1929] 
Tracheal System of Blepharipa scutellata 
221 
observed tracheal endings, the conclusion that these endings 
indicate the position of the spiracles seems warranted. 
(Fig. 1). 
At the posterior end of the body are two fairly heavy 
chitinous rings marking the edges of the spiracles. In 
each of these, covering the spiracle openings, are chitinous 
plates which vary in their thickness. I was unable to see 
any openings through these plates. Greene, describing 
puparia of muscoid flies, (1921), states that “each plate 
has two or more openings for respiration, and these open- 
ings are called “slits;” Snodgrass (1924) describes the open- 
ings in the stigmatic plates of Rhagoletis. 
Just beneath the stigmatic plate is the stigmatic chamber. 
The walls of this chamber are slightly thicker than the 
tracheal walls to which they are joined, and they are some- 
what pigmented. Upon drying a reddish, rusty-looking 
deposit appeared on the walls and upon the interior surface 
of the stigmatic plate. 
No lateral spiracles are observable on the larva. 
Parkard (1874) in a short table of spiracular positions 
says that the larvae of Cecidomyiidae have nine pairs ; one 
prothoracic, and eight abdominal, and that Muscidae have 
two pairs, one prothoracic, and one on the ninth abdominal 
segment. Further (1898), he says that the number of pairs 
varies in larval Diptera in adaptation to their varied modes 
of life. 
Pratt (1897) figures an embryo of Melophagus ovinus 
(Linn) with a row of ten small circles inside of each of 
wdiich is a smaller circle, which he designates as “Tracheal 
invaginations.” Williams (1910) states that the larva of 
Cecidomyia resinicoloides Williams (Cecidomyiidae) has 
nine pairs of spiracles, “one on the first thoracic segment 
and one each on segments 4-11.” 
Snodgrass (1924) says that eight pairs of spiracles 
appear on the puparium of Rhagoletis, and he cites various 
authors to the effect that the lateral spiracles in larvae of 
the higher Diptera are present as imaginal discs. 
It would appear, therefore, that in the higher Diptera the 
lateral spiracles are not absent, but remain in an un- 
developed state until they take part in the formation of the 
