Graduation Year


Graduation Month


Document Type


Degree Name

Bachelor of Arts

School or Department

Biological Sciences, Division of


Biology – Ecology and Organismal Biology

Faculty Mentor Department

Biological Sciences, Division of

Faculty Mentor

Dr. Art Woods


phasmid, insect, egg, metabolism, water loss, development

Subject Categories

Comparative and Evolutionary Physiology | Entomology


The thorny devil stick insect (Eurycantha calcarata) of New Guinea has eggs that take four months or more to develop—incredibly long for an insect. Long development times can be a challenge for eggs because of their finite resources, including nutrients, energy to support development, and water. I investigated the physiological mechanisms underlying long development times in stick insect eggs.

The first experiment examined rates of water loss and survival of eggs held in different experimental humidities (0, 75, or 100% RH). Eggs dried quickly in the 0% humidity “dry” container; and more slowly in the 75% humidity “intermediate” container. The eggs did not dry out in the 100% “saturated” container and maintained their original mass throughout the experiment. While none of the dry treatment eggs hatched, one of the intermediate treatment eggs did, and nearly all of the saturated eggs hatched. To see if the eggs could reabsorb water, they were dried until they reached 90% of their original mass. Then they were transferred into a 100% humidity or wet cotton treatment. In both cases, the eggs gained some mass, but never returned to their original mass. These experiments show that the eggs require a high humidity to survive, and that they cannot absorb water from their environment. For these eggs, water is a finite resource.

Finally, using flow-through respirometry, I measured metabolic rates of eggs during four months of development. Eggs were held in high humidity (100% RH) and their metabolic rates measured every 3 – 4 weeks. Metabolic rates were extraordinarily low early in development but increased near hatching. These data suggest that eggs delay much of their metabolism until late in development. I speculate that this delay in development is a way to keep the eggshell’s conductance to gases low, allowing the eggs to better conserve water.

Honors College Research Project


GLI Capstone Project




© Copyright 2019 Garret K. Jolma