ECOLOGY OF ISLE ROYALE. 77 



the fresli mould is turned over a few of the moisture-lovino; flies, 

 Hijdrophorus philomhrius ^A'heeler, appear and rest on the moist ex- 

 posed surface. 



The trees' themselves shelter a more varied population. Most of the 

 Buprestids and Cerambycids caught in the tent probably came from 

 the forest. The dead trees of balsam or spruce are attacked by wood- 

 boring larvae, which construct a network of chambers just between 

 the wood and bark. Some of these turn into the wood and extend 

 to the center, following a longitudinal or tangential path for most of 

 the way. These holes may be filled with dust part of the way, but 

 the greatest portion is em,pty. They are about 3 by 5 cm. in diameter, 

 of an elliptical shape, but at the ends sometimes widen out into cham- 

 bers a couple" of centimeters broad. Two species of larvae occupy these 

 burrows (No. 205), and in one was found a small s])ider, Amatirohhis 

 hennetti P>lk. (No. 205). 



Under the loose bark of trees which have decayed further spiders, 

 Aiiianrohutfi hennetti Blk. (No. 205), frequently build their webs. A 

 beetle, Caltithun adveiiu Le C. (No. 142), forages here for food, and 

 in one case a sliell (142) was taken. A nest of Formica sangidiieu 

 Latr. (No. 78) was found in the rotten wood of a fallen tree, but the 

 ants probably foraged over a rock clearing near by rather than in the 

 forest. In prostrate decaying logs the fauna is not. different from 

 that of the leaf mold, and the same species were collected. 



A number of the mushrooms of the genus PJeurotus were collected 

 on dead trees and they were inhabited by large numbers of beetles 

 (229) Tn'toiiKi thovucicu Say, T. nuicra Lee, Boletohiiis einrticollis Say, 

 and Grophacna S]). 



/J. Artificiul Clearings. 



The clearing about the camps both at Eock Harbor and at Siskowit 

 Bay attracted many species of insects, p.articularly strong fliers, such 

 as Hymemoptera, Lepidoptera and Diptera. At Rock Harbor Cow- 

 parsnip, Heracleimi lanatum,, introduced in the island some way, was 

 in bloom and it attracted a number of species of bees and flies. 



In a similar clearing on the north side of Eock Harbor a number of 

 shells were collected from the under side of dead logs (150). Some 

 of these were observed at no other place. They included Polygyra 

 albolahHs (Say), Acantltintila harpa (Say), Bifidaria tappaniana (C. 

 B. Adams), Zonitoides arljorea (Sa>), Pyranddula cronkheiti anthmuji 

 Pils., Coehlieopu luhrica (Miill), and TaUonia eostata (Miiller). A 

 plant of Opulaster blooming in the same clearing attracted a multitude 

 of insects (148), including the flies Platycliirus pcltatiis ileigen, 

 l^i/rpltus zenitulis Williston, Hphaerophoria eijlindricu Say, Eristalis 

 diinidiatus Weed and Temnostomu acqitalig Loew; the bees Halictns 

 rersans Lowell, Xanthosanis latiinaniis Say, and Bomhus tenicola Kby; 

 the beetle Lcptiira ehrysocoiaa Kby. and the lepidopteron Cnpido scpio- 

 lus Bd. 



X. Suiiimary. 



From the lake, i*epresenting the most primitive habitat, there are 

 three lines of development culminaKng in the climax association; first, 



