INSECTA. 303 
Gyropus Nirzscu. ‘'Tarsi uniunguiculate. Labial palps none. 
Of this genus only few species are known, which live on the Cavie and 
the Sloth (Bradypus tridactylus) 7. e. on American species of Mammalia. 
OrvDER IV. Suctoria s. Siphonaptera. 
Apterous, hexapod, undergoing perfect metamorphosis. Mouth 
suctorial; rostellum formed of two serrated laminz and a single 
more slender seta, included in a bivalve articulate sheath. 
Family VII. Pulicide (characters of the order are those of the 
single family). 
Pulex WU. [Characters of the order.] Body compressed. 
Antennz short, with three or four joints, the last large, flat, 
serrated, recetved in a small cavity and covered with a scale. 
Maxillary palps with four joints, porrect. Posterior feet saltatory. 
Tarsi with five joints. 
The order of sucking Insects, which contains the genus Flea, 
agrees in the complete metamorphosis with the Diptera ; but the 
oral parts have little resemblance. The flea is perfectly distin- 
- guished from the hemipterous sucking Insects not only by the 
perfect metamorphosis, but also by the oral parts, by the presence 
of palps for instance. Ducxs first drew attention to four small round 
plates, which are situated on the last two segments of the thorax, 
and of which the posterior pair is the largest. These plates, which 
in colour and substance do not differ from the rest of the horny 
covering of the body, may be looked on as rudiments of wings. 
The resemblance with the metamorphosis of the Hymenoptera, 
especially in the pupa, together with the presence of these four 
rudimentary wings, may serve to explain in some degree why an 
inclination has prevailed to regard the suctoria as abortive hymen- 
opterous Insects. 
There are two simple eyes, which in Pulex vespertilionis Ducks 
are wanting. The sucker is inclosed by the flat labial palps con- 
sisting of (three?) joints, and is composed of two flat set serrately 
toothed on the edge and ribbed longitudinally in the middle (scalpella 
Krrey and Spence, mandibles), and a thin smooth thread of the 
same length (/igula Sav.) There is no upper lip present, unless it be 
