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Annals Entomological Society of America [Vol. VI, 



against the surface a sucking disk is formed. In the lamellae 

 and in the fimbriate gill above, the tracheae absorb oxygen 

 from the water constantly flowing over them. An adhesive 

 apparatus is thus coupled with an efficient respiratory organ. 



The Food of the May -fly Nymphs. 

 May-fiies are almost entirely herbivorous. Their food 

 consists chiefly of fragments of higher plant tissue, algae and 

 diatoms. The following table contains the record of an ex- 

 amination of the stomach content of several nymphs. With 

 the exception of Siphlurus and Chirotonetes the examinations 

 were made upon fresh material: 



Stomach Contents of Nymphs Examined Through April and May. Crosses 

 (X) Represent Substances Found in More Than Ten 

 Specimens of a Genus. 



1. Fragments of Plant Tissue. 



Stems, decayed leaves. 



Epidermis 



Epidermis, moss 



Epidermis, roots 



2. Filamentous algas. 



Vaucheria 



Spirogyra 



Mougeotia 



Ulothrix 



Zygnema 



3. Diatoms. 



Navicula 



Fragellaria 



Tabellaria 



Cocconema 



Meridion.. .• 



Gonphonema 



Synedra 



4. Animal. ^ 



Mayflies 



Other insects 



X 



ffi 



m 



ffi 



X 



X 



The kinds of algse and diatoms found in the stomach 

 varied a good deal with the locality and date of collection. 

 In certain parts of Cold Brook during March, 1911, every 

 available object was brown with Meridion and the stomachs 



