Salivary surprise: Symmerista caterpillars anoint petioles with red saliva after clipping leaves

• DOI: 10.1371/journal.pone.0265490
• Publication Date: 2022-03-16T17:45:51Z
• Authors: David E. Dussourd
• Keywords: Petiole (insect anatomy)

After feeding on a tree leaf, caterpillars in ten families sever the petiole and allow remaining leaf fragment to fall ground. Previous researchers proposed that thereby reduced bird predation by eliminating visual evidence of feeding. In this study, 26 species five were filmed clipping leaves. Caterpillar behavior did not conform cue hypothesis. Some clipped midribs petioles repeatedly even though single clip would suffice reduce cues for birds. Every caterpillar rubbed its spinneret (which secretes saliva from labial glands) over or midrib stub. notodontids Symmerista albifrons S . leucitys , stubs bathed red fluid. Cauterizing eliminated fluid application. Dissections documented anterior portion their glands contained pigment, confirming secretion is saliva. When applied stubs, pigment travelled several mm minutes within xylem demonstrating potential rapid movement salivary constituents into plant. diverse caterpillars, including leaves, contains substances reported suppress plant defenses. Thus, likely functions primarily remove cues, but introduce prevent defenses being mobilized nearby leaves where feeds next.