APHANIPTERA. 



23 



Between the twelfth and fourteenth days the larvas may spin them- 

 selves a small silken cocoon, which lies in and is covered by the 

 dust. Not all spin this silken cocoon ; some pupiate into naked, 

 immobile nymphs, which gradually assume a darker colour, and 

 approach the appearance of the imago. About the seventeenth day 

 of pupal life the imago emerges, and very soon commences its rapid 

 hopping movements and voracious habits. 



All the larva; do not pupiate at the same time. Some live through 

 the winter and hatch in the spring. 



Fig. 2. — Pupa of Fulex irritans (greatly enlarged). 



Classification. 



Verrall, in his list of British Diptera, 1888, includes the "fleas" 

 in the Nematocera, and thus does away with the old sub-order, 

 Aphaniptera. The family Pulicida is divided into three genera, and 

 numbers thirteen species in all, viz. : 



Fam. PulicidcB. 

 Genus 1. Pulex, L. 



Irritans, L. 



Fasciatus, Bosc. 



Gallinse, Bouche. 



Melis, Wlk. 



Sciurorum, Bouche. 



Canis, Duges. 



Erinacei, Bouche. 



Goniocephalus, Tasch. 

 Genus 2. Hystrichopsylla, Tasch. 



Obtusiceps, Rits. 

 Genus 3. Typhlopsylla, Tasch 



Octactenus, Kolen. 



Hexactenus, Kolen. 



Musculi, Duges. 



Gracilis, Tasch. 



