1917] Studies on Hydromyza Confluens Loew 39 



THE LARVA 



Process of Hatching. — The place of emergence of the larva 

 from the egg is a constant feature. The larva makes an exit hole 

 through the egg capsule near the blunt, concave end, on the side 

 next to the petiole. The position of the exit hole is determined 

 by the position of the larva and is directly in front of the 

 chitinous mouth armature, which, no doubt, is the instrument 

 by means of which the opening through the shell is made. The 

 exit hole is usually more or less circular in outline and somewhat 

 larger than is necessary for the passage of the body of the larva. 

 Occasionally, hatched eggs show a more extensive breaking 

 down of the chorion next to the petiole. The larva bores 

 directly into the petiole and there passes its entire existence. 

 No evidence whatsoever was observed of any preliminary 

 wandering of the larva after emergence from the egg. The 

 latter always marks the position of the future abode of the 

 resulting larva and pupa. 



Recently Hatched Larva.— On emergence from the egg, the 

 larva is milk-white in color, with the exception of the black 

 mouth armature and the blackish caudal projections. The body 

 (Fig. 6) is cylindrical, elongate, slender, and smooth. Measure- 

 ments, made on living, recently hatched specimens, show a 

 rather constant length of from 2.33 to 2.5 mm. The maximum 

 diameter, in the region of the future thoracic segments, is 

 approximately 0.29 mm. Intersegmental grooves are distinct 

 but shallow. The anterior end of the body is rather bluntly 

 rounded and shows no special structures, except the emergent 

 teeth of the mouth armature. Posteriorly, the body is distinctly 

 tapering and terminates in a pair of acute chitinous projections 

 which bear the terminal spiracles. The integument is covered 

 with very fine, pointed, conical projections. They are uniform 

 in size and shape over the body except on the anterior margin 

 of the first thoracic segment where they are a little more dis- 

 tinct. In most specimens, the translucency'of the body allows 

 the principal trunks of the tracheal system to stand out clearly. 

 Two main, longitudinal tracheae extend, one on each side, from 

 the above-mentioned caudal, pointed, chitinized projections to 

 the anterior region of the body, near the internal end of the 

 mouth armature, where each divides into three branches. The 

 finer details of this system have not been worked out. 



