Starlight glowworm

Larva

Starlight glowworms spend most of their lives in their larval stage. Much of their bodies are transparent, allowing for the chemicals inside their bodies to emit their tell-tale glow. In addition to their light emission organs, starlight glowworms also have developed a silk spinner organ. Each larva spins a nest out of silk on the ceiling of the cave and then hangs down as many as 70 threads of silk (called snares) from around the nest, each up to 30 or 40 cm long and holding droplets of mucus.   A larva's glow attracts prey into its threads. Prey include beetles, flies, mosquitos, moths, and even small snails or millipedes. When a prey is caught by a snare, its larva pulls it up (at up to about 2 mm a second) and feeds on the prey. When prey are scarce, larvae may show cannibalism, eating other larvae, pupae or adult flies.   The glow created is the result of a chemical reaction created in the glowworm's stomach and intestines. This light, while dim, does in fact emit UV radiation at the same wavelengths as the sun's light. Many have noted that this reaction appears to be not only unique in the animal kingdom but likely impossible without some sort of arcane or divine intervention. Some have hypothesized that the Underdark phenomenon known as faerzress may be the reason for such a reaction.  

Adult

Adult starlight glowworms are not worms at all but rather midges with narrow wings, a proboscis, six limbs, and a set of sex organs. These midges live only a few weeks during which time they must breed the next generation of glowworms. Their proboscis is designed to pierce the vascular system of many kinds of mosses, which gives these midges extra stamina during the search for a mate.

Starlight midges lay clutches of between 500-1000 eggs on the ceilings of caves. After laying the eggs, the female midge dies. These eggs are incredibly hardy and have developed the ability to pass through the digestive tract of a purple worm without compromising the embryo inside.

Starlight glowworms have holometabolous metamorphosis with eggs, larvae, pupae, and adults. Individuals spend most of their lives as larvae. These flies live from about 6 through 12 months as larvae, depending on food availability. A larva is only about 3–5 mm long when it emerges from its egg, and can grow up to about 3 cm long.    At the end of the larva stage, it becomes a pupa, hanging down from the roof of the cave. The pupa stage lasts about 1 or 2 weeks and it glows intermittently. The male stops glowing a few days before emerging, the female's glow increases. The glow from the female is believed to be to attract a mate, and males may be waiting there when she emerges.

The integral nature of the starlight glowworm has resulted in the proliferation of dozens of otherwise impossible subterranean ecosystems. However, very few kinds of vegetation are able to be grown under the glowworm's light, and many of them are exclusively symbiotic with a particular species of glowworm. Most of these plants are mosses or lichens, with very few appearing like the green leafy organisms known on the surface. In fact, no known glow light vegetation uses chlorophyll to photosynthesize, resulting in gardens of organisms colored black, indigo, lavender, blood red, royal purple, and milk white. These plants are also quite low in nutritional value compared to those on the surface, however, they remain in high demand by almost all herbivorous creatures in the Underdark.   Despite the glow midges only being able to feed on subterrestrial plant matter, the presence of starlight glowworms also enables the growth of algae and other rare kinds of aquatic plant matter. This allows for the further diversification of trophic levels in the Underdark's many underground rivers and lakes. It also enables some unique species of photosynthesizing microorganisms, such as the cave plankton, the most common creature by biomass in the entire Underdark.

Mortals have found cultivating crops under starlight glowworm biolumenscence to be extremely challenging. One exception has been the development of moon wheat, a special kind of wheat grass that can be in glow light conditions. Known for its pale lavender coloration, moon wheat is grown as a staple crop in many indigenous marked cultures and mortal colonists. It also is the preferred food of the majority of large herbivores found in the Underdark.   Starlight glowworms are also harvested by alchemists and mages specifically for their bioluminescence. The chemicals found in their bodies can be used in the manufacture of various artificial light sources, such as driftglobes, as well as other arcane products.