362 



PSYCHE. 



[March 1896. 



able that the ants first acquired the 

 habit in the case of the underground 

 species h'ke the corn root-aphis. The 

 oviparous females of this form wander 

 through the galleries of the formlcar)', 

 occasionally extruding an egg and 

 then die. Of course any suggestions 

 as to how the first eggs came to be 

 carried thiough the winter can only 

 be speculative. It apparently is not 

 impossible that the ants noticed some 

 quality about the eggs as they were 

 first extruded which led them to 

 recognize them as a part of their 

 food-giving pets; or possibly the first 

 eggs were overlooked and allowed 

 to pass the winter where the motlier 

 aphid deposited them, and been dis- 

 covered in spring at the time the 

 aphides were hatching ; or the eggs 

 may have been first stored up for 

 food, and the surplus left over in 

 spring have hatched. However the 

 habit may have originated it evidently 

 is so useful to all it would be fostered. 

 Having once become an established 

 routine of the ants' yearly cycle, it is 

 not difKcult to imagine that thej' 

 would recognize the eggs of aphides 



living above ground, especially those 

 living in covered outside tunnels of 

 the ants, and thus gradually develop 

 the habit of carrying the eggs in and 

 the resulting young out. 



Passing now for a moment to the 

 group of aphides whose hibernating 

 condition is exemplified by the Woolly 

 Aphis of the alder (p. 359) it is easv to 

 see how natural elimination may have 

 brouglit about the existing conditions. 

 This species appears never to develop 

 any eggs : consequently it must pass the 

 winter in some living stage. The col- 

 onies of viviparous forms are constantly 

 bringing forth multitudes of livingyoung 

 which of course are more abundant in 

 autumn than at any other season. The 

 crowding produced by numbers would 

 often compel them to wander over all 

 parts of the shrub. Those reaching 

 late in autumn the bases of the main 

 stems would stand a much better chance 

 of surviving the effects of wind, snow, 

 rain and ice than those on other parts 

 of the tree. This constant elimination 

 of the unfit and the ' inherited memory ' 

 of the fit would lead to present condi- 

 tions. 



OVIPOSITfON AND HATCHING 

 THANAOS JUVENALIS. 



OF 



May 16, 1894, I followed a specimen of 

 T. jiivcnalis which was apparently search- 

 ing for a food plant among the scrub oaks of 

 Middlesex Fells at Maiden, Mass. The in- 

 sect flew down to tlie base of a small, six- 

 inch seedling of ^iierciis alba and laid a 

 single egg upon the stem of the plant, an inch 

 from the ground, among the tender, reddish. 



scale-like leaves. The act of oviposition 

 lasted about ten seconds, during which the 

 insect's wings were folded back to back, her 

 fore-feet grasping the stem, while the mid- 

 and hind-feet were rubbed quickly together 

 and along the sides of the abdomen, appear- 

 ing to assist the process of egg-laying. This 

 occurred on a warm, sunny day, an hour 

 before noon. The egg, delicately greenish 

 when laid, soon became white and within 

 twenty hours was orange in color. Seen 



