SQUIRT-GUN DEFENSE IN BURSERA AND THE CHRYSOMELID COUNTERPLOY

I determined the impact of resins canals of Bursera schlechtendalii on the growth and survival of its specialized vein-cutting beetle Blepha rida sp. nov. Bursera schlechtendalii produces terpenes stored under p ressure in networks of canals that run throughout the cortex of the st em and in the leaves. When a leaf is broken, it releases abundant resi ns, which may bathe the leaf surface and often form a squirt that trav els for up to 150 cm. Plants vary in the proportion of their leaves th at release resins after damage. Larvae of the chrysomelid genus Blepha rida can inflict substantial damage to plants because they avoid the s quirt response by cutting the leaf veins before consuming the leaves. Nevertheless, resins still protect plants against this insect. Both na turally occurring and experimentally placed larvae had higher mortalit y on highly responsive plants. Young larvae became mired in secretions after rupturing the canals and died. Also, on highly responsive plant s larvae spent more time cutting veins and grew more slowly. Thus, whi le the squirt response of Bursera is not a completely effective defens e, it imposes a handling-time cost on larvae, reduces their growth rat e, and increases their mortality.