longest running atlas program in North America is the Ontario Butterfly Atlas Online, which is supported by the Toronto Entomologists' Association and began collecting data in 1969. Bait stations Transects and open searches are not as comprehensive in tropical locations due to issues such as density of flora and the heigh of the forest canopy. A count system using bait stations with fermenting fruit has been used to assess specific populations. Quantifying observations Participants are encouraged to employ a number of techniques to quantify large aggregations by making estimates of butterflies: concentrated along linear features concentrated in an area of uniform habitat concentrated on certain plants butterflies in flight The number of butterflies can be estimated by the area size they inhabit, for example, in the overwintering population present in Mexico the population expressed in hectares. Butterflies can be counted in their egg, larvae and instar number. Butterflies are sometimes captured, tagged and recovered. The number of tags recovered in a specific area is used to determine population size and direction of flight. See also Butterfly Conservation North American Butterfly Association Lepidoptera migration List of butterflies of Great Britain Monarch Butterfly Biosphere Reserve Animal Migration eButterfly References External links UK Big Butterfly Count eButterfly - North American butterfly reporting NABA Butterfly Counts Monarch Watch Ontario Butterfly Atlas - a dynamic map of 417,000 butterfly sightings in the province (as of June 2020) Butterfly Conservation Europe Butterflies of North America Animal migration Lepidoptera and humans Biological censuses Citizen science