Feb., '09] ENTOMOLOGICAL NEWS. 50 



Sesia polygon! Hy. Edwards. 



This pretty little red sesian is the only one I have found in 

 San Francisco, and until this season has been considered quite 

 rare here. Formerly I used to take two or three adults per sea- 

 son, but this year the discovery of its larval food-plant yielded 

 me a fair series of imagines. On the 7th of July, while hunting 

 Lepidoptera a few miles south of San Francisco, in the Lake 

 Merced region, I noticed a male 5. poly go ni rise heavily from 

 a Polygonum paronychia, a prostrate perennial which forms a 

 carpet over the sandy soil in which it grows. I netted this 

 freshly hatched moth, and upon examining the plant found its 

 crown badly infested with a borer, which proved to be poly- 

 goni. However, the season for adults was rather past and 

 but one or two larvae and pupae were procured here. On 

 examining other Polygonum plants I found them very gener- 

 ally infested. A majority of the moths had already emerged, 

 but I found quite a number of pupae and some larvae. An in- 

 fested plant was readily detected by the quantity of pale red- 

 dish brown frass about the base, and frequently by its sickly 

 appearance. Large plants sometimes contain two larvae apiece. 



The larva (Fig. 3) is quite slender; head brown; body dull 

 dirty white, dorsal line dark, cervical shield weak, pale brown. 

 Length of mature larva about 17 mm. The arrangement of 

 the hairs and plates is shown in Figs. 4 and 5. 



The pupa is rather slender, pale brownish, with the more 

 heavily chitinized portions darker, and as in other members 

 of this family is armed with abdominal rows of spines and a 

 pointed process over the head. Length 12 mm., width 3 mm. 



As the smaller stems of Polygonum frequently contain 

 smaller mines (see Fig. i, upper portion), it is probable that 

 the larvae first work their way downwards, often boring far 

 down into the main root. Deserted galleries are found to be 

 filled up with frass; this is probably done in a great measure 

 when the larva prepares its pupal chamber. This is usually of 

 considerable length, the longest measured is illustrated in 

 Fig. I and is 55 mm. long. Others measured were 54, 53, 50, 

 45, 45, 41 and 35 mm. respectively. Small stems containing 



