104 CAROLINE BURLING THOMPSON 



specimens were next transferred from cedar oil to xylol and 

 embedded in paraffin of 54° melting point for one hour or longer, 

 according to the size. The previous staining was found indis- 

 spensable for orienting the insect in paraffin. Most sections 

 were cut in the horizontal, frontal, plane, 5 micra thick, and were 

 stained on the slide with iron haematoxylin and orange G. The 

 chitin is so thin in the youngest nymphs that complete series of 

 sections can be obtained. 



C. SCOPE OF THE WORK 



My work deals chiefly with the development of the nymphs of 

 L. flavipes, from the time of hatching, when they are about one 

 millimeter long, up to the first molt, when they have attained a 

 length of 2.25 mm. The newly hatched nymphs and a few of the 

 older phases of the southern species, L. virginicus, have been 

 studied, but not with the sequence and detail given to L. flavipes; 

 enough has been done, however, to state that the development 

 of the two species is very similar and probably identical. To 

 determine the origin of the soldier caste of L. flavipes, older 

 nymphs, from 2 to 4 mm. long have been studied. 



D. THE DEVELOPMENT OF L. FLA\IPES, FROM THE TIME OF 

 HATCHING (1.1 MM.) TO THE FIRST MOLT (2.25 MM.) 



The period between hatching and the first molt was called 

 stage I by Grassi, who described it for Leucotermes lucifugus 

 as follows : 



'T. Very young larvae, the head of which is alike in those 

 of equal length." 



These Grassi divides into: Forms scarcely 1 mm. long, anten- 

 nae of eleven segments, the third bare; Forms 1 to 2 mm. long, 

 antennae with eleven hairy segments, or twelve, the third and 

 fourth bare; Forms 2 mm. long, antennae with twelve segments, 

 the third bare. 



Stage II of Grassi consists of forms from 2.25 mm. to 3.75 mm. 

 long, with twelve or thirteen antennary segments, and contains: 

 'Larvae' with large heads, and 'Larvae' with small heads. 



