610 CAROLINE B. THOMPSON AND THOMAS E. SNYDER 
The worker of R. flavipes 
The worker is found only in the nymphal and adult phases, 
since no postadult growth takes place as in the reproductive 
forms. 
The development of the worker is a simpler process than that 
of the fertile castes and requires a shorter period of time—one 
year or less, instead of two. The newly hatched nymphs with 
the small brain and small sex organs, the ‘worker-soldier’ nymphs, 
give rise to both workers and soldiers, and in the early phases 
of development there are no external features to distinguish 
these two castes. With a body length of 3.75 mm. the two may 
be distinguished by internal features—size of the frontal gland 
(Thompson, ’17)—but after a length of 4 to 4.5 mm. is attained, 
the worker and soldier are externally different. 
The worker nymph differs from the adult worker only in size 
and a lighter body color. 
The adult worker is 5.5 mm. long (fig. 7), the head is very 
similar in size to that of the third-form adult, but is yellowish, 
on account of the thick chitin (fig. 31). The compound eyes 
are small and practically invisible except with magnification. 
The thorax is wingless. The abdomen is rather blunt in outline, 
as compared with the reproductive forms, the skin appears thin 
and transparent, on account of the very few masses of fat cells 
in the body cavity and the many empty spaces, filled only by 
body fluids. The woody contents of the large intestinal sac, 
or caecum, show clearly through the skin, giving a grayish color 
to the abdomen, a good field mark for this worker. Genital 
appendices are present on the ninth abdominal segment of both 
Sexes. 
The internal structure. The brain (fig. 10), especially the optic 
lobes, and the compound eyes are greatly reduced in size; the 
frontal gland is a mere vestige, not glandular; the lateral ocelli 
are lacking. The reproductive organs are non-functional, having 
remained in an early embryonic stage of development. In the 
female, the three fundaments of this system have not undergone 
fusion, and the ovaries and ova are very minute (fig. 27). In 
