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You are here: Home / Food Pests / The Look and Behaviour of pests / Water and Moisture

Water and Moisture

No animals can live without water, but some can get by with the water created in their own metabolic processes. The vast majority of terrestrial animals will drink water whenever they have the opportunity. This applies to both insects and vertebrates. The black rat, for example, does not have to drink, but does so anyway. The brown rat, however, cannot endure without water and always stays in the vicinity of some form of free flowing water. Among insects, there are several species that can live and multiply in rather dry locations. Mealworm beetles can survive in very dry flour where the water activity is only 0.01, corresponding to a relative humidity (RH) of 1%.

The insects that can survive in very dry places have developed various protective measures to prevent them from drying out. They may have vapour retardant barriers in the form of thick, wax impregnated exoskeletons. There may be a rational water economy, where the water is used for the dietary digestion in the intestines and the excretion of excess nitrogen will be absorbed and recycled. Opening and closing the breathing holes, depending on whether it is wet or dry in the ambient air is also a method. Finally, the insects react to moisture, or rather the lack of moisture, by seeking out places where evaporation corresponds to the surplus water, which they dispose of. One of the consequences of the latter is that hungry confused flour beetles will choose to stay in more humid air than confused flour beetles that have fed recently.

Pests that live in food do not react to the water rates in goods. Their reactions in a room are determined by the relative humidity, and in the product itself it is the water activity which they respond to. Minor differences in water activity have no significant influence on development time, but the differences can be perceived by insects and can determine where in the products or consignments that the insects gather.

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Henri Mourier
Biologist at Statens Skadedyrslaboratorium
Author of:
"Pests in House and Home"
"Bed Bugs - Bites, Stings and Itches"
"Food Pests"
"Husets dyreliv" (Insects Around the House - Only danish)
"Skadedyr i træ" (Timber Pests - Only danish)
"Stuefluen" (Common Housefly - Only danish)
Latest posts by Henri Mourier (see all)
    Food Pests
    Introduction
    An old problem
    Competition for food
    Pests can ruin stored goods
    Why not just eat the insects
    Some insects are unhealthy to eat
    Allergy to pests
    Transmission of infectious diseases
    Where do pests come from?
    Synanthrope species
    (1) The house dust mite and the sugar mite
    (2) The firebrat and the silverfish
    (3) The German cockroach and the forest cockroach
    (4) The rust-red flour beetle and the confused flour beetle
    (5) The merchant grain beetle and the saw-toothed grain beetle
    (6) The cigarette beetle and the drugstore beetle
    (7) The rice weevil and the granary weevil
    (8) The pharaoh ant and the common black ant
    History of the dark flour beetle
    Pests in bird’s nests
    Mould fauna
    The Look and Behaviour of pests
    Insect appearance
    Internal
    Insect development
    Insect senses
    Behaviour
    Water and Moisture
    Temperature
    What insects live off and live in
    The Air
    Mites
    Bug Indentification
    The various species
    Mites
    The flour mite
    The sugar mite
    The common house mite
    The Lardoglyphus zacheri
    The prune mite
    The cheese mite
    The house dust mite
    The Cheyletus eruditus
    Silverfish
    The Silverfish
    The firebrat
    Cockroaches
    The German cockroach
    The Oriental cockroach
    The brown-banded cockroach
    The American cockroach
    The extermination of cockroaches
    Crickets
    Earwigs
    Booklice
    Butterflies
    The Mediterranean flour moth
    The warehouse moth
    Tropical warehouse moth
    The brown house moth
    The Indian meal moth
    Grain beetles
    The saw-toothed grain beetle
    The merchant grain beetle
    The rust-red grain beetle
    Flour beetles
    The yellow mealworm beetle
    The lesser mealworm beetle
    The dark flour beetle
    The confused flour beetle
    The rust-red flour beetle
    The bolting cloth beetle
    Furniture beetles
    The drugstore beetle
    The cigarette beetle
    Bostrychidae
    The lesser grain borer
    True weevils snout beetles
    The granary weevil
    The rice weevil
    The corn weevil
    Bean weevils
    The common bean weevil
    The coffee bean weevil
    Skin beetles
    The bacon beetle
    The dermestid beetle
    The leather beetle
    The khapra beetle
    The reesa vespulae
    Chequered beetles
    The red-legged ham beetle
    The red-breasted copra beetle
    The black-legged ham beetle
    Spider beetles
    The Australian spider beetle
    The white-marked spider beetle
    The golden spider beetle
    The smooth spider beetle
    Plaster beetles
    Flies
    The common house fly
    The lesser house fly
    Blowflies
    The grey flesh fly
    The cheese skipper
    Fruit flies
    Hymenoptera
    The common black ant
    The pharaoh ant
    Wasps
    Birds
    The domestic pigeon
    The house sparrow
    Prevention and control of birds
    Rodents
    The house mouse
    The yellow-necked mouse
    Mouse prevention
    Mouse control
    The brown rat
    The black rat
    Rat prevention
    Rat control
    Imaginary pests
    Niches of food pests
    A: The Waste Niche
    B: The seed niche
    C: The dead plant niche
    D: The sugary excrement niche
    E: The carrion niche
    Prevention and Control, Integrated Control
    A. Inspection of the company and its environment
    The environment
    The premises
    Examination of raw materials and food on site
    Sampling
    Laboratory methods for detection of pests in food
    B. Statement of the problem
    C. Prevention and control
    1. Proper organisation of the company
    2. Proper operation
    3. Exclusion, proofing buildings
    4. Packaging
    5. Non-chemical control measures
    6. Chemical control
    D: Effective monitoring and communication
    Practical information
    Index

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