94 EN TOMOLOGY 
The thoracic ganglia govern the appendages of their respec- 
tive segments. These ganglia and those of the abdomen are 
to a great extent independent of brain control, each of these 
ganglia being an individual motor center for its particular 
segment. Thus decapitated insects are still able to breathe, 
walk or fly, and often retain for several days some power of 
movement. 
In regard to the sympathetic system, it has been shown ex- 
perimentally that the frontal ganglion controls the swallowing 
movements and exerts through the stomatogastric nerve a 
regulative action upon digestion. The dorsal sympathetic sys- 
tem controls the dorsal vessel and the salivary glands, while 
the ventral sympathetic system is concerned with the spiracu- 
lar muscles. 
5. SENSE ORGANS 
For the reception of sensory impressions from the external 
world, the armor-like integument of insects is modified in a 
great variety of ways. Though sense organs of one kind or 
another may occur on almost any part of an insect, they are 
most numerous and varied upon the head and its appendages, 
particularly the antenne. 
Antennal Sensilla.—Some idea of the diversity of form 
in antennal sense organs may be obtained from Figs. 116-125, 
taken from a recent paper by Schenk, whose useful classifica- 
tion of antennal sensilla, or sense organs, is here outlined: 
1. Sensillum ceeloconicum—a conical or peg-like projection 
immersed in a pit (Figs. 116-117). In all probability 
olfactory. 
2. S. basiconicum—a cone projecting above the general sur- 
face (Fig. 118). Probably olfactory. 
3. S. styloconicum—a terminal tooth or peg seated upon a 
more or less conical base (Fig. t19). Olfactory. 
4. S. cheticum—a bristle-like sense organ (Fig. 120). 
Mactile: 
5. 9. trichodeum 
Tactile: 
a hair-like sense organ (Figs. 121, 122). 
