140 



good ventilation, intense light, and changing and a relatively dry 

 medium. The problems involved in these conditions vary accordingly. 



The relative scarcity of mollusks and myriapods in trees is in 

 marked contrast with their abundance in habitats in proximity to 

 the soil. In the Bates woods the cherry-leaf gall-mite, Acarus, is 

 arboreal, but spiders are almost entirely absent. The walking-stick, 

 Diapheromera, is arboreal in part, but its eggs fall to the earth and 

 hatch there. The Severins ('lo) have shown that the emergence of 

 walking-sticks from the eggs is influenced to a very marked degree by 

 moisture, dryness being distinctly injurious and moisture favorable. 

 The molting of the young animals seems similarly dependent upon 

 moisture, and may be prevented by keeping them in a "well-aerated 

 breeding-cage" (Severins, 'iic). This is another clear case of a 

 forest animal sensitive to moisture. To the fact that there is greater 

 moisture near the soil are therefore related the egg-laying habits and 

 the development of the immature insect, a development in marked 

 contrast with that of the strictly arboreal katydids. Of the katy- 

 dids, Microcentrum and Cyrtophyllus are distinctly arboreal through- 

 out life, as the eggs are attached to the twigs, and they are relatively 

 independent of the ground. Curiously the Bates woods specimen of 

 Cyrtophyllus was taken among low sprouts. Amhlycorypha, how- 

 ever, lives near the ground. The cicadas are distinctly arboreal dur- 

 ing the imago stage. The larvse of PapiUo turnus and cresphontes, 

 Upargyreus tityrus, Cressonia juglandis (and parasite), Telea, ath- 

 eroma, Basilona, Halisidota, Datana, Nadata, Heterocampa, Bus- 

 troma, Ypsolophus, and the slug caterpillar are all arboreal. Many 

 of these pupate on the branches or among the leaves and do not de- 

 scend to the earth. The sphingid Cressonia, however, pupates in the 

 soil. There is a marked tendency for the Lepidoptera to be com- 

 pletely arboreal. Even noctuid caterpillars such as Peridroma saucia 

 and its allies, which live during the day on the ground, climb trees 

 at night (Packard, '90, p. 173; Slingerland, '95). Many of the 

 gall-flies are limited to certain kinds of trees and are arboreal, as, for 

 example, the several species of Cecidomyia found in the Bates woods. 

 The same is true of certain cynipid gall-makers, such as Holcaspis, 

 Amphibolips, and Andricus. It will be seen that the above-listed 

 kinds are largely defoliators and leaf-gall producers. Ammophila is 

 a predator. Trogus and the small hymenopters (cocoons) on Cres- 

 sonia are parasitic. 



Among the animals which live for a considerable part of their 

 lives in or on the soil and a part in the trees, are the two cicadas, 

 Calosoma, Cressonia, Ammophila, and certain ants, although no special 

 observations were made to learn to what degree the ants patrolled the 



