IOWA ACADEMY OF SCIENCES. 227 



DIASPIN^ — THE ARMORED SCALES. 



In this group the adult females are permanently fixed and 

 covered by a scale separate from the body and formed by the 

 exuviae and waxy secretions from the dorsal surface. The 

 legs and antennas become useless and much aborted, while the 

 anal segment is specialized and furnishes the most important 

 structural characters, — visible only with the compound micro- 

 scope. 



Parlatoria ziziphe Lucas. 



I have on one occasion secured specimens of this species 

 from lemon bought in the market at Ames*. It occurs in enor- 

 mous abundance on the orange in the vicinity of Naples, Italy, 

 and the fruit, branches, and leaves exposed in the Naples mar- 

 kets are often loaded with the scales. Its black color and the 

 quadrangular form of the scale are striking characteristics 

 that enable one to recognize it at a glance. 



Mytilaspis pomorum Bouche. 



This, the "Oyster Shell Bark Louse, " which attracted much 

 attention some twenty to twenty-five years ago, and which for 

 many years caused great hav'oc in the orchards of the state, is 

 still to be met with in many orchards but in most cases in 

 rather limited numbers. At present it occurs in considerable 

 abundance on certain lilac bushes at Ames. 



Various agencies appear to hold it in check during most of 

 the time, and its recognition and subjection present no such 

 serious problem as confronts us in the case of perniciosus. 



Mytilaspis citricola Pack, 



This can scarcely be called a member of our fauna, as its 

 occurence in the state is dependent on its attachment to oranges 

 and lemons that come into our markets Its frequent appear- 

 ance in this manner is, however, sufficient reason for its men- 

 tion here, and it may easily occur on trees in greenhouses, as do 

 a number of tropical Coccids that have now a world wide dis- 

 tribution. 



Chionaspis salicis Linn. 



The white glistening scales of this species, often covering the 

 branches of willows, makes it a very conspicuous species. It is 



*This is possibly from imported fruit, as I Icnow of no records of the occurrence of 

 the species on trees in this country. 



