In this study, we present data on life history, distribution and coexistence among five backswimmer species,Notonecta glauca,N. lutea,N. maculata,N. obliquaandN. reuteri, from 72 waters in a study area on the Swedish west coast. Two temporal life history patterns were found; species reproducing in the autumn (N. reuteriandN. lutea) and those reproducing in the spring (N. glauca N. obliquaandN. maculata). Female backswimmers were generally larger than conspecific males, except forN. lutea, in which the sexes were similar in size. The sex ratio ofN. glauca,N. luteaandN. reuteridid not differ from 1/1. The most abundant species wasN. glauca(49% of the waters inhabited by backswimmers) and thenN. obliqua(19%),N. maculata(14%),N. lutea(10%) andN. reuteri(8%). In all, 972 individuals were recorded. The species were sequenced, with reference to their habitat use (from species occurring in temporal habitats to more stable and complex ones), as follows;N. maculata – N. glauca – N. obliqua – N. reuteri – N. lutea. N. glaucahad the widest habitat distribution pattern. Two species combinations in pools were most commonly found and the five species were never found together. Possible competition among adults, according to their habitat distribution, may occur for:N. glaucawith all species;N. obliquamainly withN. glauca;N. luteamainly withN. reuteri;N. reuterimainly withN. luteaandN. glauca;N. maculatamainly withN. glauca. If body size is an important factor in the competitive ability between individuals, not merely species but also sex and temporal aspects have to be considered. The most intense competition should then exist betweenN. luteaandN. reuterifemales.