Volatiles from male honeydew excretions attract conspecific male spotted lanternflies, Lycorma delicatula (Hemiptera: Fulgoridae)

Abstract

The spotted lanternfly (SLF), Lycorma delicatula (Hemiptera: Fulgoridae), is a generalist phloem feeder that produces copious amounts of honeydew, which in turn coats the understory. These insects form large aggregations covering the trunks of some trees, while similar trees nearby mysteriously seem unattractive. We investigated whether volatiles from SLF honeydew are attractive to conspecifics by collecting honeydew from the field and testing it for SLF attraction in a two-choice olfactometer. We found that honeydew excreted by adult male SLF was significantly attractive to male SLF, but not female SLF. Although the honeydew excreted by adult female SLF did not significantly attract male or female SLF, both sexes showed a positive trend towards attraction in response to female honeydew in the olfactometer. Analysis of the headspace volatiles of honeydew was conducted, and numerous semiochemicals were identified. Five of which, 2-heptanone, 2-octanone, 2-nonanone, benzyl acetate, and 1-nonanol, were tested in two-choice behavioral assays against a blank control. Benzyl acetate and 2-octanone were attractive to both sexes, whereas 2-heptanone was only attractive to males, and 2-nonanone only to females. The remaining compound, 1-nonanol, repelled females, but not males. Although honeydew has been reported as a source of kairomones for some natural enemies, this may be the first report of sex-specific attractants for conspecific insects found in the honeydew volatiles of a planthopper.

Factors Guiding the Orientation of Nymphal Spotted Lanternfly, Lycorma delicatula

“…Only the first instars prioritized higher SLF density over larger trees. Whether SLF moved to trees with higher background populations of SLF on them because the SLF were producing attractive signals (i.e., pheromones, substrate vibrations, or damage kairomones) [ 28 , 29 , 30 ], or because there was something initially more attractive about those trees (i.e., kairomones, visual cues, or nutritional quality) [ 9 , 31 ], which consequently lured both the marked and wild SLF, could not be ruled out from this experiment. However, the fact that tree size is also strongly attractive and correlated to SLF density suggests that there could be a positive feedback loop in which SLF may initially be attracted to larger trees, and once groups of SLF find those trees, the combination of the larger trees and signals from SLF may result in more SLF attraction.…”

“…A possible signal that might be detected from the ground could be honeydew falling onto surfaces beneath infested trees. Adult male SLF orient to the volatiles from conspecific honeydew [ 28 ], so it is possible that nymphs also communicate through signals derived from their honeydew, facilitating aggregation or location of suitable host plants. Host volatiles, or kairomones, released by host plants have been shown to be attractive to SLF both in the laboratory and field [ 9 , 33 ].…”

“…The insects themselves could emit chemical signals such as pheromones that also could indicate the presence of conspecifics and facilitate aggregation. Evidence that pheromones may exist in SLF honeydew and body volatiles has been reported for adults as a possible mechanism for observed aggregation behavior and for mate location [ 28 , 29 ], and aggregation in SLF nymphs could also be mediated by pheromones. The first evidence of pheromones in the suborder Auchenorrhyncha, to which fulgorids belong, was recently reported [ 48 ], and pheromones have been documented in the two other major hemipteran suborders Heteroptera (true bugs) [ 49 , 50 ] and Sternorrhynca (aphids, whiteflies, psyllids, scales) [ 51 , 52 , 53 , 54 ].…”

“…Although the possibility of nutritional differences between host plants has been proposed [ 25 ], other factors are likely involved in SLF arriving or arresting on one host over another and thus should be considered. Possible mechanisms driving this phenomenon could involve semiochemicals such as kairomones from host plants [ 9 ] or semiochemicals from SLF honeydew exudates [ 28 ], pheromones [ 29 ], vibroacoustic signals [ 30 ], visual cues [ 31 , 32 ], or some combination thereof. Despite attraction to the kairomone methyl salicylate in both laboratory and field experiments [ 33 ], numerous other kairomones that were attractive in the laboratory [ 9 ] were not attractive in the field (MFC, unpublished data) [ 34 ], and methyl salicylate also yielded inconsistent field results [ 35 ], suggesting that yet unknown factors may compete with the efficacy of those semiochemical lures in the field.…”

The subapical labial sensory organ of spotted lanternfly Lycorma delicatula

“…14: 230438 chemical classes, including acids, alcohols, aldehydes, esters, ketones, lactones, phenolics and terpenes. Several of these odorants were previously identified in SLF host plants and honeydew and have been shown to be behaviourally active in laboratory bioassays [6,7,13].…”