KANOKWAN KLAITHIN’s scientific contributions

Stingless bees (Apinae: Meliponini) exhibit astonishing and unusual behaviours, including tear-drinking or lachryphagy. In this review, we summarize lachryphagy in stingless bees, providing updated insights into their taxonomy, foraging patterns, ecology, hosts, evolutionary origins, and potential for pathogen transmission. In Northern Thailand, marked workers of the minute stingless bees Lisotrigona cacciae (Nurse) and L. furva Engel repeatedly return to human eyes, harvesting tears in short bouts that can last for hours or even over multiple days. Behavioural evidence suggests the presence of specialized tear collectors within these species. Single, experienced individuals can harvest tears gently, going unnoticed by the host, though large congregations can become bothersome. Lachryphagy occurs year-round and appears to be driven by high protein content in tears, in addition to salt and water. While Lisotrigona also visit flowers for nectar and pollen, tear collection may supplement or even replace pollen protein when floral resources are scarce or absent in their restricted habitats. Confirmed hosts include humans, zebu, dogs, cats, rabbits, chickens, and yellow tortoises. Lachryphagy has also been reported in other species of Lisotrigona in India. Interestingly, the similarly minute and widespread Tetragonula fuscobalteata (Cameron) is not lachryphagous but sucks sweat, as do other stingless bees, including Lisotrigona, though all visit flowers. This review also examines the potential for pathogen transmission via tear-drinking, particularly concerning viruses entering through the ocular surface, and discusses the evolutionary origins of lachryphagy in stingless bees.