20 Journal New York Entomological Society. t VuL xxvu. 



Anatomy of the Orthoptera, Hymenoptera and Neuroptera, and Miall 

 and Denny (1886) on the cockroach. Packard (1878-1880) has 

 given an excellent general description of the tracheal system of the 

 red legged locust (Melanoplus femur-rubrum DeG.), but his work 

 is lacking in detail, and contains many inaccuracies, due no doubt to 

 the fact that the dissecting microscopes available at that time were 

 but crude implements in comparison with the perfected binoculars of 

 to-day and even with the help of our improved appliances and tech- 

 nique, the tracing out of the various ramifications of the tracheal 

 system requires much time and patience. Snodgrass (1903) has 

 apparently described the general features of the tracheal system in 

 Dissostcira, but his paper is not accessible to me and but few copies 

 of it were ever printed. Therefore, since no detailed account of 

 the respiratory system of any primitive insect is at present generally 

 available, the morphology of the tracheal system of Dissostcira has 

 been worked out in the present paper to fill this lack. 



Organs of Respiration. 

 A. External Organs or Spiracles. (Plate III, Fig. 4.) 



Ten pairs of spiracles are present in Dissostcira Carolina, two 

 pairs of which are located on the sides of the thorax and eight pairs 

 on the abdomen. 



I. Situation. (Plate III, Fig. 4.) 



The first thoracic spiracle (I) lies in the lateral intersegmental 

 membranous region connecting the pro- and meso-thorax, and be- 

 neath the hind lobe of the pronotum. 



The second thoracic spiracle (77) is situated just above the sec- 

 ond coxal cavity between the meso- and meta-thorax. 



The first abdominal spiracle (HI) lies in the auditory cavity just 

 anterior to the tympanal sense organ. The other seven pairs of 

 abdominal spiracles (IV to X) are all similarly placed on the lower 

 anterior margin of each dorsal plate to the ninth abdominal segment 

 where no spiracles are present. 



II. Morphology. 



In the Carolina locust three types of spiracles are found. 

 (a) First Thoracic Spiracle. — (Plate IV, Fig. 11.) This is by far 

 the largest spiracle in the body and is closed externally by a large 



