Specificity of trail markers of forest and eastern tent caterpillars

Exploratory trails deposited on paper strips by the forest tent caterpillar (FTC),Malacosoma disstria Hubner, and the eastern tent caterpillar (ETC),M. americanum (Fabricius), as well as extracts of these trails, readily elicited interspecific trail-following behavior. In 2-choice tests involving simple Y mazes constructed from these paper strips, the caterpillars of both species preferred by approximately 31 the trails of the FTC. Studies involving whole colonies of the ETC maintained under nearnatural conditions in the laboratory, however, indicated that the trails deposited by successful foragers of the ETC as they returned to their tent from feeding sites were more attractive than the exploratory trails of either the ETC or FTC. The pronounced interspecific response of these congeners to each other's trails suggests that they utilize either qualitatively similar or identical trail-marking chemicals. Both species preferred their own trails to those ofArchips cerasivoranus (Fitch) (Tortricidae), providing the first evidence that more distantly related lepidopterous larvae utilize distinct trails.     

A chemical trail factor from the silk of the eastern tent caterpillarMalacosoma americanum (Lepidoptera: Lasiocampidae)

The leaf-feeding larvae of the eastern tent caterpillarMalacosoma americanum (Fabricius) follow silk trails laid down on branches leading from their communal tent to distant foraging sites. The response of colonies reared in the laboratory under seminatural conditions to silk trails washed in methylene chloride and to chemical trails prepared from a solvent extract of their tent or trail silk, showed that one or more soluble components of their trail is essential to the elicitation of the following response. The demonstrated ability of the caterpillars to distinguish between old and newly reinforced silk trails most likely occurs in response to a temporal change in the detectable chemical properties of their trail.     

Responses of some olfactory receptors of the eastern tent caterpillar (Malacosoma americanum) to leaves

Volatile constituents of leaves of acceptable and unacceptable plants evoke multiunit responses from the antennal olfactory sensilla of larvae of the eastern tent caterpillar. Electrophysiological investigation of the activities of three of the sixteen antennal olfactory receptors revealed that different combinations of the three responded to the various plants. In those instances where the same combination responded to more than one species of plant, the ratios of responses measured as frequency of action potentials were often different. Thus, discrimination of different plants theoretically could be based upon the absolute number of cells responding and/or the ratios of frequencies.This work was suspported by National Science Foundation grants BNS 76-02172 and BNS 78-01178.     

Identification of trail pheromone of larva of eastern tent caterpillarMalacosoma americanum (Lepidoptera: Lasiocampidae)

Previous studies have shown that larvae of the eastern tent caterpillar (Malacosoma americanum F.) mark trails, leading from their tent to feeding sites on host trees, with a pheromone secreted from the posterior tip of the abdominal sternum. 5-Cholestane-3,24-dione (1) has been identified as an active component of the trail. The larvae have a threshold sensitivity to the pheromone of 10^–11 g/mm of trail. Several related compounds elicit the trail-following response. Two other species of tent caterpillars also responded positively to the pheromone in preliminary laboratory tests.     

Synthesis of sex pheromone components of the forest tent caterpillar,Malacosoma disstria (Hübner) and of the western tent caterpillar,Malacosoma californicum (Packard)

All four geometrical isomers of 5,7-dodecadien-1-ol have been stereoselectively synthesized by using Wittig condensation reactions. (5 Z,7E)-5,7-Dodecadien-1-ol and its corresponding aldehyde are components of the sex pheromone of the forest tent caterpillar. (5 E,7 Z)-5,7-Dodecadienal is a component of the pheromone of the western tent caterpillar. These compounds have been successfully tested in the field.     

The pheromone of the eastern tent caterpillar,Malacosoma americanum (F.) (lepidoptera,Lasiocampidae)

The pheromone system of the eastern tent caterpillar,M. americanum, has been identified as a mixture of (E,Z)-5,7-dodecadienal and the corresponding alcohol. Field data on the attractiveness of the aldehyde alone were not consistent, but mixtures of aldehyde and alcohol in varying proportions were attractive to males. Addition of small amounts ofE,Z acetate toE,Z aldehyde had no effect on male response, but larger amounts reduced trap catch. Traps baited withZ,E, E,E, orZ,Z aldehydes were not more attractive than blank traps. Pherocon IC traps fortified with extra adhesive and baited with lures consisting of 500 µg (E,Z)-5,7-dodecadienal with either 250 or 100 µg of the corresponding alcohol trapped as many as 100 males/trap/night with means of 15–20. Lures prepared from purified (94%E,Z) aldehyde and alcohol were more attractive than those prepared from unpurified (58%E,Z) materials.DeceasedMention of a company name or proprietary product does not constitute an endorsement by the U.S. Department of Agriculture.     

