920 FIFTH REPORT OF THE ENTOMOLOGICAL COxMMISSION. 



Larva.— Boi\y swollen on the thoracic segments, and also a little humped on the 

 eighth abdominal segment. Head held down in a sphinx-like attitude, smooth and 



green. Body pale green, like a cedar leaf 

 in hue, and so mottled and marked with 

 yellowish green as to resemble the leaves 

 of the cedar with their yellow-lined scales. 

 A broken dorsal yellowish line, and a 

 latero-dorsal line of larger yellowish spots. 

 On each side of each segment are two longi- 

 tudinal yellow spots with a lateral one 

 between them, A lateral row of faint 

 yellowish patches. Length, S'"^. 



8. Phytoptua thujce Garman. 



According to Mr. H. Garman (in 

 Forbes's first report on the injurious 

 insects of Illinois) this mite occurs 

 on the leaves of the American arbor 

 vitae, Thnja occidentalis Linn., in 

 summer, and in the buds and under 

 the leaves in winter. 



" In the latter part of the summer 

 of 1880 my attention was called by 

 Prof. S. A. Forbes to the diseased 

 condition of arbor vitae hedges in 

 and about Normal, 111., and upon 

 searching the trees this Phytoptus 

 was found creeping about the leaves. 

 I was inclined at the time to refer 

 the condition of the hedges to in- 

 juries inflicted by the mites earlier 

 in the season, for they were not suf- 

 ficiently abundant at the time the 

 examination was made to cause 

 serious inconvenience to the plants. 

 Since then the trees have regained 

 their usual thrifty ap])earance, and 

 the mites, although still present on 

 them at all times of the year, have 

 not been more abundant at any time 

 than they were when first discovered. 

 The Phytoptus of the arbor vitoe 

 spends the winter in the buds and 

 under the margins of the leaves. It 

 can be secured in midwinter by bring- 

 ing infested twigs into a warm room." 



Adults of this mite measure from .005 to .0065 inch in length, with the greatest 

 transverse diameter about .002 inch. They are whitish and semi-transparent. Of 



Fig. 306. — Phytoptus thujce (ventral view) ; a, 

 lostruni ; 6, liibiuiu ; c, chelicer.T ; d, appear- 

 ance of ioints seen on the rostrum ; e, tarsal 

 claw ; /, feather-like tarsal appendage ; g, 

 one of the first pair of hairs on under side 

 of cephalothorax ; h, one of the second pair 

 of hairs on the under side of cephalothorax ; 

 i, genital plate ; j, abdominal sucker. — After 

 Garman. 



