4RT. 20. STUDIES OF THE BITING LICE EWING. 



elapsing device again consists of the modified last two pairs of legs, 

 but the modification is entirely different from that in Gyrofus. The 

 last two pairs of legs have their tibiae and femora curved and 

 transversely striated, and by means of the legs on one side opposing 

 those on the other side, individuals were observed to clasp the larger 

 hairs of their host. When small hairs are clasped the tibia itself 

 functions as a large claw and holds the hair tightly by means of 

 pressure against the femur. By observing individuals under the 

 binoculars they could be seen to move rapidly either up or down a 

 hair, and with some hesitancy from one hair to another. G. ovalis, 

 on the other hand, works itself with ease across the hairs of its 

 host. With G. porcelli locomotion takes place either forward or 

 backward, and with almost equal facility, but not sideways. They 

 can crawl either way on a smooth glass surface. This species has so 

 adapted itself to resting and crawling on a single hair that we 





Fig 1 — Monogyropus longus. Leg II showing tarsus locked in the furrowed 



CROTCH of FBMORAr. TENACULUM. DOTTED LINES SHOW POSITION OF LEG WHEN EX- 



TENDED. 



observe not only its remarkable slimness of body but also a median 

 groove, " hair furrow," on the ventral side of the abdomen. 



Response to temperature.— C\i^s of hairs infested with G. porcelli 

 were taken and placed in watch glasses. In a few minutes the lice 

 became restless and in less than an hour all had left the hair tufts. 

 Wlien these wandering individuals were placed again on the guinea 

 pig they immediately, without exception, scrambled between the hairs 

 and went down next to the skin of the host. Was this a response 

 to the animal heat of the host? 



The fact that the lice on the guinea pig remain so constantly next 

 to or near the skin indicates again that the warmth of the body at- 

 tracts them, yet we are not warranted in concluding that this is the 

 case without a demonstration under experimentally controlled condi- 

 tions. 



Mating.— K broad individual which was taken to be a specimen of 

 Gyropus ovalis was observed on a guinea pig and removed with a 

 559&— 24— Proc.N.M.vol.63 36 



