136 



NATURAL HISTORY OF ARTHROPODS. 



that next to the head, especially, is often small and collar-like. In the lowest forms, 



however, such as Anura, the segments are of nearly equal size. The mouth-parts 



are very rudimentary, they are situated mostly within the head, 

 the jaws not being strong and adapted for biting, as in other 

 insects ; hence they only nibble decayed vegetable matter. 

 Our commonest poduran is Tomocerus plumbeus, a leaden gray 

 insect with long feelers. The species of Orchesella are gaily 

 ornamented ; those of Lepidocyrtus are white. The scales on 

 different parts of the body are of different shapes, sometimes 

 becoming hair-like. 



In the SMYNTHURIDJE the body is globular or oval, while 

 the legs are long and slender, and most of them are very 

 prettily colored ; they often occur on flowers. One species is 

 often found in the spring on the flowers of the dandelion. The 



family name is derived from Smynthurus, which embraces our commonest species. 



The species of Papirius are even more minute. 



FIG. 198. Smynthums au- 

 rens, enlarged. 



SUB-OEDER II. - - S YMPHYLA. 



This most remarkable group contains but a single family, SCOLOPENDRELLID/E, and 

 a single genus, Scolopendrella; and because the species have a 

 series of abdominal legs they are frequently regarded as myria- 

 pods. By Mr. Ryder, who first called attention to its remarkable 

 peculiarities, it is considered as the type of an order connecting 

 the winged insects and the myriapods. These singular forms in- 

 habit the same situations as other Thysanurans, and might be mis- 

 taken for the young of our common northern centipede (Lithobius). 

 The Scolopendrella immaculata is found in Europe and the eastern 

 and central United States. The head and mouth parts, as well as 

 the antennas, are like those of Campodea, but there is a series of 

 nine pairs of five-jointed abdominal legs, which give it a rnyriapod- 

 like appearance. We thus see that in Scolopendrella we are deal- 

 ing with a remarkably composite or synthetic animal, which with 

 fundamental thysanurus characters combines features which ally 

 them with the myriapods. As we have already stated, the pos- 

 session of functional abdominal legs by Scolopendrella does not 

 imply that it is necessarily a myriapod ; the feet differ in important 

 respects from those of centipedes, and the presence or absence of 

 abdominal feet is not an ordinal or very important character. We 

 shall see further on that the Cinura (Campodea, Lepisma, etc.) 

 have a series of one- or two-jointed abdominal appendages, which 

 are homologous with the legs of Scolopendrella. At the end of 

 the body is a pair of short, pointed stylets, which are spinnerets. 

 This genus may be regarded as an ancestral type, i. e., it is possible 

 that the winged insects have descended from a Scolopendrella-\ike 

 form. This view is strengthened by the fact that the embryos of 

 many-winged insects have at first a series of abdominal feet, which 

 disappear later on in embryonic life. 



c \ 



FIG. 199. Scolopen- 