Depletion of Host-Derived Cyanide in the Gut of the Eastern Tent Caterpillar, Malacosoma americanum

Using a colorimetric procedure, we assessed the HCN-p of black cherry leaves (Prunus serotina) ingested by the eastern tent caterpillar, Malacosoma americanum, and the cyanide content of the bolus as it passed thorough the caterpillar's digestive tract and into the detritus pool. The mean HCN-p of leaves in our study area was 1902 ± 174 (SE) ppm. Young leaves found at the tips of growing branches, which the caterpillars preferred, had a significantly higher HCN-p (3032 ± 258 ppm) than older leaves found at the middle (1542 ± 243 ppm) or base of the shoot (1131 ± 159 ppm). Following a bout of overnight feeding on young leaves, the cyanide content of the foregut and midgut boluses of early sixth-instar caterpillars averaged 631 ± 161 ppm, and 14 ± 3 ppm, respectively, indicating that host-derived cyanide is rapidly depleted as the bolus transits the gut. Some cyanide, however, remains. In three studies, the mean cyanide content of fresh fecal pellets ranged from approximately 20 to 38 ppm, while the dried, compacted pellets ranged from 63 to 85 ppm. Food in the foreguts of mature caterpillars dispersing over the ground in search of pupation sites had 417 ± 99 ppm cyanide. The potential impact of this egested and caterpillar-transported cyanide on the consumer and detritivore communities is discussed.     

Chemical marker from silk ofYponomeuta cagnagellus

Trail following in lepidopterous larvae is often attributed to chemical markers, but only a few clear-cut examples are found in the literature. In this paper evidence is presented for a chemical basis of the trail following behaviour ofYponomeuta cagnagellus. (Lepidoptera: Yponomeutidae) The marker is shown to be very persistent under laboratory conditions and is water soluble. Several possible secretory sites were investigated, and it is concluded that the marker is probably secreted together with the silk from the labial gland. Problems associated with the demonstration of trail markers in caterpillars are discussed.     

A trail pheromone from silk produced by larvae of the range caterpillarHemileuca oliviae (Lepidoptera: Saturniidae) and observations on aggregation behavior

Methylene chloride-extractable chemical(s) from range caterpillar larval silk facilitates trail-following and aggregation by early-instar larvae, but late-instar larvae are less responsive to the pheromone. Larval aggregation does not reduce water loss when larvae are exposed to low humidity, nor does aggregation prevent predation by the antFormica neoclara Emery. Grouped larvae gain weight and complete early stadia more rapidly as compared to solitary larvae. Aggregation may provide increased visibility to herbivores and increase the impact of urticating spines, thereby decreasing inadvertant predation.     

Role of trail pheromone in foraging and processionary behavior of pine processionary caterpillars Thaumetopoea pityocampa

Although caterpillars of Thaumetopoea pityocampa may mark their pathways with silk, this study shows that the material is essential to neither the elicitation nor maintenance of trail-following or processionary behavior. Trail following is dependent upon a pheromone the caterpillars deposit by brushing the ventral surfaces of the tips of their abdomens against the substrate. Earlier instars are strongly bound to their trail system; in the laboratory, caterpillars followed circular trails continuously for as long as 12 hr before breaking away from them. The trail pheromone is long-lived and soluble in nonpolar solvents, but its volatilization or degradation allows the caterpillars to distinguish new from aged trails. In contrast to trail following, processionary behavior, the head-to-tail, single-file movement of the caterpillars is dependent on neither silk nor the trail pheromone. Stimuli associated with setae found on the tip of the abdomen of the precedent caterpillar serve to hold processions together, and such stimuli take priority over those associated with either the trail pheromone or silk. Although the caterpillars discern trail strength and choose stronger over weaker trails, the trail marking system of the processionary caterpillar appears less sophisticated than those of other, previously studied species of social caterpillars, and colonies are relatively inefficient in abandoning exhausted feeding sites in favor of new food finds. In laboratory studies, females were more likely to lead processions than males, and leaders, regardless of gender, expended more energy in locomotion than followers.     

