VISUAL STIMULI INFLUENCING ORIENTATION BY LARVAL GYPSY MOTH,LYMANTRIA DISPAR(L.)

Abstract

In laboratory and field experiments involving artificial and real tree trunks, all larval instars of gypsy moth [Lymantria dispar (L.)] crawling on a horizontal surface were influenced by the diameter, height, and species of a tree. For most larval instars, black artificial tree trunks were preferred to white trunks. The influence of the diameter and height of a host on larval attraction was examined with cardboard columns. The degree of larval attraction to a column of a certain diameter and height was positively correlated with the angle at which the column was presented. Significantly more larvae were attracted to bolts of red oak (Quercus rubra L.) than to white birch (Betula papyrifera Marsh.) or trembling aspen (Populus tremuloides Michx.). The implications of these findings and their possible effects on host colonization are discussed.

Influence of burlap-band colour on larval, pupal, and egg-mass counts of Lymantria dispar (Lepidoptera: Lymantriidae)

“…The results show that burlap colour affects the choice of resting and pupation sites by gypsy moth larvae and the subsequent deposition of egg masses by emerging female gypsy moths. As with previous research where gypsy moth larvae demonstrated a strong affinity for black over white trunks (Roden et al 1992), gypsy moth larvae in this study also showed a stronger affinity for black burlap than lighter coloured tan bands. Although the underlying reason(s) behind the selection of dark objects by gypsy moth remains unclear, plausible hypotheses explaining this behaviour have been developed.…”

“…The movement of migrating gypsy moth larvae and their selection of artificial tree bands as shelters is more complex than previously reported. Knowledge that gypsy moth larvae are affected by the colour of burlap, the species, diameter, and height of a host (Roden et al 1992), that burlap bands decrease the movement of larval gypsy moth from trees (Liebhold et al 1986), and that the number of larvae under a band is affected by weather (Weseloh 1987) all argue for the adoption of standards for the use of burlap bands for monitoring gypsy moth populations. Adoption of such standards, such as black bands placed at DBH, would remove variables that confound results between studies and would make comparisons between different studies more useful.…”

“…The influence of the colour of the material used to construct artificial shelters and the effect it may have on larval preference, however, has not been investigated. Gypsy moth larvae are highly attracted to darker colours, particularly black (Roden et al 1992). Furthermore, the attraction to darker trunks by all larval instars is stronger than the attraction to a preferred foliage (Smitley et al 1993).…”

Sensitivity of seven clones of poplar to the attack by caterpillars of Gypsy moth (Lymantria dispar L.) and fungus Pollacia elegans (Vuill.) Fabr

“…This may be linked to aging of the leaves, where the content of tannin increases during vegetation (Feeny, 1970) and the leaves turn darker. Gypsy moth caterpillars are more attracted to a darker than a lighter trunk, and to trunks that are wider in diameter, which was determined by using plastic modules for trunk simulation (Roden et al,1992). Although the sense of sight helps caterpillars locate the trees or herbaceous plants, it is still not developed enough to have a crucial role in recognition of plants, which is supported by the fact that the process is carried out in complete darkness (Schoonhoven, 1973).…”

Effects of plant chemical extracts and physical characteristics of Apium graveolens and Chenopodium murale on host choice by Spodoptera exigua larvae

“…Several plant characteristics have been shown to be important factors in host acceptance by lepidopterous larvae. Such characteristics include plant phenology (Scriber & Slansky, 1981), nitrogen content (White, 1984), water content (Scriber & Slansky, 1981), defensive chemicals (Ehrlich & Raven, 1964), and physical characteristics of the plant (Roden et al, 1992). For example, leaf toughness has been shown to reduce the suitability of plant materials for herbivores in several ways including increased time and energy expenditure (Rausher, 1981) and dilution of nutritious plant parts with non-nutrient forms such as lignin and cellulose (Coley, 1983).…”