Display omitted •The aim of this study was to analyze the chemical composition of larval foam.•Foam was collected from hemipterans from spittlebug.•Chemical composition of foam was identified from 73.76 to 93.21 %.•The analyzed samples consisted mainly of a carbohydrate polymers.•Sugar unit composition of foam was fucose, similar which was isolated from brown seaweed. The aim of this study was to analyze the chemical composition of nymphal envelopes (foam) collected from spittlebugs belonging to the species Aphrophora alni (Hemiptera family Aphrophoridae). Foam was collected in Poland in the Mazowieckie Voivodeship in 2020–2022. Foam was collected from nymphs, feeding on young leaves of black alder trees (Alnus glutinosa), from 12 different areas. For the first time, the chemical composition of the foam produced by the spittlebug was quantitatively analyzed, identifying from 73.76 to 93.21 percent. The analyzed samples consisted mainly of a carbohydrate polymer similar in sugar unit composition to fucoidate isolated from brown seaweed. The most important sugar units identified were fucose (17.0 % − 35.6 % of the dry weight of the secretion), glucose (6.1 % − 16.2 %), mannose (1.5 % − 9.9 %), rhamnose (0.4 % − 1.3 %) and xylose (0.06 % − 0.1 %). In addition, various fatty acids, myo-inositol, pinitol, aliphatic hydrocarbons, waxes and aliphatic derivatives of 2(3H)-furanone were found. The collected foam contained from 0.05 % to 0.1 % of dry matter. Significant changes in the chemical composition of nymphal envelopes were found depending on the year of collection, which is probably strongly related to climate change.