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Table 1.

Comparison of rates of CO2 emission from the anterior mesothoracic spiracle and the posterior subelytral spiracles ofCircellium bacchus during continuous sampling from either outside or inside the subelytral cavity

Absolute rate of CO2 emission (μl h-1)
From inside the SEC
From outside the SEC
Beetle numberMass (g)Mesothoracic spiraclesSubelytral spiraclesA:P ratioMesothoracic spiraclesElytral caseA:P ratio
8.012 56.29 187.98 1:3.3 — —  
7.122 3.94 288.92 1:73.3 289.31 52.29 5.5:1 
8.539 1.83 224.0 1:122.4 428.06 60.05 7.1:1 
3.94 0.82 211.63 1:257.3 116.88 39.65 3.0:1 
4.238 6.17 115.19 1:18.6 106.5 28.06 3.8:1 
9.79 7.9 669.36 1:84.7 195.39 46.68 4.0:1 
Absolute rate of CO2 emission (μl h-1)
From inside the SEC
From outside the SEC
Beetle numberMass (g)Mesothoracic spiraclesSubelytral spiraclesA:P ratioMesothoracic spiraclesElytral caseA:P ratio
8.012 56.29 187.98 1:3.3 — —  
7.122 3.94 288.92 1:73.3 289.31 52.29 5.5:1 
8.539 1.83 224.0 1:122.4 428.06 60.05 7.1:1 
3.94 0.82 211.63 1:257.3 116.88 39.65 3.0:1 
4.238 6.17 115.19 1:18.6 106.5 28.06 3.8:1 
9.79 7.9 669.36 1:84.7 195.39 46.68 4.0:1 

A, anterior mesothoracic spiracle; P, posterior subelytral spiracle; SEC,subelytral cavity; —, no measurement taken.

Readings from six individuals are shown to illustrate that CO2is normally expired from the mesothoracic spiracle unless it is experimentally removed from the subelytral cavity. Readings from outside the elytral case were taken on individuals that had elytral holes resealed with dental wax. Slight leakage from these holes might account for the relatively high levels of CO2 measured here.

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