50 THE WELSHMAN'S BUTTON 



form a very striking feature of the Welshman's 

 button, and are shown in Fig. 20, whilst the 

 male genitalia appear in Fig. 21. 



FiG. 20. Head of Sericostoma ptrsonatum, <J (Welshman's 

 button) ; M, maxillary palpi ; L, labial palpi. 



FIG. 21. Genitalia of Sericostoma fersonatum, 6 , 

 (Welshman's button) from the side. 



I also give a drawing of the grating with 

 which the larva seals each extremity of its case 

 when about to pupate. The half -moon shaped 

 apertures allow ingress and egress to the water, 



