THE HALTERES OF THE BLOW-FLY. 615 
having a purely mechanical function, producing currents of 
air, or limiting the excursions of the wing; (4) organs of 
hearing; and (5) organs of equilibration, balancers. 
Historical and Critical—Gleichen [8], in 1764, thought them 
to be analogous to drumsticks, which produce the hum of the 
insect by striking the great wing scales; and Landois [281] 
held that their vibrations set in motion a portion of the 
spiracular valve, which he termed the ‘ Brum-ring,’ Neither 
of these views are tenable, and have received little, if any, 
support. 
Braxton Hicks, in 1856-57, thought their function olfactory ; 
and Loew [293], discarding Hicks’s view, suggested that they 
assist in respiration, by producing currents of air in the vicinity 
of the metathoracic spiracle. These views are not only un- 
supported by evidence, but are quite inconsistent with the 
results of direct experiments ; and it may be remarked, in 
relation to Loew’s theory, that the result of their vibration 
would be immaterial as compared with the currents of air pro- 
duced by the movements of the wings; further, if I am right 
in my contention that carbon dioxide is not excreted from the 
spiracles, such currents are unnecessary for the respiration of 
the insect. 
Jousset de Bellesme, in entire ignorance of the complexity and 
minute structure of the halteres, supposes that they act as 
stops to the wings ; he regards them as stiff pegs which check 
the backward and downward movement of the wing by acting 
on what he terms the axillary areolus. His brochure is a 
record of some apparently carefully carried out experiments, 
one of which, if it can be credited, is of the highest interest, as 
he states that insects deprived of the balancers have the power 
of flight restored if a tail of horse-hair several centimetres long 
is glued on to the extremity of the abdomen. Whether this 
observation is correct or not, the conclusions of Jousset do not 
appear to me to be justified by his facts, and a theory which 
entirely ignores the great complexity of the halteres and their 
gigantic sensory nerves, great ganglia and sensory nerve endings, 
cannot be accepted as satisfactory. 
