Larval Aggregation of Heortia vitessoides Moore (Lepidoptera: Crambidae) and Evidence of Horizontal Transfer of Avermectin

Abstract

Aquilaria sinensis (Lour.) Gilg is an economically important tree species that produce the highly prized agarwood. In recent years, agarwood production has been seriously threatened by the outbreak of Heortia vitessoides Moore, a leaf-eating pest that shows gregariousness during the larval stage. However, little attention has been paid to the aggregation behavior of H. vitessoides larvae. In the present study, we collected 102 cohorts of H. vitessoides larvae (13,173 individuals in total) in the wild; 54 cohorts were comprised of the same-instar larvae, and 48 cohorts were comprised of larvae with different developmental stages (instars). In general, young larvae (<third instar) tended to form large aggregations, whereas older-instar larvae were either solitary or formed small aggregations. Laboratory studies showed a strong aggregation tendency in the newly hatched and second-instar larvae of H. vitessoides, whenever the individuals originated from the same or different sibling cohorts. In addition, all newly hatched larvae died within two days after they were isolated. When newly hatched larvae were initially assigned in 10-larvae cohorts (containing sibling individuals) or 20-larvae cohorts (either containing individuals originating from the same or different sibling cohorts), their larval survivorship, duration of larval stage, and adult emergence were not significantly different. Interestingly, combining avermectin-treated larvae (donors) with untreated ones (receptors) significantly decreased larval survivorship and adult emergence of receptors, indicating a horizontal transfer of avermectin among H. vitessoides larvae. This study enhances our understanding of the population ecology of H. vitessoides, and may bring novel insights into the management strategies against this pest.

Lethal, transmission, behavioral, and physiological effects of Metarhizium anisopliae against gregarious larvae of Heortia vitessoides and synergistic effects between Metarhizium anisopliae and insecticides

“…Here we separated donors and receptors because the mark on the donors would disappear within 1-2 days due to molting, and therefore the donors and receptors cannot be distinguished. 14 Each concentration for each M. anisopliae strain was repeated ten times. The survivorship of donors and receptors was recorded each of the 9 days.…”

“…2.5 Experiment 3: effects of Metarhizium anisopliae on the aggregation tendency of Heortia vitessoides larvae Methods provided by Liang et al 14 were modified to investigate whether M. anisopliae conidia influence the aggregation tendency of H. vitessoides larvae. In brief, 20 A. sinensis leaves were evenly pasted onto the bottom of each 2000 mL plastic container using double-faced adhesive tapes (Deli®, Ningbo, China), and each leaf was fully contacted with the adjacent leaves (Fig.…”

Developmental niche construction in necrophagous larval societies: Feeding facilitation can offset the costs of low ambient temperature

“…Aggregation usually sits in‐between these two niche construction strategies: group formation most often involves both relocation (to join or follow a group) and perturbation of the local environment by the group (Costa et al, 2006). For instance, social caterpillars, cockroaches as well as woodlice can actively create groups (relocation; Jeanson et al, 2005; Devigne et al, 2011; Liang et al, 2019) that modify the selection pressures faced by the group members (perturbation), for example, by reducing water and/or heat loss (Broly et al, 2014; Klok & Chown, 1999; Yoder & Grojean, 1997).…”

Chromosomal-Level Reference Genome of the Moth Heortia Vitessoides (Lepidoptera: Crambidae), A Major Pest of Agarwood-Producing Trees

“…vitessoides is recognised as the most destructive pest of the lign aloes A. malaccensis and A. sinensis in Malaysia and southern China, respectively [50,81]. During its larval stages, the first to third instars aggregate and feed on leaves of Aquilaria species, while the older instars tend to be solitary ( [50], Fig. 1).…”