490 RECORD OF SCIENCE FOR 1886. 



ARTHROPODS. 



Crustaceans. 



The land isopod crustaceans. — The isopod crustaceans found upon the 

 laud, aud some of wbich are known un«ler the name of pill-bugs and 

 sow-bugs among the English-speaking peoples, have been studied by Dr. 

 Gustav Budde-Lund, and it seems that the species are quite numerous. 

 Four families have been admitted by Dr. Budde-Lund for the species, 

 and are named by him Onisci, Ligise, Tylides, and S.vspastidffi. By 

 far the best represented of these families is that of the Onisci, or, as it 

 is more generally called, the Oniscidse. Fourteen genera are recognized 

 for the species, and these genera are segregated into two sections, (1) the 

 Armadilloidea, including eight genera, and (2) the Oniscoidea, embrac- 

 ing six genera, and iu addition two or three genera unknown to the author 

 have been noticed. The largest of the genera is Porcellio, to which one 

 hundred and four species are referred, of which eighty-two or eighty 

 four are new, and to this succeed, so far as numbers are concerned, 

 OniscuSy with twenty-six or twenty-eight new species, and Armadillo, 

 with twenty-seven. The family of the Ligite or Ligiidae has eight gen- 

 era and thirty-three well-determined and fourteen doubtful species; 

 that of the Tylides or Tylidse, a single genus, with twelve species; that 

 of the Syspastidje includes only a single species. The total number of 

 species described as members of the four families is " four hundred and 

 four or four hundred and ten, of which three hundred and twelve or 

 three hundred and sixteen are good species, and ninety-two or ninety- 

 four are species unknown to the author, or reputed species. The total 

 number of genera is thirty-six, or (if some be accounted subgenera) 

 twenty-five. (Crustacea isopoda terrestria per familias et genera et 

 species descripta a Gustavo Budde Lund, Havniae, 1885; noticed in Ann. 

 and Mag. Nat. Hist. (5), xvii, pp. 81-84.) 



Arachnids. 



Ant-lilce spiders. — The ants are mimicked by representations of va- 

 rious groups of spiders as well a? of other orders of insects. Prof. T. 

 Bertkau has called attention to a number of such cases. Very frequently 

 the ant like appearance is entirely superficial and disappears on close 

 examination. Numerous hemipterous insects, and especially the AJydus 

 calcaratus, exemplify this kind of mimicry. The resemblance i^ the 

 case of Alydus is, however, due chiefly to the median constriction of 

 the body, the dark brown color, similarity of size, and the slight dif- 

 ference of development between the head and tail. In the spiders 

 the resemblance is often quite close. Among the Attidse the cephalo- 

 thorax and the posterior part of the bodj^ are often proximately equal. 

 In the Drassidae ''there are frequent instances of ant mimicry, as, for 

 instance, in the genera Fhruolithus, and especially Micaria.^'' Among 



