TAMARACK FOREST COMMUNITIES 195 
Ground stratum: On the sphagnum, which sometimes occurs in the 
pools, various insects and spiders occur, including, according to Hancock 
(40), two species of sphagnum crickets. On the higher ground numbers 
of typical moist forest animals occur sparingly. Frogs are often numer- 
ous. The common frogs (Rana pipiens and clamata) and the marsh 
tree-frog (Chorophilus nigritus) occur in summer. The wood-frog and 
Pickering’s tree-frog (Rana sylvatica and Hyla pickeringii, Fig. 150) are 
regular residents; probably both breed in the pools (139) between the 
hummocks. Farther north the hermit thrush nests on the hummocks 
amid the dense undergrowth. This is also the typical haunt of the 
varying hare (Lepus americanus Erx.) (83, 142, 143), which is white in 
winter and brown in summer; it is common in tamarack swamps farther 
north. The lynx (p. 15) was probably once common near Chicago and 
is most likely to have frequented these swamps. Adams (83, 42) records 
its tracks on the hummocks of the tamarack swamps on Isle Royale in 
Lake Superior. Judged by its tracks it wanders far. It feeds largely 
on hares, the numbers of which fluctuate (inversely) with the numbers of 
lynx. The otter (Lutra canadensis Schr.) and Cooper’s lemming mouse 
might be added as probable former residents (143, 21). 
Field stratum: This is confined to hummocks supporting herbaceous 
plants. Insects, spiders (159), etc., are common; some characteristic 
species occur. 
Tree stratum: The brindled grasshopper (Melanoplus punctulatus) 
(Fig. 146) has been found on the low branches of the tamarack and 
deposits its eggs on the bark of the trunk or on stumps. Several other 
insects have been recorded as common on the tamarack, among which 
are a sawfly, an earwig (Fig. 147), a lappet moth, and a woolly aphid, 
but we have not taken all of them. (See 137, II, 838, and I, Plate 18.) 
The tamarack is infested by bark beetles. In the swamp at Mineral 
Springs, Ind., we found one (Polygraphus rufipennis) (137), sometimes 
also Dendroctonus simplex Lec, common under the bark of partially dead 
trees (Fig. 149). The larvae of the clerid beetle (Thanasimus dubius) 
(Fig. 148) (137) occur with the bark beetles and feed upon them. 
The adult of the clerid (137) appears in spring, having wintered over 
as adult or in the late larval or pupal stage. It goes about on the 
bark of trees, seizing the bark beetles and later laying eggs at the 
openings of their galleries. The larvae invade the galleries and feed 
upon the eggs and larvae of the bark beetles. Felt states that two 
other bark beetles attack the tamarack (160). In this marsh the bark 
beetles have killed a number of trees. In summer the area of dead ones 
may be seen a mile away. 
