Date of Award


Document Type

Campus Access Thesis

Degree Name

Master of Science (MS)



First Advisor

Robert Stevenson

Second Advisor

William Woods

Third Advisor

Manickam Sugumaran


Insects such as the hawkmoth, Manduca sexta, are known to exhibit several types of breathing patterns, however, explanation of the physiological mechanism and evolutionary purpose of these various breathing patterns is still debated. One breathing pattern, discontinuous gas exchange (DGC), is of special interest because in this pattern, insects exchange gases only intermittently over the course of minutes or hours. Among the numerous explanations of this punctuated breathing is the hygric hypothesis, which explains DGC as a water conserving mechanism. In order to investigate whether water loss is associated with specific breathing patterns in M. sexta pupae, I first characterized their breathing patterns, then measured water loss and gas exchange at 15°C and 27°C using flow-through respirometry. My studies revealed that three patterns of gas exchange exist in M. sexta pupae. DGC was seen more often in 15°C, while 27°C typically elicited continuous breathing patterns. Water loss patterns closely followed carbon dioxide release patterns, such that in DGC, water loss was lower and in continuous breathing, water loss was higher. The total amount of carbon dioxide released at 15°C was less than that of 27°C. These findings lend support to the hypothesis that insects may employ discontinuous breathing to control respiratory water loss and that respiratory patterns may correlated to metabolic rate.


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