Fig. 7:11. Front legs of males, o, Buenoa uhleri Truxal; 

 b, B. scimitra Bare; c, 6. morganfacea Bueno; d, B. omani 

 Truxal (Truxal, 1953). 



— Middle trochanter produced into a long, spinose process; 



northern California and Mono County 



spinosa Hungerford 1930 



Key to Males of Buenoa 



1. Synthlipsis narrow, less than 1/2 the anterior width of 

 vertex; fore femur with long, conspicuous, sword-shaped 

 stridulatory area consisting of about 60 extremely fine, 

 sclerotized ridges (figs. 7:106; 7:116); widespread in the 

 southern United States scimitra Bare 1925 



- Synthlipsis wide, 1/2 or more the anterior width of 

 vertex, fore femur with smaller stridulatory area con- 

 sisting of less than 25 sclerotized ridges 2 



2. Fore femur with only 4 sclerotized ridges in stridulatory 

 area (fig. 7: lid); southern California and Mexico 



omani Truxal 1953 



- Fore femur with 15 to 25 sclerotized ridges in stridula- 

 tory area 3 



3. Rostral prong longer than 3rd rostral segment, fore 

 femur with 19-24 sclerotized ridges in stridulatory area 

 (fig. 7:11a); southern California, Texas, and Mexico 



uhleri Truxal 1953 



- Rostral prong subequal to 3rd rostral segment; fore 

 femur with 15-18 sclerotized ridges (fig. 7:11c); widely 

 distributed margaritacea Bueno 1908 



REFERENCES 



BARE, C. O. 



1928. Haemoglobin cells and other studies of the genus 

 Buenoa. Univ. Kansas Sci. Bull., 18:265-349, 14 pis. 

 HUNGERFORD, H. B. 



1922. Oxyhaemoglobin present in backswimmer, Buenoa 

 margaritacea. Canad. Ent., 54:263. 



has a long slender clasper. Typical unifasciata is Mexican but 

 specimens identified by R. I. Sailer have recently been collected 

 on Santa Catalina Island by Lee, Ryckman, and Christianson 

 (1955). 



199 



Usinger: Hemiptera 



1924. Stridulation of Buenoa limnocastoris Hungerford 

 and systematic notes on the Buenoa of the Douglas 

 Lake region of Michigan, with the description of ;t new 

 form. Ann. Ent. Soc. Amer., 17:223-227. 

 1933. The genus Notonecta of the world. Univ. Kansas 

 Sci. Bull., 21:5-195, 17 pis. 

 LEE R. D., R. E. RYCKMAN, and C. P. CHRISTIANSON 

 1955. A note on several species of aquatic Hemiptera 

 from Santa Catalina Island, California. Bull. So. Calif. 

 Acad. Sci., 54:20-21. 

 PIERCE, W. D. 



1948. Fossil arthropods of California. 15. Some Hemip- 

 tera from the McKittrick asphalt field. Bull. So. Calif. 

 Acad. Sci., 47:21-33. 

 RICE, L. A. 



1954. Observations on the biology of ten notonectoid 

 species found in the Douglas Lake, Michigan, region. 

 Amer. Midi. Nat., 51:105-132, 3 pis. 

 TRUXAL, F. S. 



1953. A revision of the genus Buenoa. Univ. Kansas 

 Sci. Bull., 35:1351-1523, 17 pis. 

 WALTON, G. A. 



1935. Field experiments on the flight of Notonecta macu- 

 lata Fabr. Trans. Soc. Brit. Ent., 2:137-143. 



Family NAUCORIDAE 



Creeping Water Bugs 



Naucorids are among the least known but widely 

 distributed groups of aquatic Hemiptera. In size, 

 body form, and in their role in the aquatic community, 

 they are comparable to" the Dytiscidae among the 

 beetles. Although fiercely predaceous, they are quite 

 defenseless when molting and fall easy prey to dam- 

 selfly nymphs and other predators at this time. 



Relationships. — Among the Cryptocerata the nau- 

 corids are perhaps closest in structure to the back- 

 swimming Notonectidae and more particularly to an 

 obscure group of Notonectoidea known only from 

 tropical waters, that is, the Helotrephidae. In general, 

 the naucorids are characterized by their oval form, 

 subflattened body, raptorial front legs, and middle 

 and hind legs modified for swimming. 



Respiration. — Most naucorids breathe through the 

 cuticle as nymphs and through spiracles in contact 

 with the air bubble as adults. Adults break the surface 

 film with the tip of the abdomen to replenish the air 

 in their subelytral air space and in the air bubble 

 which appears as a silvery sheen on the pubescent 

 venter. When at rest, naucorids "row" with their hind 

 legs, thus maintaining a current of fresh water over 

 the surface of the bubble. 



A few naucorids, Aphelo cheirus of the Old World 

 and Cryphocricos of the New World, are dimorphic 

 and lack conspicuous pubescence on the venter. 

 The common form in each of the above genera is 

 brachypterous, and thus lacks the subelytral air 

 store. Thorpe (1950) has studied the special problems 

 of respiration and orientation encountered in Aphelo- 

 cheirus. The spiracles open as small tubular "ro- 

 settes" and the lumen of the rosette tubes and the 

 entire surface of the body are covered with an ultra- 

 microscopic hair pile. By means of the electron 

 microscope it was determined that there are approxi- 

 mately 2 million hairs per square millimeter. This 



