APPENDIX 



319 



Fif^. (i — Thiril stage of the hir- 

 va; embryos becoming evi- 

 dent; enlarged. 



dew, of which they are very foad, and, in return, j^ather and care for the 

 eggs of the aphids during the winter, colonizing the young in the spring on 

 the proper plants. No such relations exist, however, in the present case. 



Unlike most other insects, plant lice absorb more food than they can 

 possibly a.ssimilate. They are constantly engaged in pumping out plant 

 juices, and what they cannot use is excreted, 

 either in little droplets through the honey tubes 

 or in minute jets through the anal opening. It 

 is in this way that they cause the glazed or var- 

 nished appearance upon the leaves below them, 

 and form the bed upon which the black soot 

 fungus already mentioned finds its favorable 

 opportunity to develop. 



To return to our plant louse which has just 

 inolted. It has yet the same number of joints 

 in the antennje, but these are now more slender, 

 and there is a distinct sensory j)it at the end of 

 the third joint, while the single pit on the fourth 

 joint has changed to a little group of three or 

 four. 



April 2(), some specimens h id molted a sec- 

 ond time, and were now in their third stage, almost double their original 

 size. The eyes, which in the earlier stages are composed of a few large, 

 round ocelli, placed closely together, are now larger and composed of 



a greater number of smaller lenses. At the end 

 of the body a little hairy process has become 

 evident, and the third antennal joint shows an 

 obvious tendency to. divide into two parts. In 

 the mounted sjiecimens the forming young or 

 embryos are now visible through the body wall. 

 April 28, the fourth stage was reached by the 

 more advanced examples. They are now more 

 oval and seem to be more fully distended, while 

 the eyes are yet larger and more obvious, tend- 

 ing, indeed, to become a little pigmented. The 

 antennae are now five-jointed, a sensory pit is at 

 the tip of the fourth, and a group of them is at 

 the enlargment of the fifth joint. Now, also, the 

 peculiar scaly surface of the aphid feeler be- 

 comes obvious, especially on the terminal two 

 joints. Seen under the microscope, it appears as if the joints were irregu- 

 larly shingled from tip to base, the shingles varying in length, breadth 

 and form of the corners. This feature is best marked in the most 

 fully-developed stages : but it is traceable even in the earliest, on the ter- 

 minal joint at least. 



Fig. 7— Fourth stage of larva; 

 the antenniP further en- 

 hirged. 



