Had this on a mailshot today
Cannon Pest Control have the top slot this issue with the October pest of the month - fungus gnats. If you've never heard of them, once you've read the details, we're sure you'll recognise the little blighters! They are blackish, brownish or yellowish in appearance and small at around 5-8mm in size. They are common in houses, buildings and gardens most of the year in the UK, so no doubt you'll have spotted one at some point. At night they are attracted to light and enter buildings through open doors and windows to get to it. They look like mosquitos but have only a short feeding tube for liquids, (not to pierce the skin) and don't bite.
Female fungus gnats lay about 150 eggs which hatch in 4-6 days. After 2 weeks, pupation occurs with adults emerging a few days later. Danger signs are large numbers of flies seen alighting on surfaces in offices and communal areas, especially close to plants. Where the problem is external, they may be found in or around air intake filters. Although harmless to people, these pests can be hazardous in food handling or sterile areas, and their presence can cause psychlogical claims of 'being bitten'. Preventative measures include good hygiene and housekeeping, not overwatering plants, and regularly turning the top 5-7mm of soil in plants.