"Humidity" - what is it, definition of the term
The quantity of water vapor mixed with air, measured as the ratio of the actual vapor pressure to the saturation vapor pressure at a given temperature, indicates how much moisture the atmosphere holds; this ratio can be expressed as a percentage (relative moisture) or as an absolute mass of vapor per unit volume (absolute moisture), and it directly influences evaporation rates, thermal comfort, and the activity levels of arthropods such as ticks, insects, lice, and fleas.
Detailed information
Atmospheric moisture influences the physiological processes of ectoparasites such as ticks, true bugs, lice, and fleas. Measurement typically involves relative water vapor concentration expressed as a percentage of the maximum amount the air can hold at a given temperature. Instruments include hygrometers and psychrometers, which provide precise readings for environmental monitoring.
Ticks require a specific range of water vapor to maintain hydration during off‑host periods. Low levels accelerate desiccation, reducing survival rates, while moderate levels support questing activity and increase the likelihood of host attachment. Laboratory studies indicate optimal survival at relative moisture between 70 % and 85 % at temperatures of 15–25 °C.
True bugs, including many hemipteran species, exhibit varying tolerance to atmospheric moisture. Species inhabiting leaf litter or soil surface depend on higher moisture to facilitate egg development and nymphal molting. Conversely, some aerial predators thrive in drier conditions, where reduced water vapor minimizes fungal pathogen risk.
Lice, being obligate ectoparasites, experience direct exposure to host skin moisture. Ambient water vapor affects the rate of egg hatching; elevated levels shorten incubation periods, while dry air prolongs them. Control measures often manipulate indoor moisture to disrupt life cycles.
Fleas demonstrate rapid water loss when environmental moisture drops below 50 %. Their larvae, which develop in the host’s bedding, rely on sufficient humidity to prevent dehydration. Maintaining relative moisture around 60–75 % in infested areas hampers larval development and reduces adult emergence.
Key considerations for managing these arthropods include:
- Monitoring ambient water vapor levels regularly.
- Adjusting indoor climate to fall outside the optimal moisture range for each species.
- Using dehumidifiers or humidifiers as part of integrated pest management strategies.