Ebikoola bigenderera kutega oba kukwata kitangaala ate era birina obutuli omuyingizibwa n’okufulumizibwa amazzi n’empewo. Ku ngulu kw’ekikoola kuliko olububi lw’oluzigo oluyitibwa kyutiko (cuticle) olukuuma ekikoola. Mu kikoola mubaamu veeni (veins) ezitambuza amazzi n’ebiriisa munda mu kikoola.