The brightness of the glow is used by the males as an indicator of female fecundity. Males are more likely to fly to a brighter female, because it is larger and has more eggs. Due to this, females compete against each other for matings. The males are sometimes attracted to man-made light fixtures. The peak glowing period is evenings in June and July. They are found in old-growth grassland, especially on chalk and limestone soils. They are also found in verges, hedgebanks, and on heaths. The larvae live in sheltered places – under rocks and wood, but do crawl over different terrains. Once the females have attracted the males with their glow, they mate, lay eggs, and die. Typically, 50–100 are laid over three days, with the adult not surviving to see them hatch. They are laid in fairly moist places, e.g. stem of grass or under moss. The eggs are pale yellow, 1 mm across. They may glow faintly yellow and take between 27 and 45 days to hatch depending on the weather (colder=longer). The eggs hatch after two or three weeks. Larvae and adult females look similar, but larvae have bright spots on each of 12 segments, whereas adult females have a completely black back. The predatory larvae feed for two or three years on slugs and snails which they inject with a brown, toxic, digestive fluid, delivered by a series of nips and bites. The poison takes a while to work, and the larva has to be careful not to become stuck to any protective mucus that its prey may secrete. The prey is gradually paralysed and the digestive fluid turns part of it into a brown broth that the larva can lap up. The prey remains alive, and some partially eaten victims have been known to crawl away after the meal. The slugs and snails are often 200 times the weight of the beetle larva. The larvae are nocturnal, and are most active during moist conditions, when their prey are most active. The larvae may moult four to five times in their lifetimes. They spend their winters under logs, stones, wood holes, or leaf litter, their bodies drawn in like concertinas, hibernating as their food source becomes increasingly hard to find. They wake up in spring, and the cycle is repeated for one more year, or possibly two. They become adults from May to July or sometimes later, surviving on food reserves built up during time as a larva, and dying after reproducing.