Proceedings, 1924 57 



by fiicli steni-mdtlifr. I'lii' liri' (if tliis sccdiid L:riiiTatiim lit'cMnni' winuril 

 Hnd leave the elm early in -Imie. 



The life-history of lanigera, the wndlly apliis of apple, differs here 

 fi'oni this and other species of Eriosoma, since an apterous viviparous 

 fieneration is produced by tlie stem-mot her. this second generation pro- 

 ducins' the spring migrants, wliereas with ulmi, as stated above, the 

 spring migrants are the direct progeny of the stem-mothers without an 

 intei'vening generation. 



The spring migrants, upon leaving the gall, fly to black currant or 

 gooseberry, often at a considerable distance ; infections having been 

 located on currants two miles from any elms. 



I'pon arrival on the currant they alight on tlie leaves and travel 

 down the stem to the ground, penetrating to a depth of from 1-4 inches. 

 They here deposit from 12-15 young each, which become the first genera- 

 tion of apterous root lice which gradually colonize the entire root system, 

 penetrating to a depth of three feet and often occur five feet from the 

 stem. 



This root louse, originally described as fodiens, is ]:)ale yellow, he 

 coming orange after the third moult. Either .'] or 4 moults occur, and the 

 adult louse then measures 1.8 mm. long by .I't mm. wide; they secrete 

 copiously a silky wax from a series of pores. These pores occur longi- 

 tudinally in two rows of four on the head and in four rows of fourteen 

 each on the thoracic and abdominal segments, one row being on each 

 margin of the dorsum, the other two rows equidistant between them. 

 Lice of the apterous root generations mature in about fourteen days and 

 commence reproduction, depositing 25-30 young each at a rate of rather 

 more than one per day. No complete series was reared through, but, 

 from the data obtained by several batches reared on pieces of currant 

 root in petri dishes buried in the soil of the insectary, it would appear 

 that from 5 to 6 root generations occur during the summer in British 

 Columbia. 



The colonies are readily located on currant roots by the masses of 

 wliite w^axy secretion, which indicates one or more lice, and persist for 

 some time after they die. 



Early in September pupae may be found in the soil, and the result- 

 ant winged migrants are leaving in large numbers by the middle of Sep- 

 tember, stragglers often continuing to emerge from the ground as late 

 as the middle of October. Tlie autumn migrants fly liaek to English elm. 

 where, alighting on the trunk and main bi-anehes. they de|.iiisit the sexeil 

 forms. 



The migrants are found must aliuiidaiitly at a height of from five to 

 seven feet from the ground, just lu'low tin- main itraiiehes. 



