38 JOURNAL OF ENTOMOLOGY AND ZOOLOGY 



C. Muscular Tissue. The usual arrangement of the muscular 

 layers in the fore-intestine of insects is that of an inner layer of 

 longitudinal and an outer layer of circular muscles. The same 

 arrangement is to be found in the case of the walls of the proven- 

 triculus of most of the forms figured in the literature on this 

 subject. In the proventriculus of Hydropsyche, however, the 

 reverse is true, and the longitudinal muscles lie outside of the cir- 

 cular coat. (Figs. 4, 6, Lm., Cm.) This same arrangement of 

 muscle layers was also found by Vorheis (1905) in the larva of 

 the caddis-fly, Platyphylax designatus. Walker. 



The circular muscle layer is very thick, especially where it under- 

 lies the teeth. It gradually diminishes in thickness posteriorly. 

 The layer of longitudinal muscles consists of fibres which are ar- 

 ranged regularly outside of the circular layer. (Fig. 7, Lm. 1.) 

 In the regions opposite the ends of the valves, the fibres unite to 

 form heavier strands which run the length of the proventriculus. 

 (Fig. 7, Lm. 2.) 



IV. Physiology of the Proventriculus 



In regard to the function of the proventriculus, there are three 

 differing views: 1. That the proventriculus is a grinding organ 

 ("Kaumagen"), either for the hard chitinous parts of the food or 

 for a further trituration of the softer parts. Some of the leading 

 adherents of this view are Burmeister (1832), Dufour (1841), 

 Basch (1858), Graber (1869), Wilde (1877), Miall and Denny 

 (1886), and Bordas (1896). 2. That it acts as a strainer and 

 insures the gradual passage of food into the mid-intestine. This 

 view has among its supporters. Plateau (1874), Eberli (1892), 

 Packard (1898), and Petrunkewitsch (1900). 3. That it is an 

 organ facilitating the passage of the mid-intestinal secretions into 

 the crop, and by its contractions thoroughly mixing these secretions 

 with the food. This view is the most recent, being supported by 

 Deegener (1910) and Ramme (1913). These men believe that it 

 also has a straining function. 



I have made observations on the feeding habits of the Hydro- 

 psyche larva and an extended study of the food. The larva takes 

 both animal and vegetable food, but during the period of its 



