224 
IOWA ACADEMY OF SCIENCE 
the side of the head fold and in front of the mandibular segment, becoming 
somewhat thicker at the same time (PL III, a). The segments do not appear 
in the antennse until near the close of embryonic life. They then appear as 
constrictions of the already formed antennse, not by the addition of segments 
from behind. At the close of embryonic life the antennse are composed of three 
segments (PI. Ill, figs. 10 and 12-a). 
(b) The mandibles . 
The mandibles appear as appendages of the second segment. This segment 
is divided laterally into two parts, by the appearance of the gastrula invagina- 
tion and the stomodoeum, almost as soon as it appears (PI. II, fig. 8). Almost 
immediately the tw'o lobes move forward to the sides of the antennal segment 
(PL II, fig. 10-m). As the embryo develops these rudimentary mandibles be- 
come narrower and longer (PL III, figs. 5 and 7-md.) About six or eight hours 
before the time of hatching they have grown downward and are visible in a ven- 
tral view of the embryo (PL III, figs. 5 and 7 md.) A short time before hatch- 
ing they becom^e divided into two segm.ents by a very slight constriction, and 
the distal segment develops into a sharp pointed organ. This is the larval 
mandible. 
(c) The maxillae. 
The first maxillge develop as appendages of the third segment. This segment, 
like the mandibular segment, becomes divided by a dorso-ventral constriction 
almost as soon as it is formed, and begins to move forward as two lobes, which 
constitute the rudimentary appendages and their attachment. The anterior 
edge of this segment moves forward until it is slightly in front of and outside 
the posterior edge of the procephalic lobes. (PL III, figs. 2, 3 and 6, 1st mx.) 
The maxillse grow downward a.nd inwa,rd (PL III, fig. 11, 1st mx.), and just 
before the close of embryonic life a small segment is formed at the end. In 
the newly hatched larva there is visible a third, very srnall segment at the 
extremity of the maxilla. 
The second maxillas are very little developed. They appear as slight pro- 
truberances of the fourth segment. They are noticeable just before hatching 
(PL II, fig. 11-m). " 
id) The thoracic appendages. 
No appendages are visible upon the thoracic segments until near the close 
of embryonic life. About eight to ten hours before hatching there appear upon 
the first thoracic segment a pair of appendages. These are not as yet seg- 
mented and lie close together on the ventral surface of the embryo (PL III, figs. 
8, 10, 11 f.) These develop into blunt rounded appendages, upon the surface of 
which there appear, -just before hatching, a number of setae. These are notice- 
able in figures 8, 10, 11 and 12, Plate III. They serve as legs during the larval 
life of the insect. 
(e) Abdominal appendages. 
No abdominal legs were observed at any time. On the ventral surface of the 
last segment, however, appear a pair of large tubular appendages, fringed with 
