Bat-flies (Diptera, Nycteribiidae) These blood-feeding flies are so highly modified that they are barely recognisable as true flies. Wings are absent and the thorax is so reduced and distorted that the head and long legs arise from its top. They do not lay eggs, but produce fully developed larvae, which are deposited near the bat roost site. A well-used traditional roost will be encrusted with the old puparia of these flies. Three species are recorded from Britain and all are virtually host-specific. They can be identified from Hutson (1984). Guano dwellers Apart from certain stages in the life cycle of some of the ectoparasites, the guano associated with a well established bat roost provides a habitat fora variety of mites and insects. In Britain the associated fauna is very limited, but it has been poorly documented. Some flies (Diptera) previously thought to be very rare have been found to be quite common in this habitat, and further investigation is worthwhile. If you collect guano samples, enclosure in an airtight container will kill any fauna through excess ammonia it is better to keep the samples in a well-ventilated container, e.g. a cloth bag or an insect box with a fine-meshed gauze or muslin ventilation area. The guano should not be allowed to dry out completely. Different insects will require different methods of preparation and storage.