De Silva was born in 1940 and has spent more than sixty years counting, describing and defending the island's reptiles and amphibians. In the 1960s he convened Sri Lanka's first herpetological conference. In 1990 he founded the Amphibia and Reptile Research Organization of Sri Lanka. He started the journal Lyriocephalus, named for the hump-nosed lizard that lives nowhere else on earth. He co-chairs the IUCN Amphibian Specialist Group, and in 2019 received the IUCN Sir Peter Scott Award of Conservation Merit.
The work was never only taxonomy. Sri Lanka has more than a hundred snake species, and roughly five that can kill a person — a ratio that matters enormously to a farmer walking a paddy bund at dusk. An island-wide household survey found that hospital records had been undercounting snakebite deaths by as much as sixty per cent. For decades the country treated envenoming with antivenom raised in India against Indian snakes, a mismatch that cost efficacy and caused adverse reactions. A Sri Lanka-specific product was eventually developed, the first to include the hump-nosed pit viper, an animal long dismissed as harmless until doctors began documenting kidney failure and deaths in its victims.
Seventeen of those lost amphibians were shrub frogs of the genus Pseudophilautus, which hatch straight from egg to froglet with no tadpole stage and so cannot leave the damp leaf litter of the central cloud forests. They vanish when the microclimate does.
What de Silva has built against that is people. Ruchira Somaweera is one of the scientists he mentored; hundreds more across the region have taken his books into the field. In 2019 a day gecko from the foothills of Samanalawewa was named Cnemaspis anslemi after him.
In October the World Congress on Snakes meets in Kandy, on the island whose reptiles he spent his life learning to read.