part of sternum furcasternum Abbr: Fs in ISBN:0-937548-00-6. In apterygote insects, the furcasternum is designated as the area of the thoracic sternum separated from the basisternum by the sternacosta. In pterygote insects, where the bases of the sternal apophyses are approximated on the median longitudinal axis to form the furca, the sternacosta is lost and, hence, the separation of the basisternum and furcasternum is usually obscure. In the pro- and metathorax of the mosquito, however, the apterygote condition is retained and a distinct sternacostal suture (absent in the prothorax of some taxa) separates the basisternum and furcasternum. In the mesothorax, the furcasternum is arbitrarily defined as the area of the sternum bearing the furca. Fortunately, the basisternum and furcasternum of the mesothorax are often separated by a secondary line of inflection anterior and lateral to the apophyseal pit. TGMA:0000454 TGMA:0000454 default_namespace