332 KANSAS UNIVERSITY SCIENCE BULLETIN. 



length of the pupal stage, as we observed it in September, 1911, 

 and eight days for the incubation of the eggs, we get the length 

 of the larval stage in the warmer months to be about two 

 months and three weeks. For the life cycle of the spring brood, 

 that leaves a period from the latter part of October to the first 

 part of April, or about five and one-half months. Since it is 

 in the larval stage that they winter over, it would indicate that 

 the winter temperature prolongs the length of the larval stage 

 for the spring brood. 



Newly hatched larvae are a pale creamy color, and about one 

 millimeter in length. They possess indications of the same 

 general characteristics of form and structure that the full- 

 grown larvse have. The color soon darkens to a slaty green. 



A full-grown S. vittatum larva measures from five-sixteenths 

 to three-eighths of an inch in length. The body is somewhat 

 attenuated in the second abdominal segment and gradually in- 

 creases in size in the third, fourth, fifth and sixth segments. 

 Beginning with the seventh segment there is a much increased 

 or abrupt expansion that gives the larva a widened and flat- 

 tened appearance. 



The metathoracic and mesothoracic segments and the first 

 six abdominal segments are cylindrical. The prothoracic is 

 thickened dorso-ventrally by the attachment of the single pro- 

 thoracic leg. (Plate XXXIX, fig. 11.) The head is semi-flat- 

 tened, with a slightly constricted neck, and is about the length 

 of the thorax. 



On the head are some very unusual prehensile organs, used 

 to collect food from the rippling water. They are fan-like in 

 shape, with forty filaments or rays in S. vittatum. (PI. XLT, 

 fig. 31.) \Vhen disturbed, or when the larva is taking food 

 from the rays with its mandibles and maxillae into the mouth, 

 the fan is closed so that the tips of the rays come just to the 

 oral opening. These rays are scythe-shaped, ciliate on the 

 inner side, with longer setse at regular intervals. (PI. XLI, 

 fig. 31.) The rest of the mouth parts, labrum, mandibles, 

 maxillpe, hypopharynx and labium, together with the antennae, 

 are shown individually and compositely arranged on plate 

 XLI, figures 32-35. Between the fans are the slender five- 

 jointed antenna; the fifth joint is a pointed process at the end 

 of the fourth. Back of the fans on each side of the head ar=; 

 two narrowly separated black spots. These may be eyes, or 

 light organs. Besides the leg or foot, on the sides of the 



