north to British Columbia, east to Wyoming 



robertsi Zimmormann 1924 



— More elongate species, ovate; basal pronotal plicae 

 more than 1/4 of length as measured above; elytra with 

 a common postmedian sutural blotch, and each usually 

 with 1 to 3 additional small blackish marks in apical 

 half; Humboldt and Lassen counties, north to British 

 Columbia dorsomaculatus Zimmermann 1924 



3. Prosternal process plainly, usually broadly, margined 

 at s ides 4 



— Prosternal process not at all margined at sides, or 

 at most feebly so near apex 6 



4. Mid-metasternum with a large fovea on each side of 

 middle, just behind an imaginary line joining posterior 

 margins of hind coxae; prosternal process almost 

 parallel-sided; San Diego, San Bernardino, Santa 



Barbara, and San Mateo counties 



concolor LeConte 1852 s 



— Mid-metasternum without a large fovea on each side 

 of middle, though often with a longitudinal impression; 

 elytra almost unicolorous 5 



5. Punctures of first 5 rows of elytral striae confused 

 and confluent, those of 6th to 10th distinctly separated; 

 fine punctures of elytral interspaces numerous, crowded 

 and mixed up with those of the striae; "California"; 

 Baja California at U.S. boundary 



rugosus Roberts 1913 



— Punctures of all elytral striae clearly separated, not 

 confused or confluent; each elytral interval with a 

 row of small deep punctures, sutural row irregularly 

 double, other rows single with some irregularities, 

 not mixed with strial punctures except along basal 



margin; San Diego County 



mimeticus Matheson 1912 



6. Central part of prosternum, anterior to coxae, sharp- 

 ly margined laterally and distinguishable from the 

 side parts; metasternum between middle coxae on 

 slightly different plane from part behind coxae, with 

 a central fovea in declivity 7 



— Central part not margined laterally, merging into side 

 parts; mid-metasternum on a plane between and behind 

 middle coxae 8 



7. Delimiting lines of central part of prosternum extending 

 to anterior margin; Tulare County, Mariposa County 



cylindricus Roberts 19 13 



— Delimiting lines disappearing halfway between coxae 

 and front margin of prosternum; Monterey County north 

 to Oregon gracilis Roberts 1913 



8. Subsutural row of interstitial punctures with at least 

 an occasional misplaced puncture, and usually more 

 or less double anteriorly; strial punctures large; 

 British Columbia to Oregon, Utah; California 



leechi Wallis 1933 



— Subsutural row of interstitial punctures regular and 

 rather sparsely placed basally; strial punctures smaller 

 and of almost uniform size; California to British 

 Columbia to Massachusetts 



subguttatus Roberts 1913 



Genus Apterallplus Chandler 



A tiny (1.5 - 2.5 mm.) spindle-shaped, humpbacked species; 

 wings reduced to little pads, nonfunctional; San Mateo 

 County; Stanford University campus, Santa Clara County 

 parvulus (Roberts) 1913 



REFERENCES 



BALFOUR-BROWNE, F. 



1940. British water beetles. Vol. 1- London: Ray Soc, 

 xx+375 pp., 89 text figs., 5 pis., 72 maps. 



H. tumidus LeConte 1880, a Texas species, has been recorded 

 from "California" but presumably on the basis of mislabeled 

 specimens. It would run to concolor in the key, but the humeral 

 umbone area is asperate, not smooth between the usual punctures. 



305 

 Leech and Chandler: Coleoptera 



CHANDLER, H. P. 



1943. A new genus of Ilaliplidae (Coleoptera) fl 

 California. Pan-Pac. Ent., 19:164-158, 7 toxt figs. 

 GUIGNOT, F. 



1947. Coleopteres Hydrocanthares. In Faune <1<- Franco, 

 48:1-288, 128 text figs. 

 HATCH, M. II. 



1953. The beetles of the Pacific Northwest. Hart I: 

 Introduction and Adephaga. Univ. Wash. I'ubl. Biol., 

 16:vii+ 1-340 incl. front., 2 text figs., 37 pis. 



HICKMAN, J. R. 



1930. Life-histories of Michigan Ilaliplidae (Coleoptera). 



Pap. Mich. Acad. Sci., 11:399-424, pis. XLVII-LV. 

 1931a. Respiration of the Ilaliplidae (Coleoptera). 

 Pap. Mich. Acad. Sci., 13:277-289, 4 text figs., 1 

 table. 

 19316. Contribution to the biology of the Ilaliplidae 

 (Coleoptera). Ann. Ent. Soc. Amer., 21:129-142. 

 MATHESON, R. 



1912. The Ilaliplidae of America north of Mexico. Jour. 

 N.Y. Ent. Soc, 20:156-193, pis. 10-15. 



ROBERTS, C. II . 



1913. Critical notes on the species of Ilaliplidae of 

 America north of Mexico with descriptions of new 

 species. Jour. N.Y. Ent. Soc, 21:91-123. 



SPANGLER, P. J. 



1954. A new species of water beetle from Michigan 

 (Coleoptera: Ilaliplidae). Ent. News, 65:113-117, 

 4 figs. 



WALLIS, J. B. 



1933. Revision of the North American species (north 

 of Mexico) of the genus Haliplus, Latreille. Trans. 

 Roy. Canad. Inst., 19:1-76, 38 text figs. 

 WILSON, C. B. 



1923. Water beetles in relation to pondfish culture, with 

 life histories of those found in fishponds at Fairport, 

 Iowa. Bull. Bur. Fish., 39:231-345, 148 figs. 

 YOUNG, F. N. 



1954. The water beetles of Florida. Univ. Florida Stud., 

 Biol. Sci. Ser. 5:lX+238 pp., 31 figs. 



Family DYTISCIDAE 



Predaceous Water Beetles 



Dytiscids are widespread, numerous in species, lo- 

 cally common, active during the day, and sometimes 

 countless numbers are attracted to lights at night. 

 Except for the Gyrinidae, they are more readily seen 

 than other aquatics, and most people who refer cas- 

 ually to "water beetles" have them in mind. 



The adults spend most of their time under water, 

 but must obtain air either by breaking through the 

 surface film or from bubbles attached to aquatic 

 plants. Their hind legs are used like oars, and in 

 articulation, form, and vestiture are specially adapted 

 for swimming. Eggs are laid in wet places just out of 

 the water, or more commonly on or in plants under 

 water. The larvae, like the adults, are predaceous; 

 those of most genera must come to the surface to 

 obtain fresh air. When mature they leave the water to 

 form pupal cells in the damp soil or sand nearby. 



Relationships.— With the hind coxae fused to the 

 metathorax and completely dividing the first visible 

 abdominal sternite, the Dytiscidae, with related 

 families of aquatic habits (Amphizoidae, Ilaliplidae, 

 Ilygrobiidae, Noteridae, Gyrinidae), form the section 

 Hydradephags of the superfamily Caraboidea, sub- 

 order Adephaga. The terrestrial families (Cicindelidae, 

 Carabidae) form the section Geodephaga. The aquatic 



