132 BOTANY OF MICHIGAN 



It gradually worked its way westward and arrived in Michigan soni3 

 ten years ago or thereabout. The naked larva which feeds on the leaves 

 in June and July, when full grown, goes to the ground and pupates just 

 under the surface. The creature being from Europe has no natural 

 enemies or very few of them to control it here, and therefore the death 

 rate of tamaracks has been very high. It usually is followed by a bark 

 beetle which works between the bark and the wood and which is itself 

 capable of killing trees. The name of this saw fly is Lygaeonemalus 

 erichsoni, and the name of the beetle that works under the bark is 

 Denbroctonus similis. We have been spending some effort for a number 

 of years trying to introduce the European parasites which control this 

 pest in its native home and while we have not succeeded in establishing 

 the European species we have some little hopes from an unknown species 

 which we have succeeded in getting several times. There is nothing 

 that can be done particularly. " — B. H. Pettit, Professor of Entomology, 

 Michigan Agricultural College, February 18, 1915. 



Picea canadensis (Mill.) BSP. White spruce. Scattering throughout 

 along Lake Superior shore and on sand ridges. Often affected with a 

 pest known as dwarf mistletoe. 



Picea, mariana (Mill.) BSP. Black spruce. Large areas of this mixed 

 with tamarack growing in wet swampy ground throughout the county. 

 Trees mostly small. Often growing on higher ground, where it is larger and 

 cut for pulpwood. A form of it common on dry sandy land everywhere, 

 and on sand ridges, which some botanists would name P. brevifolia Peck, 

 swamp spruce. Twigs of this and Abies balsamea near Lake Superior 

 shore above Shelldrake, are covered with a bearded lichen, Usnea barbata 

 plicata Ehrh., giving the trees a shaggy and moss-like appearance similar 

 to more northern forests. Often afflicted with the dwarf mistletoe. 



Abies balsamea (L.) Mill. Balsam fir. Common throughout the 

 county and abundant in spots. Frequent with beech, maple and birch, 

 and occasional in swamps with tamarack and black spruce. A very 

 beautiful forest tree. 



Tsuga canadensis (L.) Carr. Hemlock. Common throughout but 

 seldom abundant except in streaks or small spots. Frequent with hard 

 maple, yellow birch, and beech. Trees often very large, one recently 

 cut indicating an age of over 300 years. Large trees called "yellow hem- 

 lock" by land cruisers; second growth, "white hemlock". 



Thuja occidentalis L. Arbor vitae, white cedar. Formerly very abun- 

 dant throughout the county in cedar swamps which have been lumbered 

 over for many years and mostly destroyed by fire. Small trees and seed- 

 lings yet abundant. Often growing on sandy ground especially near 

 the Lake Superior shore, but it is usually small in such situations. 

 Shrubs and seedlings abundant. As understood by land cruisers, sec- 

 ond growth trees and trees covered with limbs to or nearly to the ground 



