• Bottom-up effect;
  • hypersensitive reaction;
  • induced defences;
  • insect galls;
  • insect–plant interactions;
  • plant module size


1. Hypersensitive reaction is an important type of induced defence by which the plant elicits a defence response to pathogens and insects. Hypersensitive reaction has been argued to be the most common plant resistance mechanism against insect herbivores that have intimate associations with their host plants.

2. The work reported here attempted to establish how important and widespread hypersensitive reaction might be against gall-forming species across host taxa.

3. Hypersensitive reaction was the most important mortality factor against gall formation across host plant taxa in seven out of eight cases.

4. The number of insect galls correlated with the size of the leaves but module (leaf) size was a weak factor influencing the incidence of plant hypersensitive reaction to galling.

5. Insect galls and hypersensitive reactions occurred in genetically distant as well as geographically widespread host plant taxa.