In 1967, NASA flew flour beetle pupae on Biosatellite II for 45 hours; radiation and weightlessness raised wing abnormalities in flight from 29.9% to 44.8%

During the fall of 1967, as the United States awaited the next Apollo update, a crew of flour beetles, frog eggs, wheat seedlings and fruit flies was strapped into a NASA capsule. They did not get ticker-tape parades. They got 45 hours of orbit, some radiation exposure, and, for the beetles, some serious wing deformities.

According to the mission report for Biosatellite II's insect experiments, the flour beetle pupae which were sent up in the spacecraft returned with a higher percentage of wing abnormalities, from a pre-flight rate of 29.9 percent to a post-flight rate of 44.8 percent, which scientists attributed to the combined effect of onboard radiation exposure and weightlessness, and not to either factor alone. This is a very technical and very obscure piece of information. It is, however, also one of the first concrete pieces of evidence that being in space isn't just about how spaceflight doesn't just expose the body to radiation; it may also make the body less capable of coping with that radiation.

A satellite full of bugs, frogs and wheat


Biosatellite II was not designed for beetles specifically. On board were 13 separate experiments on insects, amphibian eggs, plants, and microorganisms, all aimed at answering one simple yet fundamental question: is a living cell more or less vulnerable to radiation in the absence of gravity? Biosatellite II was also NASA's first truly successful attempt at a dedicated biology lab in orbit. However, the mission had to be cut short as a tropical storm was approaching the recovery area, yet they managed to bring back enough data to keep scientists busy for years.

The flour beetles (Tribolium confusum) were not collected for their beauty. Beetles grow quickly, their wing abnormalities are easily quantifiable, and their sensitivity to radiation was already well studied on EarthThe beetles were pre-irradiated with X-rays before launch to bring them into their radiation-sensitive range, then exposed to gamma radiation from an onboard source during flight. The flight group showed significantly more wing splitting and blistering than beetles exposed to the same radiation dose on the ground. This implies that weightlessness is a not-so-subtle second stressor, in addition to the radiation, that was acting at a cellular level.

The uncomfortable math

According to a 2013 peer-reviewed analysis titled “How Safe Is Safe Enough? Radiation Risk for a Human Mission to Mars,” published in the journal PLoS One, astronauts on a round trip Mars mission could be subjected to central estimates of radiation-induced mortality risk that surpass NASA’s own acceptable limits, with galactic cosmic rays being the primary culprit since in low Earth orbit those rays are substantially deflected by Earth's magnetic field and absorbed by the atmosphere, protection that spacecraft traveling beyond Earth orbit, such as on a Mars mission, would largely lack. The same basic question then, was, and remains: would radiation damage in space be more damaging than radiation damage alone? And that was precisely what Biosatellite II was designed to determine in 1967, but with more sophisticated instruments and, of course, much higher stakes.

Beetles are, weirdly, back in the conversation

Insects are being seriously considered as a food source for long-duration space missions, and for good reason; they are relatively inexpensive and require little room. A 2025 review article titled “Insects in outer space: assessing the effects of microgravity on edible and model insect species for spaceflight food system,” published in the journal Frontiers in Physiology, notes that although insect development is said to be species-dependent and not consistently affected by microgravity, immune function and physiology could suffer in certain insect species. In other words, the bugs that NASA once used to check for radiation could become dinner for future crews; hence, understanding the effects of spaceflight on insect biology is much more than just an academic curiosity.

The takeaway

More than five decades after Biosatellite II, human spaceflight agencies have developed more detailed models, and a clearer understanding of the interaction between weightlessness and radiation in biological systems, though this remains an active area of research rather than a fully solved problem. In 1967, this 44.8 percent wing abnormality rate in beetles was a warning shot. No one developed a comprehensive human countermeasure based on it and, honestly, shielding of deep-space crews is still under development. As agencies discuss returning to the Moon and eventually sending humans to Mars, the flour beetle's wing deformities remain a useful reminder of how spaceflight can affect living tissue in ways that aren't immediately obvious.