A. J. Grove 
19 
stout nerve is given off which extends in the median line to the 
posterior end of the body. There it expands into a fairly large 
ganglion from which nerves are given off, which, from their position, 
must pass to the muscles which control the anal and reproductive 
apertures. Also nerves are given off from the main trunk during its 
passage from the median abdominal ganglion to the posterior abdominal 
ganglion. These nerves are given off fairly regularly in pairs and pass 
to the segments of the abdomen. 
Text Fig. 12 is a camera lucida drawing of a dissection showing 
this abdominal nerve and the posterior abdominal ganglion with the 
nerves they give off. In addition to this abdominal nerve, two small 
nerves are given off from the median abdominal ganglion one on either 
side of the above-mentioned nerve, and it is to be inferred from their 
course that they pass to the viscera. 
The Tracheal System. 
The tracheal system almost completely eluded the efforts of the 
early investigators like Dufour to figure it with anything approaching 
completeness. 
From the literature I have been able to obtain, it seems that 
Witlaczil was among the first to give illustrations of the respiratory 
apparatus of Aphides. He figures the tracheal system of Aphis 
pelargonii (1882), and also indicates the general tracheal system of 
a Goccid, and the apterous stage of Chermes abietis and Phylloxera 
quercus (1886). The results I have obtained agree very largely with 
his representation of Aphis pelargonii. Flogel (1904 and 1905) also 
describes the tracheal system of the winged female of Aphis ribis, but 
no figures are given. 
Notwithstanding the small size and somewhat sedentary habit of 
the Aphis in this stage of its life history, the tracheal system is 
developed to a remarkable degree (Text Figs. 13 and 14). 
Situated along the sides of the body are nine pairs of stigmata— 
two pairs being thoracic and the remaining seven abdominal. The first 
pair is placed in the posterior margin of the first thoracic segment, and 
the second pair on the anterior margin of the third thoracic segment. 
The second thoracic segment is entirely destitute of stigmata. The 
seven pairs of abdominal stigmata are situated—one pair in each—in 
the first seven segments of the abdomen. The tracheal system is 
composed of well-defined dorsal and ventral systems—a short trachea 
2—2 
