GREEN TOAD FLY: A DEADLY PARASITE FOR TOADS

During a recent field visit, we encountered a striking and grim example of parasitism: the relationship between the common toad (Bufo bufo) and the green toad fly (Lucilia bufonivora). This fly, which primarily occurs in Northwestern Europe, has a life cycle that comes at the direct expense of its amphibian host.

Extensive tissue damage around the eyes and nostrils, caused by fly larvae feeding on the living tissue. (c) Ellen Blomme

The green toadfly

The adult green toad fly feeds on nectar and pollen, but its larvae adopt a parasitic lifestyle. From May to July, female flies lay their eggs in existing wounds or near natural openings such as the toad’s nostrils or eyes. Once hatched, the larvae begin feeding on the animal’s living tissue. This leads to severe injuries and ultimately the death of the host.

Impact on the toad

Infected toads often show behavioral changes such as disorientation and reduced wariness. The physical damage to the nasal passages and surrounding tissues is extensive and typically fatal. While the common toad is the most frequently affected species, infections have also been reported in other amphibians. The broader population impact of such infestations remains unclear due to a lack of comprehensive research data.

Distribution and research

Although the green toad fly is mainly found in Europe (Strijbosch, 1980; Weddeling & Kordges, 2008), similar infections have recently been reported in amphibians in North America. Research suggests that this parasitic relationship has evolved despite the toxic skin secretions of toads—indicating a remarkable evolutionary adaptation by the fly (Mebs et al., 2014).

Conclusion

The interaction between the green toad fly and its amphibian hosts highlights the complexity—and sometimes cruelty—of nature. Understanding such relationships is crucial for conserving biodiversity and managing vulnerable amphibian populations.