The proper name for these pests is Psocids, but they are more commonly known to most people as Booklice.
Although generally an outdoor creature they do occasionally invade the home (usually in contaminated foodstuffs).
They are harmless to man and are usually only a nuisance value as they contaminate foodstuffs, plant and animal based products. However, occasionally, an infestation can get out of control and they can then cause significant damage to delicate materials such as books and furs.
Booklice prefer high humidity as they thrive on the types of bacteria, yeast, mould, and algae that are associated with damp conditions. They can be seen swarming over furnishings and around bathroom suites and tiles. They will even infest damp plaster on walls & ceilings.
Control
Remove the food from your kitchen cupboards, inspect it and dispose of any infested items. Put non-infested items in airtight containers. The cupboards can then be sprayed with a crawling insect spray but must be dry to the touch before any food is returned and this should be in containers, so there is no direct contact between food and cupboard surfaces. Also spray the floor and other areas where the Booklice have been sighted.
These sprays may have to be applied repeatedly over time before control is achieved.
Make every effort to remove and control moulds and algae around baths and sinks etc.
The most effective method of control is by changing the environment from a damp one to a dry one, thereby stopping the development of the moulds on which Booklice also live.
Always follow the manufacturer's instructions for use on the container.
