5 1 6 
Psyche 
[September-December 
The thoracic plastral hairs of A phelocheirus are approximately 
5-6 /x m in length, as Thorpe (1950) also noted. They are thus 
somewhat shorter than those of Cryphocricos , but appear to be com- 
parable to the latter in diameter. Their bases are somewhat thicker 
(approximately 0.4 /xm) than their tips (approximately 0.3-0.35 /xm). 
In both genera adjacent hairs seem to l ; e very clcse to each other. 
The nodules may help to hold them apart, allowing room for air to 
circulate between them. Also, because of the thickness of the gold 
coating (0.02-0.04 /xm), the hairs probably appear, under the scan- 
ning electron microscope, somewhat thicker, and the intervening 
spaces smaller, than they actually are. By means of the light and 
transmission electron microscopes, Thorpe and Crisp (1947a) esti- 
mated the space between adjacent hairs on the abdominal sternites of 
A phelocheirus to be approximately twice as great (0.4 /xm) as the 
diameter of the tip of a single hair (0.18-0.25 /xm). The discrepancy 
between their observations and ours may be due, in part, to the dif- 
ferent techniques employed. It is also possible that the hairs are less 
densely packed on the abdominal sternites than on the thorax of 
A phelocheirus. 
The hairs of both Cryphocricos and A phelocheirus are much 
shorter, narrower, and more densely packed than those which cover 
the ventral surface of the abdomen of Pelocoris fernoratus , a “slow- 
water” naucorid with air-bubble respiration (Parsons 1974). A brief 
observation of one specimen of Pelocoris revealed that the hairs on 
the second abdominal paratergite lack basal nodules and are 30-40 
/xm long, 2-3 /xm wide at the base, and approximately 10 /xm apart. 
(2) Leaf -like Setae 
Leaf-like setae occur on the ventral paratergites of the abdomen 
(Fig. 1, light stippling lateral to LS). They extend all the way to 
the lateral edge of the body on the second abdominal paratergite, and 
nearly to the lateral edge on the more posterior paratergites. On the 
second paratergite (PT 2) a narrow anteromedial strip adjoining 
the metathoracic episternum (ES III) and the metacoxal indentation 
(MCI) lacks leaf-like setae (Fig. 6). This “nonfoliated” region is 
larger in Cryphocricos hungerfordi than in C. barozzii. The second 
abdominal spiracle (Fig. 1, SP 2) and sense organ (SO 2), like 
those of the other abdominal segments, lie in the “foliated” region. 
In C. barozzii the flattened setae are widest (8-20 /xm) near their 
bases and are 20-40 /xm long. In C. hungerfordi a smaller insect, 
they are approximately 75% this size. They appear to be socketed 
(Fig. 8) and are arranged somewhat like shingles, in closely packed, 
