207 



Usinger: Hemiptera 



1948. Revision del Genero "Abedus" Stal. Com. Mus. 

 Argent. Cien. Nat. (Zool.). No. 5, pp. 1-24, Tab. I-lll. 

 DIMMOCK, GEORGE 



1886. Belostomidae and some other fish-destroying bugs. 

 Ann. Rpt., Fish and Game Comm., Mass. Pub. Doc. 25 

 (D.), pp. 67-74. 

 'DUFOUR, L. 



1863. Essai Monographique sur les Be'lostomides. Ann. 

 Soc. Ent. France, 3:373-400. 

 1 HARVEY, G. W. 



1907. A ferocious water-bug. Canad. Ent., 39:17-21. 

 HIDALGO, JOSE 



1935. The genus Abedus. Bull. Univ. Kansas, 36:493-519. 

 HUNGERFORD, II. B. 



1920. The biology and ecology of aquatic and semiaquatic 



Hemiptera. Kansas Univ. Sci. Bull., 21:1-328, 30 pis. 



\ 1925. Notes on the giant water bugs. Psyche, 32:88-91, 



3 figs. 

 : KIRKALDY, G. VV. 



1908. In Kirkaldy and Bueno, A catalogue of American 

 aquatic and semiaquatic Hemiptera. Proc. Ent. Soc. 



Wash., 10:173-215. 

 MAYR, G. L. 



1863. Hemipterologische studien. Die Belostomiden. 



Verh. Zool.-Bot. Ges. Wien, 13:339-364, 10 figs. 

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21:399-438. 

 SEVERIN, II. II. P., and II. C. SEVERIN 



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Vol. 1, No. 3, pp. 1-44, 1 pi. 

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Family NEPIDAE 



Water Scorpions 



Members of the family Nepidae are distinguished from 

 all other water bugs by their long, slender, respiratory 

 filaments and by the three pairs of small, oval disc- 

 like "static sense organs" at the sides of the second, 

 third, and fourth visible ventral segments. The anterior 

 legs are raptorial and the remaining legs are slender 

 and thus better suited to progress among tangled mats 

 of vegetation than to swimming in open water. Never- 

 theless, an ungainly Ranatra may be seen occasionally 

 in open water with its legs moving alternately. 



Life history. — The life history of Ranatra has been 

 studied by Torre-Bueno (1906) in the eastern United 

 States. Winter is passed in the adult stage. Egg-laying 

 takes place during the growing season, the eggs being 

 inserted in plant tissue with two slender filaments 

 protruding (fig. 7:20c,d). These filaments are longer 

 than the egg, and the incubation period varies from 

 two weeks to a month. The five nymphal instars each 

 required a week or more according to Torre-Bueno. 



Feeding habits. — Water scorpions are voracious 

 feeders on practically any organism of suitable size 

 in their environment. Small Crustacea, mayfly nymphs, 

 and mosquito larvae have been mentioned, among 

 others. Water scorpions do not pursue their prey, but 

 lie in wait and capture organisms that chance to come 

 close to their place of concealment. Ranatras are 

 especially well concealed by trash or tangled plant 



Fig. 7:19. Ronafro brevicollis Montandon, mole, Walnut Creek, 

 Contra Costa Co., Calif., Aug. 9, 1927 (R. L. Usinger.) 



growth because of their sticklike appearance. Brooke 

 and Proske (1946) showed by precipitin tests that a 

 Ranatra fusca adult had recently fed upon immature 

 mosquitoes. Omerod (1889) records the European R. 

 linearis as attacking small fish. 



Distribution. — Only three genera of water scorpions 

 are known from North America. One of these, Nepa, is 

 strictly eastern, the single species, N. apiculata Uhl., 

 being confined to the eastern states with its nearest 

 ally, N. cinerea Linn., occurring in Europe. Curicta 

 is a Neotropical genus with only two species extend- 

 ing into the southern part of the United States. Ranatra 

 is by far the dominant genus in North America and 

 throughout most of the rest of the world as well. It is 

 the only genus that occurs in California. R. brevicollis 

 Montd. (fig. 7:19) is the commonest California species 

 and is apparently confined to the state. Two additional 

 species can now be recorded, fusca P. B. from Shasta 

 County in northern California and quadridentata Stal 

 from the Colorado River. 



Pierce (1948) described two fossil species, Ranatra 



