Gall induction by hemipteroid insects

Abstract

The Thysanoptera and sternorrhynchous Hemiptera induce galls through feeding action, a behavior similar to that in the Cecidomyiidae. Salivary glands of gall-founding female thrips include greater quantities of hydrolyzing enzymes and soluble proteins than those in either males or pupae, which possibly alter the host-tissue metabolism, enabling galls to develop. Piercing-and-sucking mouthparts of the Hemiptera are adapted for an exclusively liquid diet – either the plant sap from vascular elements or the fluids from living nonvascular cells. Hemipteran-salivary chemistry alters the hormonal balance in the host, triggering gall development. Soluble proteins in the saliva of nymphs are critical. Gall-inducing Hemiptera vigorously take oxygen from the ‘gall’ tissue, which triggers auxin activity. Gall-inducing behaviors in the Thysanoptera and Sternorrhyncha are similar in that gall induction occurs by the feeding action of a single female, and gall-founding females disperse over short distances seeking young host-plant organs. Besides providing a comparative overview of gall induction by hemipteroids, this paper highlights the subtle but noteworthy differences in behaviors among these insects, thus offering pointers to their evolution within the specialist guild of herbivory.

¹To Warren Gene Abrahamson III (Bucknell University, Lewisburg, PA, USA), who blazed new trails in interpreting the evolutionary ecology of galls and inducing insects. Memories of my stay in his laboratory in 1990–1991 are pleasant.

Keywords:

• Hemiptera
• physiology of galls
• saliva
• Sternorrhyncha
• Thysanoptera
• mouth parts

Acknowledgements

Daniel Burckhardt (Naturhistorishes Museum, Basel, Switzerland), Roman Rakitov (Paleontological Institute, The Russian Academy of Sciences, Moscow, Russia), Carl Schaefer (University of Connecticut, Storrs, Connecticut, USA), and Dietrich Werner (Universität zu Köln, Köln, Germany) reviewed the prefinal draft. I am grateful to Carl, Daniel, Dietrich, and Roman. Rakitov kindly supplied I.D. Mitjaev's 1968 paper, enabled with an English summary of Mitjaev's findings. Werner supplied me his papers on gall-inducing Tingidae. Both Roman and Dietrich were admirably rapid in their responses to my requests; I thank them for that help.

Notes

¹To Warren Gene Abrahamson III (Bucknell University, Lewisburg, PA, USA), who blazed new trails in interpreting the evolutionary ecology of galls and inducing insects. Memories of my stay in his laboratory in 1990–1991 are pleasant.