The Asian tiger mosquito, Aedes albopictus, is a severe threat to human health, and it is one of the world’s worst invasive animal species and carries many viruses. Scientists have been seeking an effective and environmentally friendly control strategy. Riccardo Casini and colleagues in Italy have been examining bladderworts, aquatic carnivorous plants of the Utricularia genus, as a potential biological control solution.

A new study has tested the southern bladderwort, Utricularia australis, as a predator of Aedes albopictus larvae in a no-choice experiment. The team divided the larvae into two size groups: 1st–2nd and 3rd–4th larval instars, an instar being a growth stage for larvae between moults. Twenty Aedes albopictus larvae were placed inside 1-litre plastic cups with a 30-centimetre-long plant segment and left for seven days. The experiments used twelve segments of Utricularia australis, six for each larval size group, counting the number of bladders of each segment at the beginning of the experiment. The 7-day process was repeated five times for each segment/cup over two months, with the number of captured larvae and emerged adults recorded daily.

In total, 84 captured larvae were chosen to measure larval length, percentage of larval body trapped within the bladder, bladder perimeter, and bladder area, to evaluate the ability of the bladders to capture larvae, by complete or partial suction of the body, depending on the relative sizes of larvae and bladders. Results indicated that Utricularia australis is an effective predator of mosquito larvae, with a higher efficiency against the 1st-2nd instar group (72%) compared to the 3rd-4th group (39%). The number of captured larvae depended on the number of bladders on each segment and instar group. The percentage of trapped larval body depended on the relationship between bladder size and larval length.