464 CALIFORNIA ACADEMY OF SCIENCES. 



In the two subfamilies of the Psocidse, the winged 

 Psocinae and the degraded, wingless Atropina?, the atti- 

 tude of the head varies from a hanging or vertical posi- 

 tion in the Psocina? to the nearly horizontal position of 

 Atrofos. With the change from vertical to horizontal 

 position there goes a marked flattening of the head, so 

 that the head of Atroftos (plate lxiv, figs. 5 and 7) in its 

 horizontally projected attitude, its flattened condition, and 

 the limiting of the mouth-parts to the ventral aspect of the 

 head, shows both in its relation to the body of the insect 

 and in its own shape and condition, a great similarity to 

 the horizontal, flattened head of the Mallophaga. The 

 clypeus of Atropos is large, projecting far forward, and, 

 as in the Mallophaga, forms the frontal margin of the 

 head, the labrum lying on the ventral aspect of the head 

 (plate lxiv, fig. 5). All the mouth-parts lie on the ven- 

 tral aspect of the head (plate lxiv, fig. 5) The mandi- 

 bles (plate lxiv, figs. 5, 6, and 8) are strong, toothed, 

 and present distinct protruding condyles wholly similar 

 in position and general character to those of the Mallo- 

 phaga (see plates lx-lxiii). The maxilla? (plate lxiv, fig. 

 5) I do not understand, but there are no conspicuous ter- 

 minal free lobes; there is a large basal part, and artic- 

 ulating with it the conspicuous 4-segmented palpi. The 

 fork is long and slender, projecting farther forward than 

 the front margins of the closed mandibles. The labium 

 (plate lxiv, fig. 5) shows a large elongate submentum, a 

 hexagonal mentum, and a ligula composed of two large, 

 free outer lobes, and a median bilobed part composed of 

 the inner lobes of the two sides partly coalesced. Ac- 

 cording to Burgess what I have called outer lobes are the 

 reduced i-segmented palpi. In addition the oesophageal 

 sclerite (described hereafter for Psocus under the name 

 " oesophageal bone ") shows through the basal part of the 

 labium. 



