AND ITS ALLIES. » 209 



First Group. — Oviparous, skin soft, spurs of moderate 

 size. This is the central group, including most of the early- 

 species. The spurs are only moderately long, but they form 

 narrow cones and are usually separated by a more or less distinct 

 interspace. P.flaviceps, though short -spurred, essentially belongs 

 here. All the species have dorsal eyes and are oviparous. 

 Nearly half the genus is in this section. The species are 

 P. erythrophthalma, P. roseola, P. citrina, P. megalotrocha, 

 P. hrevipes, P. jlaviceps, P. decurvicornis, P. nemoralis, P. 

 acuticornis, P. rugosa, and P. microps. 



Second Group. — Semi-loricated. The skin of the trunk 

 is very thick and stiff, deeply longitudinally plicate on the dorsal 

 surface, strongly transversely plicate on the ventral surface,, 

 scarcely changing shape during movements, the folds merely 

 permitting of expansion and contraction. The three species 

 known have no eye-spots, are oviparous, and have rather small 

 spurs. The species are P. alpium, P. brycei, and P. humerosa. 



Third Group. — Parasitic species. Large animals with long 

 narrow foot, and large broad spurs. Though, a priori, one 

 might expect that diverse species might take to a parasitic 

 life, it appears in this instance that all the parasitic Philodinae 

 are of one stock. Their resemblances are too great to be 

 ascribed to " convergence." The species in the group are 

 oviparous and without eye-spots, except P. laticomis, which is 

 viviparous and has eye-spots. The parasitism of that species 

 is less pronounced, and it frequently swims free. The species 

 are P. parasitica, P. commensalis, P. laticeps, P. hamata, and 

 P. laticomis. 



Fourth Group. — Short-spurred. The spurs in this group 

 are not only short, but they are of a type common in the genus 

 Callidina, very broad and acuminate, as in C. quadricomifera, etc. 

 The species are oviparous, and P. squamosa is the only one of 

 the group having eye-spots. That species is a kind of waif, 

 and has perhaps no right here. The species are P. plena, P. 

 vorax, P. indica, and P. squamosa. 



Fifth Group. — Long-spurred and viviparous. The spurs 

 are extremely long and slender. Every part of the organisation 



