140 
Biology of Pediculus humanus 
The result was striking. During the first 24 hours, although replaced 
three times upon the platform, she laid 6 eggs in succession, at one 
spot midway along the under margin of the cloth, at X, along the side 
a — d. In the second 24 hours she laid 7 more eggs at spot X, the 
area dotted with eggs being about 0-5 cm. across; 2 eggs were laid 
apart close under the edge of the cloth along the side d —c, and 1 was 
laid near the diddle of the upper surface B. The cloth was now reversed, 
the rough side B being undermost, whereby the eggs at X■ appeared 
uppermost. In the third 24 hours, one more egg was laid at X (making 
a total there of 14), 4 were laid on the (now) under surface of the 
cloth B along margin c— d in an area denoted by Y. In the fourth 
24 hours 7 more eggs were laid at Y and 1 was laid on surface A 
near c. 
Expt. 1 (continued ). The female having been removed from the 
cloth, the latter, with only the eggs upon it, was returned to the ther¬ 
mostat for two days. Beginning on 26. in. 17, the rough side (B) of 
the cloth being uppermost, another female was placed on the platform; 
during the following 24 hours she laid 1 egg at X and 1 egg at Y. A 
third female was now placed on the platform and during the following 
24 hours she laid 6 eggs at X (underside) and 1 near the platform on 
the upper surface B. 
At the end of the experiment, out of a total of 38 eggs, 21 had been 
laid at X, and 12 at Y along margin c— d, 3 along margin d—c on the 
surface opposite to Y, and only 2 were scattered elsewhere. 
It is certain, therefore, as Bacot indicated, that corporis females 
show a marked tendency to return and oviposit on the same spot where 
eggs have been laid by themselves. My experiment shows, that a 
female will select a spot previously chosen by another female, and 
the reversal of the cloth showed that the tendency to creep beneath 
a cloth to lay to a great extent overcomes the tendency to return to 
the same spot if the spot is put uppermost. 
B. Capitis. 
Bacot (loc. cit.) states that the “homing instinct” with regard to 
oviposition is less marked in capitis than in corporis. I have subjected 
the statement to the test of enumeration in two comparative experiments. 
I. (a) Some capitis laid 114 eggs on a hair-frame; nearly all were 
aggregated in two areas at one side and at one end of the frame, 71 
eggs being laid on 4 adjoining parallel hairs alone. ( b ) In a parallel 
experiment with corporis, 95 eggs were laid, mostly in one area, 81 
