2 CIRCULAR 3 3 4, U. S. DEPARTMENT OF AGRICULTURE 



or whitish color with darker (yellowish or brownish) heads and 

 slight vestiture. Three pairs of short legs are attached to the 

 anterior fourth of the larva on its ventral side. In its usual posi- 

 tion — when not crawling — the grub lies curled up in the form of a 

 horseshoe. The surface is more or less shining, but is deeply wrin- 

 kled transversely. There are short spines or setae dorsally, and on 

 the end and ventral surface of the terminal posterior segment is a 

 definite arrangement of spines and hairs. This group of spines and 

 setae, as seen from beneath, is called the raster, and offers the most 

 obvious characters for field determinations. At or near the center 

 of this group there are, in many species, a number of dark, stout 

 spines arranged variously as a transverse row, 2 longitudinal rows, 

 or 2 curved or diverging rows. These conspicuously modified 

 spines are, in some species, sufficient for immediate identification 

 without reference to other characters. 



The next most useful features are on the head of the grub — the 

 color and " surface finish " of the head capsule and the structures 

 of the epipharynx. 



In most species the characters of the head capsule, epipharynx, 

 and raster are sufficient for determination, but in a few the claws 

 may be examined to advantage. In any case, the length and general 

 proportions of a grub should be noted ; some species are more slender 

 than others. The normal habitat may be a decaying tree, soil about 

 shrub and tree roots, leaf humus in woodland, the turf of lawns, 

 fields, and pastures, high or low sandy soil, the moist humus of 

 open swamps, etc. Any such distinct condition of environment is 

 generally helpful in making determinations. 



The epipharynx is the inner (or under) surface of the labrum, 

 although some of its structures extend back on the inner wall of 

 the clypeus. In order most successfully to examine the epipharyn- 

 geal structures, an incision should be made with a very small knife 

 along the clypeal suture which extends transversely between the 

 bases of the mandibles. The entire mass comprising the labrum 

 and clypeus is then turned over and placed in a watch glass of 

 alcohol. If fine particles of foreign matter obscure the structures 

 when the whole is examined under a binocular microscope, they may 

 be removed by careful manipulation of a small pointed brush. For 

 comparison with the drawings, the specimen should be examined 

 with the apex of the labrum pointing away from the observer (the 

 base of the clypeus toward him). Looked at thus, it will be seen 

 that somewhat below the apex there is a raised area or eminence 

 terminating in a sclerotized point or several large fixed spines. This 

 small mound could be called the sensory eminence, for on it are 

 various arrangements of sensillae. These appear as small dark 

 circles, usually in two sizes. At the base of the labrum are two 

 blackish sclerotized plates called the tormae. These extend inward 

 from the sides and may end in acute points or more rarely may be 

 fused with each other, thus forming a narrow dark band across the 

 base of the labrum. The shape of each torma should be noted as a 

 good character in determination. Between the apices of the tormae 

 are several special structures more or less specific in character. At 



