THE OLFACTORY ORGANS OF DIPTERA 481 
THE ANTENNAL ORGANS 
Several investigators have studied the morphology of the 
antennal organs in Diptera, but since certain drawings of Hauser 
(80), vom Rath (’88), and Nagel (94) best illustrate the various 
types of antennal organs, the following discussion will be taken 
only from these three works. 
The antennae of Diptera are usually short, generally consist- 
ing of only a few segments, which bear so-called olfactory pits. 
Hr 
fad 
bgt 
53 
Figs. 50 to 55. Structure of antennal organs of Diptera; figs. 50 to 52, copied 
from Hauser (’80); figs. 53 and 54, from vom Roth (’88); and fig. 55, from Nagel 
(94). Fig. 50, longitudinal section through third or last antennal segment of 
Cyrtoneura stabulans FIll., showing internal anatomy of segment and the com- 
pound olfactory pits (C) in section. X75. The tip of the segment is not sec- 
tioned, thus showing the simple (A) and compound olfactory pits (B) from a super- 
ficial view. Fig. 51, section of a simple olfactory pit, and fig. 52, part of a section 
of a compound olfactory pit; X 750. Fig. 53, section of simple olfactory pit with 
projecting hair; X 150. Fig. 54, section of compound olfactory pit on palpus; 
100. Fig. 55, 2 olfactory hairs (Hr) on antenna of a mosquito (Culex pipiens ”); 
x 500. 
Not all of the segments bear such pits, but the distal or last one 
is usually well provided with them. Sometimes, however, ol- 
factory pits are never present on any segment, as in the mos- 
quitoes. The olfactory pits are divided into simple and com- 
