1314 Roger C. SmirH 
the floor of the pharynx. But the most striking musculature is about the 
pharynx. There is a series of muscles from the pharynx to the dorsum 
and the venter of the head, as well as to the arms of the tentorium. 
When these pharyngeal muscles are contracted, the lumen of the 
pharynx is increased and the juices are sucked up by a typical sucking 
action. But the muscles in the maxillae also contract and assist the 
pharyngeal muscles in their work. The opening at the tip of each jaw 
is single, and is formed by a curvature in both and not in the maxilla 
alone. The mandibles are sharp at their tips and constitute the piercing 
agency. 
The number of aphids that a larva may eat at one feeding depends, 
of course, on when it was last fed, on the size of the aphids, and on the 
size of the larva. A hungry third-instar larva will eat ten cabbage 
aphids in rapid succession. From ten to twenty larger aphids usually 
suffice for a day’s supply, though more were usually given. 
From hatching to pupation, a larva may devour from ninety to two 
hundred and fifty aphids, depending on their size. The following table 
is an accurate count of the number of aphids consumed by three larvae 
of C. oculata, by instars, from hatching to spinning: 
Date Date of Date of Date of Total number 
hatched|first molt] second molt | sninning of aphids eaten 
Larva No. 1 June 1 June 7 June 13 June 18 
Number of aphids 
eaten, by instars 38 48 68 154 
Larva No. 2 June 1 June 7 June 13 June 23 
Number of aphids 
eaten, by instars 35 68 99 202 
Larva No. 3 June 1 June 7 June 14 June 19 
Number of aphids 
eaten, by instars 46 60 50 156 
Average number of avhids eaten by each larva... 171 
Buckthorn and spiraea aphids were used in this test, and a special effort 
was made to get aphids of uniform size. At another time a more exten- 
sive count was made, using 22 larvae and rearing them through to spin- 
ning. In this case 3036 aphids were required, or an average of 138 to 
each larva. The rather large black aphids on lamb’s-quarters (Chenopo- 
dium album) were used for this test. 
Anal proleg of larva 
The anal proleg, or tail, is used to excellent advantage by the larva 
throughout its whole life. 
the larva is running very fast. 
It is always used in locomotion except when 
surface or extended horizontally. 
running. 
Then it is either merely lifted from the 
In the former case, the abdomen is 
curved and the end is held just above the surface on which the larva is 
This condition prevails when there is a possibility of the 
