6 
Psyche 
[ March 
termed flexor membranes. Crampton (1923) suggests two 
possible derivations for the pulvilli: either they arose as 
portions of a divided arolium (see condition in Hymenop- 
tera, Fig. 26, Plecoptera, Fig. 7, and Mantispa, Fig. 19.) 
or they are detached membranous areas from the under 
side of the claws (see condition in some Ephemeroptera, 
Fig. 2, Homoptera and Hemiptera, Figs. 14 and 15, and the 
relation of basipulvilli to such membranous areas in Blat- 
tids.) 
Ungues . — The claws.. 
Unguifer . — (tubercula, and Gelenkhocker of de Meijere) 
refers to a small dorsal sclerite by which the claws are ar- 
ticulated with the distitarsus. 
Unguitr actor — (tarsulus, calcanea). This sclerite is 
the most constant structure of the pretarsus and is easily 
identified in all insects thus far observed because its gen- 
eral appearance is always the same though varying in size 
and shape. The surface of the unguitractor is sculptured 
to a greater or less degree with nodules which are some- 
times almost spinelike. These nodules appear to corres- 
pond with the polygonal cells of the hypodermis and these 
cells may be seen through the chitin with high magnifica- 
tion. Snodgrass (1927) shows that in Tibicen this plate 
may be divided into two sclerites and also he figures in the 
membrane distal to the unguitractor, two small plates which 
he says may represent the arolium. It seems more likely 
that they are a divided planta but there is little evidence as 
yet for either supposition. 
Discussion. 
Order Odonata 
Anax junius Drury. (Fig. 1) 
The claw-segment of Anax is simple and consists of the 
unguitractor plate (ut) with the expanded distal portion 
which is probably an empodium (em?) and of the lateral 
fleshy pads, flexor membranes (fm.), — which transmit 
tension to the ventral surfaces of the claws. The Gleit- 
flache of de Meijere, or thickened ventral portion of the 
