THE BIOLOGY OF THE CHRYSOPIDAE 1315 
larva’s falling, as in climbing up on the side of a jar or a plant. It is 
the safety agency in the larva’s descent along the stalk after hatching, 
and it is the larva’s main dependence for surety in climbing up and 
down plants, twigs, glass, and the like. It is used also to brace the body 
when the larva is handling a struggling aphid. 
Reference has been made to a disklike ending of the abdomen. This 
disk is appled to the supporting surface, and a sticky or gelatinous sub- 
stance is exuded which enables it to hold fast. At first observation it 
may appear that the larva holds fast by suction, as stated by Fitch 
(1855). If a larva be allowed to walk over a fresh, green, smooth leaf, 
and the highest-power binocular objective be directed upon the tail and 
the spots covered by it, the little disks of viscous fiuid, more or less com- 
plete, can be seen on the leaf. It can also be readily seen that the end of 
the abdomen is immersed in a drop of this clear liquid. 
Larval excrement 
There is no voidance of larval excrement. It has been known for a 
long time that the mid-intestine is closed behind (Lurie, 1898, and Me- 
Dunnough, 1909), and the excrement is stored up in a bean-shaped mass 
throughout the life of the larva. The darkened appearance of the 
anterior part of the abdomen is generally due to this black mass within. 
It is rather surprising that the mass from the entire larval life is so 
small, but the explanation les in the fact that the food is hquid and the 
amount of residue is small. 
Classification of larvae 
The first basis for classification of the larvae is the marks on the 
head. These serve to class .the larvae into groups which for the most 
part appear to be most closely related as adults. After the head marks, 
the general coloration of the body is used. The color of the metathorax 
varies in the different species. The color of the margins of the thorax 
and the abdomen are often specific. The first abdominal tubercles differ 
shghtly as to their degree of development. The following key is for 
third-instar larvae: 
A. Two prominent, black, elongate spots on dorsum of head. 
B. Spots extending longitudinally, converging posteriorly. 
C. Jaws amber-colored; legs with smoky or darker patches on femora, 
but not predominantly dark. 
D. Body of larva brick red or darker above; without a wide gray 
border on each side of dorsal vessel; yellowish border each 
side of abdomen; thorax with a prominent yellowish spot 
around base of each lateral tubercle... C. rufilabris Burm. 
