June 5, 1916 



Woolly Pear Aphis 



357 



hyalin antennae and legs and black eyes of three facets. The insect 

 becomes darker with age and the mature individual is dark olive-green, 

 sometimes tinted with lilac or purple, the central part of the abdomen 

 being darkest. The male is always narrow in shape. The female varies 

 in color from a light orange to a dark red. The eyes and appendages 

 are as in the male. The majority are orange or a light crimson-lake. 

 They are mxuch stouter than the males and are longer and stand much 

 higher. A mature female measured alive was 0.67 mm. long by 0.33 

 mm. in maximum width. A mature male was 0.43 mm. long by 0.21 

 mm. in maximum width. 



Copulation occurs as soon as the sexes are mature. It appears that 

 unless the female is fertilized directly after she has cast her last skin she 

 will fail to deposit the winter egg. The male may live at least a week 

 after he is mature, but apparently he can exercise the sexual function 

 only immediately after he has cast the last skin. The females deposit 

 the impregnated egg imm^ediately after copulation, and after its deposi- 

 tion they may live for a day or two at the most. The winter or impreg- 

 nated egg is laid normally in crevices or scars of the bark of the elm. In 

 the dishes it was laid sometimes on the outside of the bark, and both 

 elm and pear bark were used. It was never laid elsewhere than in the 

 bark. The egg measures about 0.444 ™ni. by 0.225 mm., is short oval, 

 reddish yellow, and shining. The end first extruded is reddish and bare, 

 while the other extremity is yellowish and usually covered with short 

 white wool provided by the female. Winter eggs were deposited in 

 dishes between October 15 and November 12. Undoubtedly they occur 

 in nature as early as September 5, and may be laid as late as the middle 

 of November. Toward the end of October some were collected under the 

 bark of elms under observation. Table I is a comparison of the biology 

 of Eriosoma pyricola with that of E. lanigerum. 



Table I. — Comparison of biology of Eriosoma pyricola ziiih that of Eriosoma lanigerum 



in California ' 



Eriosoma lanigerum on apple and varieties of pear. 



Eriosoma pyricola on pear. 



Aerial and radical. 

 Attacks trunks, branches, and 

 causes knotty swellings on roots. 



twigs; 



Fall migrants rarely abundant; apparently 

 not influenced by conditions. 



Radical only. 



Attacks chiefly fibrous rootlets; rarely 

 causes lesions; occasionally settles on 

 larger roots. 



Fall migrants very abundant under fav- 

 orable conditions. 



• The full cycle of these species has not been 'worked out in California, but there appear to be no records 

 of spring generations of E. lanigerum observed on elm. 



The fall migrants of E. pyricola may be distinguished from those 

 of E. lanigerum and E. americanum as shown in Table II. 



