Gr. H. F. Nuttall 
151 
mostly springs open on the ventral side of the egg, hinging on the dorsal 
side (Fig. 9, 9 and Fig. 10), but it may spring laterally or dorsally, 
or be completely knocked off (Fig. 9, 10 - 13 ). There is therefore no 
constancy about the manner in which the operculum springs 1 . 
Fig. 10. Pediculus humanus (corporis). The larva in the act of issuing from an egg 
attached to a hair. The right-hand figure shows the ventral aspect of the same 
larva, sketched a few moments later, the hair being intentionally omitted. From 
sketches of the living insect. 
1 This appears from counts made on eggs to which the opercula still adhered: of 100 
corporis eggs laid on cloth, the operculum had opened ventrally in 70, laterally in 27 and 
dorsally in 3; similar eggs laid on hair gave the figures 69, 21 and 10 respectively. Of 100 
capitis eggs laid on hair, the operculum had opened ventrally in 43, laterally in 37 and 
dorsally in 20. The number of pores in the operculum is inconstant as shown in the 
figures. 
