OAK SCALE-INSECTS. 101 



51. The obscure scale insect. 

 Aspidiotus ohscurus Comstock. 



This scale insect was found by Professor Comstock on the leaves of 

 the willow oak. The following account is copied from his report in the 

 U. S. Agricultural Report for 1880: 



Scale of female.— The scale of the female is very dark gray, agreeing in color with 

 the bark to which it ia attached ; and as it is only slightly convex, its presence is 

 difficult to detect. It is somewhat irregular in outline, but nearly circular. The 

 exuviae are between the center and one side ; their position is indicated by a nipple- 

 like prominence, which is marked, as in many other species, with a white dot and 

 concentric ring of the same color. The ventral scale consists of a delicate film of 

 white excretion, and the lower half of the exuviae attached to the bark. Diameter 

 of scale, 3™"= (.12 inch). 



Female. — The body of the full-grown female is reniform, being only four-fifths as 

 long as wide and having the lobes of the penultimate segment extending back 

 nearly as far as the end of the body. The segmentation of the body is very indistinct ; 

 the color is a yellowish brown. The last segment presents the following characters 

 (Plate XII, Fig. 4): 



There are five groups of spinnerets; the median consists of about six, the superior 

 lateral of about twelve, and the inferior lateral of about eight. The oval pores 

 opening on the dorsal side of the body are to be seen very distinctly from below. 



There are three pairs of well developed lobes. The first lobe of each side is conical, 

 tapering anteriorly, and with the distal margin rounded ; there is often a small 

 notch on the lateral side. The distal margins of the second and third lobes are ser- 

 rate. 



The thickened part of the lateral margin of the segment becomes narrower ante- 

 riorly until near the penultimate segment it is a mere line. It is irregularly notched 

 and is terminated posteriorly by a prominent lobe. 



There are seven short club-shaped thickenings of the body wall upon each side of 

 the meson. Each thickening is rounded anteriorly and tapers posteriorly. They are 

 situated as follows: one terminating near the lateral margin of the fii-st lobe, one at 

 each side of second lobe, one midway between second and third lobes, one at each 

 side of third lobe, and one near the posterior end of the thickened lateral margin. 

 This one is often obsolete. Those terminating at the median sides of the second and 

 third lobes are narrower and shorter, and have their anterior ends directed laterad 

 more than the others. The remaining thickenings are of about the same length as the 

 median lobes. 



The plates are inconspicuous, and in no case extend as far as the lobes. There is 

 one between the median lobes, one between the first and second lobe of each side, two 

 between the second and third lobes, and two between the third lobe and the poste- 

 rior end of the thickened lateral margin. The last two are unequally bifid, the other 

 four are simple and truncate. 



On the ventral side the first pair of spines is obsolete, the second and third pores 

 are situated at the base of the lateral margins of their respective lobes, the fourth pair 

 is just laterad of the lobe of the lateral margin, and a fifth pair is situated about one- 

 third the distance from this lobe to the penultimate segment. On the dorsal side the 

 first pair is also obsolete ; each member of the other four pairs is situated in little 

 mesad of the corresponding spine on the ventral surface. 



Egg. — The eggs have not been observed, and several specimens of females in the 

 collection indicate that the species is viviparous. 



Scale of male. — The scale of the male is oval in outline with the protuberance cov- 



