1 80 Lecaniince. 



When the number is eight, two of them are usually much shorter 

 and finer than the remainder, which project beyond the mouth of 

 the sac. The ventral lip of the sac often bears four short hairs, 

 which are sometimes confused with those of the anal ring, giving 

 rise to the statement that certain species possess ten hairs on the 

 setiferous ring. Another common cause of error originates in the 

 fact that the eversile sac is. itself delicately fluted, producing the 

 appearance of a number of parallel hairs springing from the anal 

 ring (//. LXXXI.7?^. 9). The ring also bears a number of 

 glandular pores secreting a waxy material which coats the hairs, 

 and is sometimes produced into long curling filaments, as in 

 L. caudatum. Some scattered spinnerets are usually noticeable 

 on the venter, around the genital orifice (//. \J¥A.fig. \-Ji). 



The dorsum often exhibits a more or less definite pattern, 

 formed by cells in the thickness of the derm. These dermal 

 cells may be scattered and rounded, or densely packed and poly- 

 gonal. They communicate with the surface by a minute pore. 

 When no definite cells occur, the minute translucent pores are still 

 nearly always present. They are probably concerned in the 

 secretion of a varnish- like surface film. It should be noted 

 that the distinctness of the dermal cells varies very considerably 

 in different individuals. In the older and more chitinous indi- 

 viduals, they are usually more clearly defined than in the early 

 adult insects. The cells, in some species, can be demonstrated 

 only after careful preparation and adjustment of light. Staining 

 will sometimes distinctly show cell- markings that were indis- 

 tinguishable in an unstained preparation. On this account it 

 is important that determination of species should be made only 

 after study of a long series of examples. In the soft-bodied 

 species, such as L. Jiesperidnm and L. viride, the dermal cells are 

 particularly difficult to bring into good definition. Even in such 

 strongly marked species as L. nigrum or L. heniisphcsricuvi, I have 

 seen preparations of the early adult female in which all traces of 

 cell-markings had been lost. Too long immersion in boiling 

 potassium hydrate in the course of preparation may bring about 

 this result. Besides the derm cells, there are often lighter and 

 darker spaces formed by differences in the density of the derm. 

 These are often particularly conspicuous on the area surrounding 

 the anal operculum. In a few species {e.g., L. antidesiiKZ) circum- 

 scribed glandular depressions occur on the dorsum. In many of 

 the flatter species, and particularly in the section with flabelliform 



