NUS researchers discover two new rare species of 'baby-killer' flies

Two new, rare species of Pseudogaurax frit-flies have been discovered in Singapore by NUS researchers. Pseudogaurax are known predators of the eggs and young of other insects and spiders.

Pseudogaurax is an unusual genus of flies in the frit-fly family (Chloropidae). While most frit-flies feed on plant or decaying organic matter, species of Pseudogaurax flies are known “baby-killers” — whereas the adults are harmless and feed on nectar and other organic matter, the larvae are known predators of the eggs of spiders and praying-mantises, as well as the pupae of certain moths and the larvae of leaf-cutter ants. Recently, Dr Yuchen Ang from the NUS Lee Kong Chian Natural History Museum and Dr Barbara Ismay, an entomologist from the U.K., have discovered two more species of this peculiar genus: Pseudogaurax sexnotatus and P. striatus. The researchers published their results in the Raffles Bulletin of Zoology on 2 August 2019. 

These flies are extremely hard to find — only one specimen of each species has been found amidst a thorough, three-year, nation-wide insect biodiversity discovery project under the ‘Biodiversity of Singapore’ initiative that had already processed over 10,000 insect specimens upon their discovery. They are also the first two species to be described from Southeast Asia; a few specimens of undescribed species within the region are also known from Peninsular Malaysia, Borneo, Java, Sumatra and Luzon, but are often preserved in conditions inappropriate for research. Elsewhere, only 60 or so species are known world-wide, and there are likely a lot more species that remain to be discovered.

So how did the researchers manage to isolate these two new species out of over 10,000 specimens? In the past, taxonomic researchers would have had to physically ‘eye-ball’ each specimen to sort and identify them to species — an extremely tedious affair if you are considering going through 10,000 specimens. Fortunately, recent advancements in DNA-sequencing technology (popularly called Next Generation Sequencing or ‘NGS’) have allowed them to sequence large numbers of specimens quickly and cheaply, generating a ‘DNA barcode’ for each specimen at an affordable rate. 

These ‘DNA barcodes’ then allow specimens to be grouped together based on the similarity of their ‘barcodes’: specimens of the same species will have the same or very similar ‘barcodes’, and will differ distinctly from specimens of other species. Specimens are then presorted to putative species groups (called molecular operational taxonomic units, or ‘MOTUs’) using bioinformatics, allowing researchers to bypass the tedious initial sorting phase, and go directly into checking the MOTUs for species integrity, identifying known species, and describing new species. This ‘cheap high-throughput’ approach to large-scale taxonomic research was pioneered by the Evolutionary Biology Lab, NUS Biological Sciences (cleverly described as the ‘$1 barcode’ method), and they are continuing to push forward on this front.

The two new species are featured on a digital reference collection called ‘Biodiversity of Singapore’, where more than 150,000 specimens have now been sequenced and sorted into more than 7,000 entries. The site itself is a rapidly growing curated collection based on the efforts of professional scientists and citizen scientists, which has been helmed as the ‘Pokedex of Singapore’s wildlife’, and currently stands at over 14,000 species featured. The photos of the two new species are openly available and users can zoom into these photos to look at the species in more detail here and here.