c( involuted sericteries, or spinning glands, which unite to form a duct, 

 opening on the tip of the labiuni. These organs are also present in lar- 

 va- that do not spin cocoons. The nervous system consists of a cerebral 

 ganglion, connected by a pair of commissures surrounding the cjesopha- 

 gus, with the most anterior of a series of twelve ganglia, which extend 

 through the body on the ventral side of the alimentary tract. The tir^t, 

 or suboesophageal ganglion, is a fusion of the ganglia of the mandibular. 

 maxillary and labial segments of the embryo. The tubular heart lies 

 just under the dorsal integument and terminates anteriorly beneath 

 the brain. The pericardial cells float out into the body like a velum on 

 each side of the heart. The feebly developed muscular system con- 

 sists of longitudinal fibres lying in two latero-dorsal and two latero- 



ventral zones in the various seg- 

 ments. Another set of muscles, 

 which are oblique antero-pos- 

 teriorly, have their dorsal inser- 

 tions at the intersegmental con- 

 strictions near the stigmata and 

 their ventral insertions at the an- 

 terior border of the preceding 

 segment. Segmental groups of 

 oenocytes are suspended near 

 these oblique muscles. The tra- 

 cheal system consists of a pair of 

 longitudinal trunks which send 

 off short branches to the adjacent 

 stigmata. The greater portion 

 of the spaces between the above-described organs is filled with lobes of 

 the voluminous fat-body which shows through the transparent integu- 

 ment and gives the larva its shining white, greenish or pinkish color. The 

 undeveloped reproductive organs are clearly discernible as small bodies 

 in the postero-dorsal region of the abdomen, and the histoblasts, or 

 imaginal discs, are present as small, paired clusters of formative 

 cells in the hypodermis of the integument. They represent the adult 

 antenna?, legs, wings, copulatory organs, parts of the sting, etc. Each 

 histoblast receives a slender nerve. 



When the larva approaches its full size important changes occur 

 in both its external and internal structure in preparation for meta- 

 morphosis, or pupation. For an account of the internal changes, which 

 are too numerous and intricate to be described here, the reader is 

 referred to the works of Karawaiew, Berlese and Perez. The external 

 changes may be briefly considered. When full-grown the larva passes 



FIG. 42. Larva? of Pogonomyrmex 

 molcfaciens. (Original.) a, Adult larva; 

 b, young larva ; c, hair of same enlarged. 



