He teaches and carries out research on insect development and physiology. He became interested in glowworms around 2000 when he decided to take some students on a night field trip to view them in rainforest at night. He regularly visits the world’s most famous glowworm site—Waitomo Glowworm Cave in New Zealand—where he advises the environmental advisory group on glowworm population monitoring. David teaches a number of courses, mostly on entomology, the study of insects. Beside bioluminescence and biological rhythms, his research interests include the developmental biology of insects and the structure and function of insect glands and sense organs.