Fleas cause serious and irritating bites to all of their victims, all the while, passing on harmful bacteria to both animals and humans alike. They can go unnoticed for weeks, even months, and reproduce at an alarming rate.

Cat flea

Biology : Adult fleas are between 1-3.3 mm long and brownish in colour, with squashed looking bodies. This helps the flea to move through fur and feather. The hind legs of a flea are relatively large and are used for jumping heights of up to 16 cm. Flea eggs are pearl white in colour, oval shaped and approximately 0.5 mm long. The pupa is about 6 mm long , looking like a typical maggot. It undergoes larval moults, gradually increasing in size and changing colour from white to cream. 
The female flea lay several hundred eggs after each blood meal in the cat's fur, or areas where the cat would be found. After several weeks the eggs drop off and hatch into tiny hairy worm-like larvae. Pupa's mature to adulthood within a cocoon woven by the larva to which dust, pet hair, carpet fibres, and other debris adhere. After 5 to 14 days adult fleas emerge from the cocoon. Fleas can live up to 2 months or 1 year without eating but cannot survive or lay eggs without blood. People may be bitten by fleas, especially when populations are high, fleas will not live or reproduce on humans. Many think that pheromones in male humans make them more succeptable to bites than others.

Significance :Fleas can be carriers of disease or may transmit parasitic worms. Fleabites are identified as a small dark red spot surrounded by a reddened area. The bite persists for one or two days and maybe intensely irritating.

Signs of infestation: Fleas are normally brought into the house via pets. You may notice that your pet is scratching itself more than usual. Watch out for insect bites around your own ankles. Look through your pet's hair carefully for fleas and dirt, down to the skin level.                                                      

Facts: The largest ever recorded infestation of human fleas in the UK was found at a pig farm in 1986. It reportedly turned an area the size of a tennis court brown.
63 species of flea are found in the UK. About 10 of those could be found in homes.