22 SMITHSONIAN MISCELLANEOUS COLLECTIONS VOL. 85 



which rehsh crabs, inchiding hermits, also eat mollusks, bryozoa, and 

 hydroids. What difference is it to them that a molKisk shell con- 

 tains a hermit crab rather than its original occupant, or that hydroids 

 are growing on it when these animals are browsed from rocks, etc., 

 elsewhere? Mcintosh has brought up this same point with regard to 

 species of Hyas which become covered with a growth of algae and 

 invertebrates, yet covered with parasites as they are, abound in 

 stomachs of the cod.'' They are eaten by other fishes and by birds 

 also. Conclusions of a similar nature undoubtedly must be drawn in 

 the case of those crabs associating sea-anemones and ascidians with 

 themselves. Both of these classes of animals have their enemies 

 which probably would engulf crab and all in cases where the animals 

 were together. 



The caprellids noted by Mortensen as resembling algae and by 

 Parker and Haswell as so closely assimilated in form and color to 

 Hydrozoa and Polyzoa as to be difficult of detection nevertheless are 

 detected and eaten by some birds and by numerous fishes, and the 

 protectively formed and colored isopods of the genus Idofhea are 

 represented by 51 records for 6 species in stomachs of 18 kinds of 

 birds. 



The fiddler crabs (Uca), so abundant and conspicuous on the mud 

 flats of the southeastern coast of the United States, have one claw 

 enormously developed, thus having the principal characteristics of the 

 so-called protected species, a special mode of defense, and Hving ex- 

 posed and conspicuously in large numbers. They are freely eaten by 

 birds however and for this single genus of a few species, we have 

 271 records from 24 species of birds. 



Myriapoda (Thousandlegs, Centipeds) 



Protective adaptations. — The centipeds and millipeds exhibit differ- 

 ences that would warrant their being treated as separate classes; 

 customarily, however, they are considered together. The following re- 

 marks on their protective adaptations are quoted from F. G. Sinclair.' 



The means of defence possessed by these animals .... differ very much 

 in the different species of Myriapods. In the Centipedes the animals are 

 provided with a powerful weapon in the great poison claws which lie just 

 beneath the mouth, and which are provided with large poison glands, whicli 

 supply a fluid which runs through a canal in the hard substance of the claw 

 and passes into the wound made by the latter. The effect of this fluid is 



'Ann. Mag. Nat. Hist. 7th ser., vol. 7, p. 229, Mar., 1901. 

 ' Cambridge Nat. Hist., vol. 5, pp. 36-37, 1910. 



