201 



(No. i). Milkweed flowers play a double role as food and enemy. 

 Robertson (Trans. St. Louis Acad. Sci., Vol. 5, p. 573) states that 

 honey-bees are frequently found hanging dead from the flowers of 

 the common milkweed, A. syriaca, and Gibson (Harper's Mag., Vol. 

 95, pp. 519-520. 1897) has found many of them entrapped by this 

 milkweed. Bees are not the only insects captured by this insect trap, 

 for Gibson found gnats, crane-flies, bugs, wasps, beetles, and small 

 butterflies hanging from the flowers. He also found that the dogbane 

 Apocynum thus captures moths. 



n. Forest Invertebrates 

 MOLLUSCA 



Polygyra albolabris Say. (PI. LI, figs. 2 and 3.) 



A single adult dead shell (No. 91) of this woodland species was 

 found in the upland forest (Sta. IV, a). It is our largest species of 

 snail. 



The natural history of our land-snails has received little attention, 

 but is worthy of careful study. The best account of the life history 

 and habits of this species is by Simpson ('01). 



Polygyra clausa Say. 



A single dead immature shell was taken under a small decayed limb 

 on the ravine slope (Sta. IV, b) Aug. 26 (No. 164), associated with 

 many individuals of Pyramidula perspectiva, and one individual each 

 of Vitrea indentata and V. rhoadsi. 



Shimek ('01, p. 200) groups this species with those which frequent 

 "higher, more deeply shaded (often mossy and rocky) banks and 

 slopes, sometimes in deep woods." 



ClBCINARnD^ 



Circinaria concava Say. Predaceous Snail. 



A large dead shell (No. 71) and several living specimens were 

 found in a decayed stump in the upland forest (Sta. IV, a). A young 

 individual (No. 113), diameter 6 mm., was taken Aug. 20 among the 

 vegetable debris washed from a ravine and deposited as a low fan in 

 the lowland forest (Sta. IV, c). With it were associated Vitrea in- 

 dentata, and some kind of large snail eggs (No. 114). This is a car- 

 nivorous species. 



