148 POND COMMUNITIES 
caddis-worms (Phryganeidae: Neuronia) (Fig. 99), which are also abun- 
dant in the later stages of dense vegetation. This worm’s case is some- 
what similar in form to that of Leptoceridae, being a circular tube, but it 
is made of pieces of grass blades or other pieces of plant fragments instead 
of sand grains. The pieces are fastened together with silk. The worm is 
found creeping among the vegetation, drawing its case after it. Ammnicola 
(Fig. 100), the river-dwelling snail, is common, especially on twigs and 
logs. In the mature stage represented by Pond 14 (Fig. ror) the com-. 
mon newt (Fig. 102) probably reaches its maximum abundance. The 
snails which are at best advantage in these ponds are the lung breathers. 
They can here come to the surface for air, and food is abundant, as the 
surfaces of the plants are covered with algae and these form the food of 
the snails. Those snails which come to the surface for air are common. 
Planorbis campanulatus (Fig. 103) is characteristic of the mature stage 
and Lymnaea reflexa (Fig. 104) in the older stages. The individuals in 
this case are larger than those of the temporary marshes (cf. Figs. 104 
and 125, pp. 149,175). Planorbis parvus (Fig. 105) is commonest in the 
earliest phases and Planorbis hirsutus (Fig. 106) in the later. Diving 
beetles (Fig. 107), which are common throughout, are most numerous 
in the denser vegetation. The soldier-fly larvae (Fig. 108) are often 
common in the dense filamentous algae of the mature phases of the asso- 
ciation; here the number of all dipterous larvae is greater than at any 
other point. Midge larvae occur in great numbers, having their cases 
among the algae. Horseflies (Fig. 92), also Tanypus, Ceratopogon, and 
some mosquitoes are present. Specific identification, however, is not 
possible, and whether or not the species differ in modes of life or reactions 
from those inhabiting the earlier stages in the pond series has not been 
determined. 
Adult aquatic insects have increased with the increase in vegetation, 
in a remarkable fashion. ‘The prominent forms are the larger bugs, such 
as the electric-light bugs (Zaitha fluminea and Belostoma americana 
Leidy, with Benacus griseus Say). The water-boatmen are also common. 
The species of these are not well known, and we cannot say whether or 
not they are the same in the older and younger ponds. Back-swimmers 
are also abundant (Notonecta variabilis and undulata, Buenoa platycnemis, 
and the small form, Plea striola, occur here). They are few in number 
or absent from the younger ponds. 
Some animals particularly abundant in the older stage are the 
common leech (Placobdella parasitica) (Fig. 109), the larvae of a netted- 
winged insect (Chauliodes rastricornis) (Figs. 110, 111), the large flat 
