THE ORGANS OP RESPIRATION. ItvJ 



Kirby and Spence describe large lateral spiracles in the bugs, lying 

 between the meso- and meta-thorax, but I could perceive in our bugs 

 (Pentatoma rujipes and P. hce,morrlioidalis) depressions only at these 

 parts ; but if the acute posterior margin of the prosternum, which lies 

 precisely in this cavity, be removed, the spiracle is observed very dis- 

 tinctly beneath it. In Belostoma a very distinct spiracle is found at 

 the posterior margin of the pleura, consequently between the meta- 

 thorax and the abdomen, which, however, appears to belong to the 

 first abdominal segment, because in the bugs the spiracles lie always in 

 the ventral segments themselves, and, indeed, at the exterior margin 

 of the ventral plates, and not, as in the beetles, beneath the wings and 

 the elytra. 



The Neuroptera alone, of the remaining orders, have a distinctly 

 separated pro-thorax; it is here therefore that we must notice them. 

 Semblis displays two distinct pairs (PL XIV. No. 3. f. 2. 4. a and /3,) 

 of spiracles in the thorax, the first between the pro- and meso-thorax, 

 and the second between the meso- and meta-thorax. Whether there 

 be a third pair between the meta-thorax and the abdomen I could not 

 clearly perceive either here or in Myrmecoleon, but in the dry speci- 

 mens examined by me there appeared to be incisions. The two first 

 pairs lie, also in the ant-lion, exactly in the same place. Panorpa dis- 

 plays two pairs of spiracles in the thorax and five pairs in the abdo- 

 men ; the two first lie between the pro- and meso-thorax, and between 

 the latter and the meta-thorax, and display themselves as small brown 

 points. In the abdomen they are placed, as in all Neuroptera, in the 

 connecting membrane of each pair of segments, closely in front of that 

 to which they belong. 



In the Dictyotoptera, as those most closely allied to the preceding 

 order, with the exception of the Libellula? and Termites, they are, from 

 their minuteness, difficult to investigate. The Libcllu/ce have two pairs 

 of spiracles in the thorax, one pair being between the pro- and meso- 

 thorax, each of which, however, is covered by a small scale originating at 

 the posterior margin of the pronotum ; the second pair is seated between 

 the meso- and meta-thorax, at the sides of the thorax. The former are 

 long, somewhat bent incisions ; the latter very small, ovate, two-lipped 

 spiracles. I have observed none between the meta-thorax and the 

 abdomen. It has also been said that they have no abdominal spi- 

 racles. But Reaumur and Sprengel admitted their existence in those 



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