120 PEACH. ROOT SPECIES OF PORCELLIO. 



pear in ours. It also has a double row of whitish lines, more or less distinct, 

 towards the outer margin, which in our species is replaced by a single row of 

 whitish spots. Other differences might be specified, but these suffice to show 

 the glabcr distinct from its European analogue. 



The Unspotted Porcellio (P. immacu'atus) is dull blackish brown or 

 leaden brown with faint short pale lines and the middle of each segment rough 

 from elevated granules; under side and legs white or lurid. Length 0.30 or 

 less. This is readily discriminated by its uniform brown color unvaried by 

 spots or stripes save the short longitudinal lines which are so faint as scarcely 

 to be perceived and are frequently wholly wanting. It is also our smallest 

 species. It probably occurs throughout the United States, for I met with it in 

 Illinois, and specimens have also been sent me by Mr. Robertson from west 

 of Arkansas. 



The Striped Porcellio (P. vittatus) is black or leaken blackish with tlio 

 head deeper black and the under side whitish; the segments are rough from 

 elevated granules with their hind margins smooth; along the middle of the 

 back is a row of white spots and another more distinct near the outer margin; 

 these spots are often confluent, forming continuous stripes. Length 0.35. The 

 same pale short longitudinal lines which are common in other species are more 

 or less perceptible in this also. Young individuals are of a pale or even whitish 

 color but show the usual stripes of a more clear white. It is one of our most 

 common species. 



The Mottled Porcellio (P. Mixtus) is tawny yellow variously dotted and 

 spotted with black, and with a row of whitish spots which are often confluent 

 into stripes along the middle of the back and near the outer margin; outer 

 edge pale, at least on the angles -of the segments; segments rough from elevated 

 black granules, their basal and apical margins smooth. Length 0.40. The 

 elevated granules form round and oblong black dots, and often on each side of 

 the back the intervals between them are white, thus presenting short longitu- 

 dinal lines of this color, and in a variety (yariega'us) these lines are confluent, 

 forming a longitudinal row of white blotches between the dorsal and lateral 

 stripes. Sometimes the stripe on the middle of the back is tawny yellow in- 

 stead of whitish. This appears to be the most rare of any of our species. 



The Pretty Porcellio (P. limalus'). Black or blackish, with a stripe 

 each side and the outer margin broadly whitish, and two rows of bright yel- 

 low spots along the back ; the segments rough with raised granules over their 

 whole surface. Length 0.50. This is our most common species, being thrice 

 as numerous as any other. It occurs in abundance in our cellars, and under 

 stones and billets of wood in the yards about dwellings and barns. It is quite 

 variable in its colors. In young individuals the two rows of spots along the 

 back are pale or whitish. As it increases in size they all gradually change to 

 yellow, or one or two of these spots take on a bright yellow color whilst the 

 rest remain whitish, but this yellow color is successively assumed by the others, 

 and in old individuals the whole become of a vivid ochre yellow. Dots of this 

 same color sometimes appear also upon the narrow posterior or caudal seg- 

 ments prolonging the rows to the tip of the body. The following varieties of 

 this species may be distinguished. 



