(1996) Fleas! The most frequently encountered flea species on cats and dogs is the cat flea (Ctenocephalides felis). The dog flea (Ctenocephalides canis) is only occasionally found on dogs. More rarely, hedgehog and rabbit fleas are encountered. The flea is an insect and the life cycle progresses from egg to larva to pupa (cocoon) and finally to adult. A female flea needs to have a blood meal from the dog or cat before she can start to lay eggs. Most fleas will lay between 10-15 eggs per day and these eggs fall from the pet into the surroundings. Therefore wherever the dog or cat goes within the house or garden, the eggs can be deposited, which can be over a very wide area. The flea eggs will hatch within a few days and the resulting larvae can pupate within one to two weeks in favourable conditions. The pupae (cocoons) are extremely resistant to adverse environmental conditions. The adult fleas emerge from the pupae under the influence of stimuli such as vibration, warmth and increased carbon dioxide concentrations. The develop-ment cycle from egg to adult takes as little as two weeks in temperatures of 30°C but seven weeks at 20°C and 3-4 months at 15°C. In the UK this dependence on temperature for the speed of the life cycle means that a typical flea season starts in May with a relatively small number of fleas which gradually build up during the season until they reach a peak in August and September. However, the past few years have seen a change in this trend with vets throughout the UK now seeing fleas all year round. The rate of survival of eggs and larvae is dependent on many environmental factors as well as temperature. Humidity, availability of food and the presence of other insect predators are important. In the UK the most favourable conditions for flea development are to be found inside houses. A myth that unfortunately is still perpetuated is that adult fleas only spend a short time on the dog or cat. In fact the reverse is the case. Once a flea has found a host it tends to remain permanently on the animal because it needs to feed regularly and at short intervals. An important point to note is that pupae that are situated in areas that are not often visited by the pet can remain a source of infestations for many months as they will not hatch until suitably stimulated. An adult flea which is waiting to hatch from the protective case of the cocoon can survive for many months. However once out of the pupal case the flea must generally find a host animal quickly. In an average room, a hatched flea that doesn't find a host will die in about 12 days. In cooler, humid parts of the house it could survive longer. Once on the host (and remember that the flea is normally a permanent resident on the pet) the flea has a relatively short life. It is surprising how efficient an animal is at removing fleas by grooming - particularly cats - and most of the fleas will normally only live 7-10 days on the pet. In the past the emphasis has been very much on preparations to treat fleas on the animal - this is understandable because seeing fleas on the animal is generally what prompts most people to realise they have a problem. However the key to successful flea treatment is being able to control fleas in the home environment. Therefore it follows that if we can control fleas in the environment there is a much reduced need for treating the pet. Indeed the only treatment needed for the pet should be when fleas from outside the home are encountered e.g. from rabbits, hedgehogs and from other infested pets. So, the best way to treat fleas is to treat the pet's home environment. This can be achieved by the use of household sprays to kill adult fleas and larvae. These are applied to all areas where the pet frequents, taking care to follow the instructions on the can. This regime is used in conjunction with regular vacuum cleaning of the house and washing the pet's bedding. Inadequate treatment of the home is the cause of apparent failure of treatment on the animal. Newly hatched fleas jump on the animal as quickly as established fleas are killed by direct flea treatment of the animal itself.