92 PROCEEDINGS OF THE NATIONAL MUSEUM. vol. xxviii. 



The genus F(dcidif< r (formerh' Falcnjei) has but few .species, l)ut 

 one of them, F. y^odiuituH Buchholz, presents-several interesting- points. 

 The adult stage differs but little from the normal bird-mite, except 

 that thei-e are two forms of the male — one Avhich has considerable 

 resemblance to the female and the other which has several secondary 

 sexual characters, the anterior paij-s of legs being long and heavy and 

 the immovable finger of the mandibles being greatly enlarged and. 

 lengthened. There is, however, an hypopial stage in the life of this 

 mite which has been the theme of much discussion among acarologists 

 for many years. This hypopial form was described in ISGl by Filippi 

 as HypodecteH and 1)V Mitzsch as Ilypoderas. Uypodrctt.^ is found in 

 various parts of the internal anatomy of birds, generally in the areolar 



Fi(i. 17(i.— Me(;ninia ai.p.ida (after pjg. 177.— Pteronyssus tyrrelli (after 



Tyrrell). Haller). 



and peritracheal tissues. It is of an elongate form, rounded in front 

 and behind, and with eight short legs, two pairs in front and two 

 other pairs toward the posterior end. There are no mouth-organs, 

 and Slosarsky, who examined the anatomy, found no internal struc- 

 tures save a few muscles attached to the legs. From this it was evi- 

 dent that Ilypodectes was a nymph in the state of histolysis. Megnin 

 soon made a more extended stud}-, and found that the mite was a 

 stage in the life-history of a Pterollchus (now placed in the genus Fal- 

 eidJfei). Megnin considers that w^hen the FacuUfcr finds it is being- 

 deprived of shelter and food, by the birds pulling out their feathers, 

 certain normal nymphs transform into the hypopial IlypodtcUs. This 

 then crawls into the respiratory organs, or into the hair-follicles, bur- 

 rows some distance, and there remains until normal conditions are 



