How drain flies manage to almost never get washed away

Area of Science:

• Entomology
• Fluid Dynamics
• Materials Science

Background:

• Drain flies (Psychoda spp.) are common household pests found near drains.
• Their ability to survive water exposure, like sink squirts or toilet flushes, is notable.
• Existing knowledge did not explain this resilience beyond simple behavioral avoidance.

Purpose of the Study:

• To investigate the physical mechanisms behind drain flies' water-evasion capabilities.
• To explore the unique surface properties of drain flies' hair covering.
• To understand how these properties interact with fluid dynamics to prevent wetting and drowning.

Main Methods:

• Microscopic examination of drain fly (Psychoda spp.) hair structures.
• Superhydrophobicity and anti-wetting tests using various water droplet sizes and conditions.
• Analysis of fluid dynamics principles relevant to water interaction with the insect's surface.

Main Results:

• Drain flies possess a previously uncharacterized hierarchical hair covering.
• This covering exhibits superhydrophobicity against large water droplets and pools.
• It also provides anti-wetting properties against smaller droplets and condensation, enabling water escape.

Conclusions:

• The drain fly's survival against water threats is primarily due to its specialized hair covering.
• This surface morphology imparts unique fluid-repelling properties crucial for evading water.
• Findings reveal an exceptional adaptation for coping with diverse aquatic environments, preventing wash-away events.