1922] Uichanco — Notes on Parthenogenetic Macrosiphum 
71 
that they do not follow any regular schematic sequence. Further, 
it appears that no two legs move synchronously in the same 
direction, and that there is no definite rule as to the order in 
which the legs follow one another. The time intervals between 
successive steps, irrespective of the sequence of leg movements, 
appears to be maintained at a uniformly similar rate for a given 
speed. 
Summary of Section II. 1. The principal method of 
locomotion, even in alate individuals, is walking, the feeble 
wings being used rarely. 
2. The rate of diagonal swaying of the antennae and the 
rapidity of walking appear to be correlated, the movement of the 
former being in direct proportion to that of the latter. 
3. The movement of the legs do not follow any regular 
schematic sequence, although the time intervals between suc- 
cessive steps appear to be uniformly maintained in a given speed. 
No two legs move synchronously. 
III. Feeding Habits. Macrosiphum tanaceti has been 
known to occur only on Tanacetum vulgare Linnaeus. This 
species of aphid apparently has no secondary host plant. 
No attempt will be made in the present work to describe 
the mechanical and physiological relation of the mouth-parts to 
the plant tissue during the process of feeding. Considerable 
work has been done in connection with this problem in com- 
paratively recent years, notably by Biisgen (1891), and by 
Zweigelt; the latter author has been working on this and related 
subjects during the past decade. Zweigelt (1915) suggests the 
following three possible means by which suction of plant sap is 
accomplished in aphids. 
“1. Eine bestimmte Zelle wird angestochen und ohne 
Verletzung der ausseren Hautschicht des Protoplasten ausge- 
saugt; 2. die Aussaugung bestimmtcr Zellen erfolgt wahrend 
deren vollstandiger Durchbohrung; 3. die Aussaugung gcht 
zufolge einer dem Speichel innewohnenden starkcn osmotischen 
Saugkraft bei interzcllularem Stichverlauf ohne mechanische 
Verletzung der Zellen vor sich.” 
