Figure 382. — Photograph of live P. ligni lying quiescent inside a glass tube. Dorsal view. 



per layer of surface 1 square foot in area and 1 

 inch deep. 



Since P. websteri is confined in oysters to mud 

 blisters and does not come in direct contact with 

 oyster tissues, it causes no visible injuries. This 

 view is corroborated by the observations of 

 LoosanofI and Engle (1943), who found that 

 oysters heavily infested with P. websteri and grown 

 in trays above the bottom were in excellent 

 condition. 



However, personal observations made in Seaside, 

 Va. and in Texas bays convinced me that oysters 

 heavily infested by mud worms (fig. 385) are 

 usually in poor condition. This opinion is shared 

 by Lunz (1940, 1941), who calls the mud worm a 

 pest in South Carohna oysters. According to his 



FiGDEE 383. — Drawing of newly emerged larva of P. 

 websteri viewed alive from the dorsal side. From 

 Hopkins, 1958. 



0.25 



Figure 384. — Young "bottom stage" of P. ligni Webster. 

 Modified bristles from fifth segment at left, and ventral 

 hooded crochet at right. From Fauvel, 1927. 



observations, 20.9 percent of the oysters gi'owing 

 on the hard sm-face of tidal flats are infected, and 

 the percentage increases to 51.9 on soft, muddy 

 bottoms above low-water mark. There is no 



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FISH AND WILDLIFE SERVICE 



