Sense organs, [49]

Sexual differences, [23], [51]

Sexual organs, [51]

Simond, [87]

Siphonaptera, description of Order, [108]

Size of fleas, [22]

Species, number of, [4]

Spilopsyllus cuniculi, [77]

Spines 23, [25]

Stephanocircus, [27]