Mar., 1904.] Clasping Organs in the Pediculidae. 107 



NOTE ON MORPHOLOGY OF CERTAIN CLASPING 

 ORGANS IN THE PEDICULIDAE. 



Herbert Osborn. 



The results of Parasitism in developing special organs for 

 adherence possess a prominent Morphological interest since these 

 organs exhibit a high degree of specialization which contrasts 

 markedly with the degeneration of other sets of organs. The 

 Pediculidae present a number of instances of such structures which 

 seem not to have been described in detail and the purpose of this 

 note is to call attention to some of them. 



In Haematopinus urius there is a protractile disk at the distal 

 end of the tibiae, the purpose of which, as suggested in an earlier 

 note, being to press against the hair in opposition to the tarsal 

 claw and thus assist in the hold upon the hair. In the previous 

 description of this structure no attempt was made to explain the 

 apparatus or its movements, but it was mentioned that the disk 

 played back and forth in a pit-like depression of the tibiae, and 

 the examination of balsam mounts of this organ fails to show very 

 clearly the basis of movement. There is a large muscle running 

 through the tibia and forking near the middle of the tibial joint, 

 one part going to the tibial spur, the other passing on to the tarsal 

 joint while from the latter a fiber runs to the base of the protrac- 

 tile disk. This would seem able to retract the organ and com- 

 bined with an elastic frame- work for the protraction would account 

 for the movements. I have been entirely unable to discover any 

 muscle strands which would seem to act for the protraction and 

 beHeve that this may be provided for in the movements of the 

 chitinous wall assisted partiall}' by the flexion of the tarsal joint. 

 The figure shows the distribution of the muscle strands as noted 

 in the majority of specimens examined. 



In Haematopinus macrocephalus there is a disk-like organ in 

 the same position as in the preceding species, but it differs from 

 the protractile disk in urius in having a convex surface, appar- 

 ently membranous, and within the bulb of the organ maj^ be seen 

 a half dozen strands of muscles, the contraction of which would 

 serve to withdraw the surface membrane. The muscle strand 

 runs from the base of the tibiae to the cup-like depression of the 

 disk, but not having examined this organ ni living specimens the 

 extent of the protraction, if any, is unknown. The musculature 

 of the tibial joint is shown in the accompanyiug figure. 



In Euhaematopinus abnormis the posterior pair of legs is very 

 greatly modified, so much so that they cannot serve any function 

 as ordinary organs of locomotion, but must be adapted purel}- for 

 clasping, the femur and tibia each possessing expanded disks, the 

 former upon the anterior part of the femur and so arranged that 



