Fig. 13:2. Larvae of Amphizoa leconiei. a, dorsal aspect; 

 b, ventral (Hubbard, 1892). 



of Amphizoa gave "the impression of a terrestrial 

 bettle with amphibious or semiaquatic habits." 

 Edwards (1951) suggested that the bristles and long 

 silky hairs along the inner edge of the tibiae are 

 vestiges of former swimming hairs, and thus implied 

 an ancestry with a more active aquatic life. 



Respiration. — The larvae have the eighth pair of 

 abdominal spiracles very large and close together on 

 the tergite (fig. 13:1c). Edwards (1954) reports that 

 when dislodged and floating in relatively quiet water 

 young larvae assume a characteristic pose, with the 

 abdomen horizontal and the eighth pair of spiracles 

 at the surface of the water, but with the thorax and 

 head tucked under the abdomen so that the mandibles 

 lie beneath the abdominal tip. He found that in captiv- 

 ity the older larvae always climbed up some object 

 till they were above the surface of the water, and 

 stayed there till they reentered it to capture prey. 

 Adults depend on refilling the subelytral chambers 

 at intervals, and carry a bubble of air at the tip of 

 the abdomen when they submerge. 



Life history. — Little was known of amphizoid his- 

 tory until Edwards published his data (1954). He found 

 the surprisingly large eggs (2.1 mm. by 1 mm.) at 

 Glacier Park, Montana, in late August. They were 

 fastened loosely in cracks on the undersurface of a 

 piece of floating, weathered driftwood. Larvae nearly 

 ready to emerge were tightly tucked up in the eggs, but 

 upon removal were found to measure a little more than 

 3.5 mm. in length! 



Very young larvae have been taken in November, 

 and mature larvae, 12 to 15 mm. long, in late June, so 

 they must overwinter in the first or second instars. 



Pupae are still unknown, but Edwards states that 

 H. P. Chandler found two mature larvae, apparently 

 ready to pupate, in protective cases "lodged in 

 debris-filled crevices between logs, one at a distance 

 of about one and a half feet above the water and the 

 other about four feet above the water level and two 



301 

 Leech and Chandler: Coleoptera 



feet back from the edge of the stream." This was al 

 the north fork of the Fresno River, Madera County, 

 elevation 4,000 foot, on Juno 1. 



Adults aro abundant in middle and lato August. 

 Most specimens in collections were taken during the 

 period May to September, inclusive. This is the time 

 when collectors aro in the field, and does not prove 

 that the beetles cannot bo found in other months. 

 Darlington (1929) records freshly emerged adults of 

 A. insolens LoConte at North Bond, Washington, 

 July 30. 



Habitat and distribution. — The American species 

 occur in streams, rivers, and sometimes in lakes, 

 from near sea level to an elevation of at least ten 

 thousand feet. They aro most numerous at elevations 

 between 1,000 and 3,000 feet. 



Adults are often found clinging to water-soaked 

 logs, especially old decaying ones full of cracks and 

 holes, lying well out in the current. With the larva they 

 crawl among stones and gravel at the water's edge, on 

 logs which project out into the water, and particularly 

 on debris washed to the sides of eddies or held by 

 log jams. Darlington records many A. lecontei Mat- 

 thews and a few A. insolens from wind-driven logs 

 and trash floating at the outlet of a lake. Such sta- 

 tions are correlated with their food habits: they were 

 formerly presumed to eat chiefly sluggish or drowned 

 insects. Edwards (1954) found that adults of A. in- 

 solens and A. lecontei showed amazing speed in 

 capturing agile plecopteran nymphs, and would touch 

 no other food; all stages of the larvae also fed only 

 on living stonefly nymphs. 



Dispersal is presumably by flight, but the only 

 record of flight is by Darlington, who knocked an 

 A. lecontei down as it flew over Lake Minnewanka at 

 Banff, Alberta. 



Except for A. davidi Lucas of eastern Tibet, all 

 the described species are American. They occur in 

 the Rocky Mountains and westward almost to sea 

 level, and from Alaska to southern California. The 

 common A. insolens and A. lecontei were described 

 in 1853 and 1872 respectively, A. striata Van Dyke in 

 1927, and A. carinata Edwards in 1951. 



Taxonomic characters. — Three of the four American 

 species have characteristic differences of outline, 

 convexity, and elytral carination, by which they may 

 be recognized at a glance. They show slight structural 

 differences in pronotal widths and lateral crenula- 

 tions, grooving of the outer rear edge of the front 

 tibiae, median lobes of the male genitalia, and valvi- 

 fers and paraprocts of the female genitalia. Males may 

 be distinguished by having a single brush of short 

 hairs on the underside of the first segment of the 

 front and middle tarsi; in females this segment is 

 armed with bristles like those of the following seg- 

 ments. 



Genus Amphizoa LeConte 



Only one species has been reported from California. 

 Elytra evenly convex from side to side (fig. 13:1a); pro- 

 notum at least as broad at middle as at base, with coarse 

 lateral crenulations; groove on outer hind edge of front 



