The fruit fly Drosophila is a research staple — a model organism so widely studied, it would be easy to assume that its lifecycle offered few surprises. But in this week’s issue, Logan Moore and colleagues report an unexpected twist: a parasitic wasp that targets various species of adult fruit fly. Some 200 species of parasitic wasp lay their eggs in vulnerable stages of the fruit fly’s life, attacking larvae or pupae, but until now none had been identified that opted for adult flies as their host. The researchers came across the newly described species of wasp, named Syntretus perlmani, by chance, while screening wild fruit flies for nematode infections in Mississippi. The team determined that the wasp is a member of subfamily Euphorinae, species of which are known to target other adult insects, including beetles, ants and grasshoppers, but this is the first species found to target adult flies. The cover shows the wasp (right) and its host, in this case Drosophila affinis.

Powerful jets of radiation and particles generated by supermassive black holes can affect the distribution of matter and magnetism in the cosmic web — the large-scale structure of the Universe. In this week’s issue, Martijn Oei and colleagues report the discovery of the largest known jet structure originating from a black hole. Identified from radio images, the jets in the structure extend for about 7 megaparsecs (23 million light years), putting it on a truly cosmological scale. Named Porphyrion by the researchers, the structure is captured on the cover in an artist’s impression that shows Porphyrion emerging from a filament of the cosmic web and shooting its jets into the surrounding voids.

The cover shows some of the imposing moai statues on the island of Rapa Nui (also known as Easter Island), one of the most remote inhabited places in the world. People have been living on the island from at least the thirteenth century, but key aspects of its history remain controversial, in particular whether the inhabitants were responsible for ‘ecocide’ — over-exploiting their natural resources and so inducing a self-inflicted population collapse in the 1600s — and whether there was any contact between the Polynesian ancestors of the inhabitants and Indigenous Americans. In this week’s issue, J. Víctor Moreno-Mayar, Anna-Sapfo Malaspinas and colleagues suggest answers to both these questions. By analysing the genomes of 15 people who lived on the island between 1670 and 1950, the researchers infer a steadily growing population that would have declined only after Europeans arrived in 1722 and the Peruvian slave raids of the 1860s, thereby providing no evidence of a self-imposed population decline in the seventeenth century. They also found evidence that the ancient Polynesians who peopled Rapa Nui interbred with Indigenous Americans between 1250 and 1430, long before Europeans reached the island.

Atomic clocks, which use the movement of electrons from one energy level to another to measure time, are the current standard for time-keeping. Nuclear clocks, which would be based on transitions between nuclear energy levels, are expected to offer even greater precision. But it has proved difficult to probe precisely transitions between nuclear quantum states with an external laser — the key step needed to create a working clock. In this week’s issue, Chuankun Zhang and colleagues solve this problem, presenting a direct link between transitions in a nucleus and those in an atomic clock, thereby demonstrating the components needed to create a nuclear clock. The researchers first embedded a thorium-229 nucleus in calcium fluoride crystals (as visualized in the cover image). They then excited the nucleus using vacuum ultraviolet light from a laser they custom-designed and built whose frequency was referenced to today’s most precise atomic clock. The quantum states of the nuclear transition were resolved, providing insights into the nuclear structure. The frequency of the transition was directly compared to the atomic clock, offering a precise point of reference and so making nuclear clocks a practical reality.