Adult Sciarid flies are slender, approximately 2.5 mm in length, and have long legs and antennae. They are weak fliers but can run quite rapidly across the soil surface. Their wings are clear or smokey-colored with no pattern and few distinct veins. However, the females of several species are wingless. They have shiny black head capsules.
The life cycle involves four developmental stages: egg, four larvae, pupa and Adult.The females deposit eggs in the surface layer of the potting compost and these hatches within a few days under warm conditions. . Larvae are clear to creamy-white and can grow to about 1/4 inch long The larvae feed on fungal growth and decaying plant material but some species can also damage the roots of seedlings or tunnel into the base of soft cuttings. When fully fed, the larvae pupate in the soil.
Larvae, however, when present in large numbers, can damage roots and stunt plant growth, particularly in seedlings and young plants. Significant root damage and even plant death have been observed in interior plantscapes and in houseplants when high populations were associated with moist, organically-rich soil.