IOWA ACADEMY 01 SCIENCES. 135 



and less numerous toward the joint. They are longest on the posterior part 

 of the abdomen, but do not form a fringe. The eighth segment is drawn out 

 into a horny anal process. The last three segments are usually provided 

 ■with a number of backwardly-directed teeth, which Dr. C V. Riley has 

 described as follows: 



"Sixth joint at middle of hind mai'gin with two or three very small teeth 

 placed transversely, and with no lateral teeth; seventh joint at middle of 

 hind margin with a tranverse row of four teeth, and on each side with two 

 or three (often obsolete) teeth or tubercles; anal joint with the horny process 

 about half as long as the joint and pointed at tip, while at the base of the 

 process, on each side, a lateral row of four small closely placed teeth extends 

 to the underside, and finally on the disk of the joint three teeth, triangularly 

 placed, the posterior being the largest; behind this group, and just above 

 the base of the process, is another tooth, nicked at the tip." 



In many specimens the teeth of the sixth segment were simply indicated 

 by a more chitinous texture than the surrounding tissue. In others these 

 teeth are represented by very slight tubercles, while in still others, they 

 were larger, but indistinctly sepai'ated. 



By examining a large number of specimens it was found that the teeth of 

 the seventh segment were subject to considei'able variation. Usually there 

 were three placed transversely. In some there appeared to be four teeth 

 represented, the central one being the largest and most posterior, having a 

 small tooth on one side of its base, and two small ones on the other. In 

 still others there seemed to be five teeth represented. The large one same 

 as before and then two small ones at the base on either side. In the latter 

 case the four basal spines were placed in a gentle curve around the larger 

 tooth. 



Is there any way of accounting for the variation in this group of teeth? 



In one specimen having four teeth, one of the two basal ones seemed to 

 be very deeply nicked, while the other was not. In the case where five 

 teeth were present we could consider that both of the small basal: teeth 

 were very deeply nicked, even to such an extent that the two parts became 

 separated, thus presenting the appearance of four distinct teeth. The first 

 lateral teeth occur on the seventh segment. From a dorsal view some speci- 

 mens present only one lateral tooth, but further examination reveals two 

 or three. In one case five latei-al teeth were found, the central ones being 

 the larger. No important variations were found^in the aual segments, 

 although one of the four small teeth on either side of the anal process was 

 difficult to find. 



One very attractive feature of the color of the larva is the blending of 

 the bluish-green parts and the rosaceous markings of the abdominal 

 segment. 



TRANSFORMATION OF PUPA TO ADULT. 



When exposed to the air for a short time the pupa changes to a slightly 

 paler'color. Soon the longitudinal muscles of the al)domen begin to con- 

 tract and draw it forward in the surrounding pupa skin, and thus allowing 

 it gradually to assume its natural position. In this process the displaced 

 portions of the abdomen catch in front of the depressed divisions of the 

 segments, and by tending to assume their former position uses them as 

 points of support from which to force the body forward. 



