Nov., 1911.] 
Life-Histories of Syrphidae II. 
399 
The anus is ventral on the last segment. 
These larvae were first taken at Columbus, Ohio, on May 31, 
1911, when a dozen or more of various sizes were collected on 
Curled Dock (. Rumex crispus L.) very badly infested with an 
aphid ( Myzus sp.). 
On June 4, eggs and larvae were taken from the same host, 
the eggs hatching the following day. The young thus made their 
first appearance at this station the latter half of May and the 
first of June. At Lakeville, Ohio, seventy miles north-east, 
larvae of differing sizes were collected from both Curled Dock and 
Broad Leaf Dock ( Rumex obtusijolius L.) June 15-18. At San- 
dusky, on Lake Eric, larvae of this species nearly full grown were 
collected from Curled Dock on June 21 and July 1. At Castalia, 
June 29, larvae were abundant on Common Burdock ( Arctium 
minus Schk.) On July 8 both pupae and larvae were taken in 
considerable numbers from Burdock at Kelley’s Island. Again on 
August 27th larvae were found on thistle ( Carduus sp.) at 
Lakeville, Ohio, among aphids ( Aphis sp.). 
From all the observations made on this species two distinct 
generations seem evident : one appearing in spring at dates varying 
from the middle of May to the middle of June or a little later in 
different parts of the State, a second appearing in August and 
perhaps later. 
On Rumex these larvae are to be found among the aphids 
U/\ >z us sp.) which cluster especially on the heads or flower 
spikes and the smaller leaves; on thistle on the upper tender parts 
of stems; on Arctium they are more especially on the under side 
of the large lower spreading leaves. They are parasitic on the 
aphid colonies catching the individuals with their mouth-parts 
and killing them by slowly picking out and sucking out all the 
soft body-contents within the chitinous wall. During this 
process the mouth parts are manipulated by strong muscles 
which also move the large chitinous plates about the oesophagus 
out and in like a battering ram. The anterior two or three seg- 
ments are pushed inside the sac-like body- wall, and the contents 
very carefully and completely picked out all around and into the 
bases of the appendages. Empty skins are dropped and may 
sometimes be noted. 
The larvae arc sluggish when plenty of food is at hand, usually 
nicely protected by position among the aphids and somewhat by 
colors similar to those of the host plant. They can, however, 
move actively by looping movements with the assistance of the 
pro-legs. When in search of food the larva advances a short 
distance, raises the anterior half of the body and lashes it rapidly 
from side to side, then advances again and repeats the side lashing 
until it touches the desired food. 
