October, '23] 
cutright: micromus life history 
449 
nation of everything under the watch glass could then be made with little 
trouble and in this way the number of larval instars was established. 
Life History 
The eggs are found on the underside of the leaves of plants, usually 
those that are infested with aphids but not always. They are placed in 
irregular groups, containing one to thirteen eggs each, some may touch 
but others may be a centimeter or more apart. The long axes of the eggs 
frequently parallel each other but exceptions to this are almost the rule. 
They lie perfectly flat on the leaf surface to which they are rather inse¬ 
curely attached. There is no sign of the egg being stalked. Eggs were 
collected in the field from June to the first of October. Though never 
abundant a few hours search would usually bring several to view. 
Females that were confined in cages with aphid infested plants placed 
the eggs in the same relative position as those found in the field. When 
they were confined in vials or in petri dishes the eggs were deposited on 
the nearest convenient surface regardless of what it was or of its position 
relative to light. 
Several incubation records were taken in August and September. 
The average length of time required for hatching is four days with varia¬ 
tions of only a few hours, more or less, from this period. 
The larvae are easily the most conspicuous of the different stages. 
Their usual habitat is, as might be expected, plants that are infested with 
aphids, where they are found on the lower surfaces of the leaves or run¬ 
ning up and down the stems. I have collected them usually on herba¬ 
ceous plants. Banks states that they are common on aphid infested 
trees where they are found on the leaves. 
The larvae, in hunting for food, move about the leaf changing direction 
frequently. If the movement is slow the tip of the abdomen is usually 
attached to the leaf, the legs carry the body forward till it is stretched 
out as far as possible. The tail is then released, the abdomen is humped 
up and the tip re-attached. If the movement is rapid the abdomen is 
carried elevated, not touching the leaf, usually being humped about the 
fourth and fifth abdominal segments. All the time that movement is 
going on the head is continually being shifted jerkily from side to side. 
This is a very characteristic action on their part. 
The palps and jaws seem to be the structures used in locating food. 
The antennae touching the aphid bring very little response on the part 
of the larva. When a live aphid is located the head is drawn back and 
then thrust sharply forward, the mandibles piercing the body wall. I 
