346 NEW YORK STATE MUSEUM 



prominent, in others not nearly so much so. They are perhaps openings 

 of glands which assist in the formation of the scale. Among these are 

 seen curious organs which may seem to be on the surface of the body 

 but are proved by focusing to occur within it in connection with external 

 openings. These have been denominated by Prof. Comstock the wax 

 ducts. In the explanatory figure a few are represented at m^ m, but not 

 in later figures, as they have not been shown to have definiteness ot 

 arrangement or classificatory value. 



The large circular opening on the dorsal side is the anus (pi. ii, fig. 

 m). Like the other dorsal organs it is visible from the ventral side also, 

 appearing as a clear area. 



I think no other organs of importance are present in the four species 

 here mentioned. There are sometimes visible a few minute round pores 

 and some small superficial spines, or hairs, but they may be disregarded. 



Distinguishing species. It is of course a commonplace in many 

 divisions of science, but perhaps in none more than in the study of the 

 Coccidae, that familiarity with forms is necessary for any great degree 

 of certainty in determining species. Descriptions of two or three different 

 species read marvelously alike, and even figures are not absolutely dis- 

 tinctive, because of the great variabiHty in species. Moreover, the 

 untrained eye does not quickly recognize differences, specially where dis- 

 tinctions must be largely comparative. Hence any key to species must 

 in the nature of things be unsatisfactory, for it must be relative in its 

 terms and so can not be used with large degree of certainty in each step 

 till familiarity with the species renders it unnecessary. However, it is 

 sometimes an aid in earlier studies through its emphasis of the more dis- 

 tinctive features, and the following is submitted with that end in view. 

 It applies only to the four species here farther characterized, and per- 

 haps may not exclude other species, which have not fallen under my 

 ken, so that it will be useful only when the student finds it probable that 

 he has one of these four, but is not sure which one. They are the four 

 species of Aspidiotus most frequently brought to the attention of 

 horticulturists in this state, a fact which may justify this limitation of 

 my study. 



This key will apply, I think, to the second stages as well as to the 

 mature females, though with hardly as much positiveness. I have been 

 unable to detect constant specific differences in forms before the first 

 molt. Sometimes the question may arise as to whether the form pre- 

 sented is adult or not. This occurs when neither ventral glands nor 

 eggs nor young are present. In this case if the ventral thickenings are 



