POTATO PLANT LOUSE. 245 



From the last of July, 1907, to October 11 (possibly later) both winged 

 and wingless viviparous forms were present in the insectary. With the 

 Orono material of August 16, individuals attacked by a fungus were 

 inadvertably introduced, and the fungus spread among all the uncaged 

 material keeping it so reduced in numbers there seemed danger of the 

 insectary observations meeting the same fate as those of the field. How- 

 ever, every opportunity by way of freshly planted material was given 

 them and the insectary was kept as dry as possible and enough of the 

 plant lice escaped the fungus to keep the situation interesting. 



September 23. After finding the true sexes upon the caged material, 

 careful canvass was made of the uncaged plants in the insectary and 

 numerous oviparous females (mostly still young) were found both upon 

 the potato and shepherd's purse, although more numerously upon shep- 

 herd's purse. No males were found at this time and later but two were 

 seen in copulation on the uncaged material, — one pair being upon shep- 

 herd's purse and one upon potato. The prevalence of the fungus 

 undoubtedly prevented the development of a greater number of the true 

 sexes. 



October 11. Insectary search showed the Nectarophora eggs near 

 some of the oviparous forms both upon potato and' shepherd's purse. 

 Many of the eggs were the glistening brownish black of well hardened 

 eggs but some were pelucid green showing that they had very recently 

 been deposited. They were upon the plants indiscriminately on leaves 

 and stalks. 



The appearance of the oviparous females and the deposition 

 of eggs with the uncaged material at practically the same time 

 as that of the forms that had been prisoners for 2 months 

 would indicate that these dates are about normal. In the 

 insectary the migration -from overcrowded potato stalks to 

 fresh plants seemed to take place irregularly and not at any 

 stated times, the condition of the infested plant apparently 

 influencing these movements. The fact that they seemed to 

 seek the fresh potato plants almost as readily as the peas or 

 the shepherd's purse might seem to indicate that if a similar 

 succession of new potatoes were supplied them in the field they 

 might not seek another host even there. As it is a wholesale 

 migration has taken place each of the 3 seasons these plant lice 

 have been under observation. 



It seemed reasonable to expect that such an enormous num- 

 ber of healthy plant lice as had migrated from the Houlton 

 potato vines late in the summer of 1906 might with careful 

 search be located on the alternate host. After several long and 

 tedious attempts during September, 1906, the writer, somewhat 

 chagrined, postponed the search until the following spring in 



