The size relationship between insects and their hosts

Abstract.

• 1 Regressions of adult insect size on host size were tested. The analysis was restricted to highly host-specific insects that had thus been exposed to a narrow range of host size.
• 2 The phylogenetic regression method was used to analyse the data, so as to allow for the possible phylogenetic effects in cross-species data.
• 3 Significant positive regressions were found in all the groups tested: female flower thrips, Meligethes species of pollen beetle, tephritid flies, and male and female fleas. They were also found by standard regressions within. and between Actornithophilus species of bird louse.
• 4 The regression of thrips size on pollen size was not significant, providing evidence against a hypothesis involving food size.
• 5 The regression of flea body size on host hair/feather length was significant, which is consistent with a hypothesis involving the size of spaces on the host.
• 6 The relationships may have implications for the understanding of evolutionary host shifts.