FROGS. 23 



(PI, V, fig. 1), marshy expanses of other types, grassy overflows 

 (PI. VII, fig. 1), and shallow, dead streams. In other situations than 

 these it breeds sparingly. In some places it begins la^ang before 

 April 1, and the period of ovulation may extend to May 15. In 

 general, when the air temperature reaches 43 to 48°, and certainly 

 when it averages 51 to 55°, the leopard frog begms spawning. The 

 temperature oi the water varies from 43 to 45° at the beginning of 

 breeding to 50 to 65° at its crest. The leopard frog may lay at any 

 time of day, even at noon, but more frequently it spawns at night. 

 Leopard frogs have a tendency to congregate in large numbers and 

 often 40 or more bunches of eggs are recorded witliin small circum- 

 scribed areas (PI. XIII, fig. 2). At such times, when an area is ap- 

 proached, the mated pairs often seek cover under the bunches which 

 have already been laid. 



The egg masses of the leopard frog may be attached to submerged 

 cat-tails, twigs, sticks, grass, etc., or as ohen may rest on the bottom 

 unattached. Several times the water's surface has been observed to 

 be so ]ow that the tops of the bunches appeared at the surface. The 

 bmiches of eggs occur in the open, unprotected, marshy expanses, 

 or in overflows where the edges and bottoms have plenty or grass. 

 One will often find the egg masses interspersed with algae and dead 

 leaves, which so fill the shallows that the bottom can not be seen. 

 As a rule, the leopard frog tends to seek shallower water and more 

 swampy localities than the \jood frog. The egg mass at ovulation 

 is 1 or 2 inches in diameter. After it has expanded it is plinthlike 

 or flat, the ^eater diameter varying from 3 to G inches, the smaller 

 from 2 to 3 mches (PI. XIV, fig. 2). The eggs of this species might 

 be confused with those of the wood frog, which lays during the same 

 period. The differences between the two are elaborated under the 

 wood frog (p. 28). Under normal field conditions the eggs hatch in 

 from 13 to 20 days. 



The southern leopard frog, as well as the northern leopard frog, 

 breeds normally in the spring, and hence is called the "spring frog," 

 but occasionally its breeding period may extend until July 4, or 

 later, after tlie fu-st eggs of the species are hatched and the tadpoles 

 transformed. 



The egg mass of the southern leopard frog is plinthlike (PI. XVIII, 

 fi^. 2), and the individual eggs are nardly distinguishable from those 

 of the northern form. These masses may occur attached to vegeta- 

 tion along the quiet side shallows of streams or unattached upon 

 the bottoms of pools, or they may be laid in swampy situations. 



The pickerel frog, as far as the recorded situations show, seeks 

 clear water, and, in the main, is usually found in the upper stretches 

 of our clear streams. It frequents ponds heavily laden with dead 

 leaves of quiet backwaters (Pi. V, fig. 2). The eg";s are frequently 

 found in the shallows of mill ponds, rocky holes of ravines, or low- 

 land pools of wide, meandering streams. The bulk of egg laying 

 occurs during the last week in April and the first week of May. 

 Usually the period extends from April 23 to Ma}^ 15. One may 

 expect this species to begin laying when the temperature of tiie air 

 reaches 50 to 61° and m(jst certainly when 65 to 69° are recorded, 

 provided the temperature of the water is 51 to 64°. 



The eggs of the pickerel frog are almost invariably submerged 

 and attached to sticKS, twigs, or tufts of grass stems. The species 



