecdotal reports for blow flies (Rhiniinae6,7,8,9,10 and Bengaliinae11,12,13) and flesh flies (Miltogramminae14,15,16). Here, we report a fly larva found to be socially integrated within nests of the termite Anacanthotermes ochraceus (Burmeister) in Morocco. Behavioral, chemical, and morphological analyses show that colony integration, including communication and grooming, is achieved through unique adaptations. The chemical profiles of the fly larvae perfectly match those of the termites at the colony level. Notably, the posterior part of the larvae mimics a termite’s head, and the long papillae that imitate the termites' antennae surround the entire body. Based on phylogenomics, we show that the larvae belong to the blow fly genus Rhyncomya (Calliphoridae: Rhiniinae). Our results support the hypothesis that the enigmatic blow fly subfamily Prosthetosomatinae (only known from larvae observed in termite nests17,18,19,20) is Rhiniinae. Thus, we demonstrate that the diverse schizophoran flies evolved social integration independently from the 150-million-year-diverged Phoridae radiation. This discovery sheds light on the repeated evolution of termitophily within the order Diptera.