22 ILLINOIS BIOLOGICAL MONOGRAPHS [416 



meet the distal pigmentation (Zeleny, 1907). The extent to which it 

 goes differs in different species and gives a faint pattern to the parts in 

 some species. The pigmentation which begins distally, usually pro- 

 ceeds only through the extent of the more distal segments (Fig. 

 109 a to e). By the end of 24 to 36 hours (Fig. 104) the pigmentation is 

 nearly complete by development over the general areas of both body 

 and appendages. Thus in the antenna at the end of 8 to 10 hours rings 

 appear toward the distal end of the three proximal segments, darken 

 and spread toward the proximal ends of the segments rapidly (compare 

 Figs. 109 c, d, and e). The pattern shown in the antennae, legs, 

 mandibles, palps, etc., persist in some species (see page 24). 



At 3 to 6 hours after emergence (Fig. 105a) the suture between the 

 clipeus and head becomes pigmented. By the end of 8 hours after 

 emergence there are two oblique color centers between the centers of 

 the eyes; these correspond in position to the oblique depressions 

 that occur in the genus Tetracha. Beside these there is a center close 

 to the posterior side of each eye, one just behind and inside of this, 

 and one in the middle of the frons (Fig. 106). Pigmentation then has 

 proceeded backward on the clipeus, and backward from the suture of 

 the clipeus on the head (Fig. 106). At the end of 12 to 15 hours, the 

 pigment of the clypeus and anterior part of the frons and centers just 

 described) has increased and extended backward, giving a pattern as 

 shown in figure 107. This process continues with general suffusion 

 over the head with the pattern still in evidence at the end of 24 to 36 

 hours (Fig. 108). 



After 8 to 10 hours after emergence (Fig. 106) the posterior border 

 of the thorax shows two centers in the depression at the posterior side. 

 Little change takes place on the under side from emergence. By the 

 end of 12 to 15 hours (Fig. 107) the thorax has presented some new 

 centers, a longitudinal stripe occurs near each margin, and there is a 

 narrower one between each of these and the center, and the anterior 

 depression is darker than usual. The end of 24 to 36 hours (Fig. 108) 

 shows the obliteration of the centers mentioned above by the pigmenta- 

 tion of the inter-spaces. 



On the ventral side of the abdomen and thorax pigment begins 

 on the outer side of the more posterior segments first and centers appear 

 from behind forward. During the first few hours the pigmentation 

 does not begin on the remainder of the abdomen. The next center to 

 appear is the one in the center of each segment near its anterior side, 

 which appears between the 6th and 10th hour. Just a little later a line 

 appears across the posterior side of the segment and there is an exten- 

 sion of the center one at each side and the coming in of the a loop-like 

 addition outside of the first center. This system of markings is best 



