90 MAINE AGRICUI.TURAL EXPERIMENT STATION. I903. 



direction. Two special channels for conveying the air to the 

 spiracles, which are situated on the ventral surface of the body, 

 have been developed. These breathing folds are grooves in the 

 integument of the ventral side, one in the thoracic region, the 

 other on the posterior part of the abdomen. The cavity of the 

 breathing folds is supplied with fine chitinous hairs and there 

 are a number of stififer hairs at the aperture of the fold which 

 serve to prevent the entrance of solid particles. There are four 

 pairs of spiracles, one abdominal and three thoracic, one pair 

 of the latter being situated just posterior to each pair of legs. 

 These spiracles open into a series of projections of the first 

 breathing folds, each fold being divided into three branches at 

 the internal end. 



The tracheal system consists of a ventral trunk on either side 

 connecting the spiracles, two dorsal girdles connecting the 

 two anterior pairs of spiracles, and a dorsal trunk on either side 

 extending from the anal spiracles to a point half way between 

 the second and third thoracic spiracles, where it joins the 

 ventral trunks. Branches are given off from the first spir- 

 acle as follows.- Two main branches, onp of which soon divides 

 into a large number of long twigs which spread out to the sides 

 of the body. The other main branch gives off the dorsal girdle, 

 and soon after divides into two about equal branches one of 

 which is the ventral trunk, while the other goes anteriorly. This 

 last trunk divides into tw^o branches, the dorsal branch breaking 

 up into long convoluted tubes which supply the sides of the 

 head, the other goes almost to the mouth opening, where it 

 curves around and breaks up into a number of branches which 

 continue anteriorly to the edge of the body. The trunks from 

 the second pair of spiracles divide into two main branches each 

 of which gives off smaller branches, the upper posteriorly and the 

 low^er anteriorly, to supply the surrounding viscera. The main 

 ventral branch goes to the ventral trunk, the dorsal branch form- 

 ing the dorsal girdle. The third spiracle opens into a trunk 

 which gives rise to an external and an internal branch. The 

 external branch soon separates into an anterior and a posterior 

 division and each of these breaks up into a number of fine 

 branches supplying the body in the metathoracic and anterior 

 abdominal region. The internal branch goes to the ventral 

 trunk. The anal spiracle gives rise to a dorsal and a ventral 



