74 Miscellaneous. 



The Parasitic Mites of Birds, a Contribution to the Knowledge of the 

 Sarcoptidse. By E. Ehlers. 



The observations of M. Ehlers, which relate to interesting questions 

 of adaptation and heredity, are made upon an Acarian very nearly 

 allied to that described by !M. C. Robin under the name of Sarcoptes 

 mutuns. It is also a bird-parasite, and was discovered on a speci- 

 men of Munia maja, in which it produced excrescences at the base 

 of the beak. For this species and M. Robin's the author establishes 

 the genus Dermatoryctes, which is particularly characterized by the 

 form of the feet in the two sexes. He calls his species Dermatoryctes 

 fossor. 



The female of D. fossor is much larger than the male, and also 

 very different in form. It is incapable of moving outside the 

 galleries which it inhabits, partly because it is encumbered by the 

 large eggs which it carries in its body, and partly because it cannot 

 touch the ground with its feet. These (which are extremely short) 

 present an epimeron, a coxa, and leg formed of three joints, the 

 terminal joint being a sort of quadridentate clasper, probably homo- 

 logous with the two joints wldch are distinct in D. mutans, and 

 whir-h M. Robin calls tibia and tarsus. 



The males are smaller and much more active, and also less nume- 

 rous, than the females. Their body is contracted in front and 

 behind ; their legs are much longer than those of the females, and 

 differentl)'^ constructed ; in particular, they bear long hairs, and 

 each of them has a sucker with a long pedicle on its terminal 

 joint. 



M, Ehlers was unable to ascertain whether this Acarian is ovi- 

 parous or viviparous. He supposes that the membrane of the egg 

 becomes much attenuated at the close of the development, and that 

 the embryo is born after having got free from it, or that this membrane 

 is ruptured during the birth. 



In the first period of their life the young Acarians run easily by 

 means of their three pairs of legs, which are long and very like those 

 of the adult males ; each of them boars at its extremity a sucker 

 with a long pedicle, and five hairs, the longest of which exceeds the 

 sucker. 



The transformations through which the animal afterwards passes 

 are the results of a certain number of moults, which must be 

 regarded as being more than mere changes of skin. During these 

 moults the mite remains in a state of immobility and rigidity, which 

 seems to indicate that we have to do with a true case of nymphosis, 

 accompanied by new formations analogous to those o1>served by 

 Weissman in the metamorphoses of insects. Kiichenmeister had 

 previously witnessed phenomena of this kind in Sarcoptes scahiei, and 

 Claparede has described in detail the manner in which a new deve- 

 lopment takes place in the interior of the old skin in Ata.v and 

 HoplopJiora. Matters appear to go on in an analogous fashion 

 in the species observed by M. Ehlers, although this naturalist 

 was unable to ascertain positively that complete histolysis takes 

 place. 



