128 



NATURAL HISTORY OF ARTHROPODS. 



FIG. 187. Polydesnms, enlarged. 



with even fewer segments (nine to eleven), and but thirteen pairs of feet. The species 

 are all minute. The remaining family, GLOMEKID^E, which has twelve or thirteen 



segments, and from sev- 

 enteen to twenty-one 

 pairs of legs, is not rep- 

 resented in the United 

 States. 



Mr. Scudder has pro- 

 posed the name AECHI- 

 POLYPODA for a group of 

 fossil myriapods, which, 

 while closely related to 

 the Chilognatha, show 

 several important points 

 of difference. The dor- 

 sal part of each segment 



(tergum) is much smaller than in that group, and is armed with huge spines. The 

 sterna are proportionately very large and bear between the bases of the feet peculiar 

 crater-like cups, supposed by Mr. Scudder to be the possible supports for gills, but 

 more probably they are comparable to the similar openings on the ventral surface of 

 Scolopendretta. While Mr. Scudder considers the group as a sub-order, Dr. Packard 

 thinks that the characters are of not more than family rank. Almost all the known 

 forms come from the carboniferous, of Mazon Creek, 111., a few having been found in 

 Great Britain. 



ORDER II.--PAUROPIDA. 



This group, which was first recognized by Sir John Lubbock, the banker-naturalist 

 of London, forms, to a certain extent, a connecting link between the chilognaths and 

 chilopods, while in many respects it is distinct from both. There are but six segments 

 in the body behind the head, while the antenna? are greatly different from anything 

 found in the whole class of insects, the basal joints bearing three flagella. Two well- 

 marked types, represented by four species, are found in America, -fauropus, with a 

 rounded body, and Eurypauropus, in which the lateral edges of the body are so 

 expanded as to completely hide the feet. These forms, which live in damp places, are 

 very minute, about one twentieth of an inch in length. The young are hatched with 

 three pairs of feet. 



ORDER III. CHILOPODA. 



This order contains those flattened forms to which the name Centipedes is most 

 applicable. They have long, many-jointed antennae, and but a single pair of limbs to 

 each segment of the body. They are predacious in their habits, moving rapidly, and 

 living largely upon animal food. Many of the forms are poisonous. They have 

 poison glands in the base of the first pair of legs, which are so modified as to lead 

 to their being formerly regarded as mouth-parts, these poison glands emptying by 

 ducts which terminate in the same way as the similar organs in the spiders. 



In the GEOPHILID^E the segments are similar and very numerous, varying from 

 thirty to two hundred ; the eyes are lacking ; the antennae are fourteen-jointed, and 

 the legs are short, terminating in single-jointed tarsi. As indicated by the name, 