Isolation of the trail recruitment pheromone ofSolenopsis invicta

TheSolenopsis invicta trail pheromone is synthesized by the Dufour's gland and is released through the sting apparatus. The recruitment subcategory of theS. invicta trail pheromone was shown to be composed of a mixture of the orientation pheromone, (Z,E)--farnesene and an unidentified homosesquiterpene consisting of three rings and one double bond (C-1). C-1 is present in worker Dufour's glands at only 75 pg per worker equivalent. This is the first report that demonstrates that different exocrine products from the same gland control different subcategories of behavior related to mass recruitment.     

Chemical trail marking and following by caterpillars ofMalacosoma neustria

Chemical trail marking and following by gregarious caterpillars,Malacosoma neustria L. (Lepidoptera: Lasiocampidae), was studied in the laboratory. As in other species ofMalacosoma, larvae deposit a trail pheromone from a sternal secretory site when searching the host for food. Larvae in the vanguard of foraging columns establish chemical trails as they explore new territory. Marking behavior diminishes as successive unfed foragers utilize the trail. These exploratory trails are subsequently overmarked by fed larvae returning to the tent. Other foragers follow the trails of fed larvae in preference to trails of unfed larvae. Thus, like the eastern tent caterpillar,M. americanum, successful foragers ofM. neustria recruit colony-mates to feeding sites. The chemical activity of both recruitment and exploratory trails degrades slowly, suggesting that the trail pheromone ofM. neustria is a nonvolatile substance. Caterpillars ofM. neustria readily follow the nonvolatile trail pheromone which has been identified fromM. americanum, 5-cholestane-3,24-dione.     

Trail and arena marking by caterpillars ofArchips cerasivoranus (lepidoptera: Tortricidae)

The activity ofArchips cerasivoranus caterpillars is largely limited to their colonial silk web and trails. Silk pulled directly from the spinnerets of caterpillars and wound onto paper strips to form artificial trails elicited locomotion from the larvae. Trails made from extracts of silk and silk glands also elicited locomotion. These and other observations reported here indicate that the caterpillars are responsive to a water-soluble pheromone that is a component of the silk strand. Marker pheromones appear not to be secreted from other regions of the body, as has been reported for some other trail-following caterpillars.     

Significance of the pyrrolic nitrogen atom in receptor recognition ofAtta texana (Buckley) (Hymenoptera:Formicidae) trail pheromone and parapheromones

Calculations of the charge of the pyrrolic nitrogen atom in the trail pheromone ofAtta texana, methyl 4-methylpyrrole-2-carboxylate, as well as 17 analogs, showed that the most active compounds all had the same charge of –0.51 electrons on the nitrogen atom. It is suggested that the close value for this charge may be important in recognition by the receptor.This work was supported in part by the University of Iowa Computer Center.     

Chemoorientation of eastern tent caterpillars to trail pheromone, 5β-Cholestane-3,24-dione

Chemoorientation behavior of the larval eastern tent caterpillar,Malacosoma americanum, was studied using the synthetic trail pheromone 5-cholestane-3,24-dione. Divergent arms of Y mazes were treated with various concentration ratios of the pheromone. At application rates of 10^–10-10^–9 g/mm of trail, larvae showed a significant preference for stronger trails when concentration ratios differed by as little as 4:1. At application rates of 10^–8 and greater there was no significant difference in trail choice even when trails differed in strength by a full order of magnitude. Other studies showed that the caterpillars abandon the pattern of choosing stronger over weaker trails when they repeatedly fail to find food at the end of a stronger trail. Experiments in which larvae were required to choose trails separated by a gap demonstrated orientation by chemoklinotaxis. Caterpillars that had one of the maxillary palps ablated looped in the direction of their intact chemo-receptor when placed on filter paper treated uniformly with pheromone, indicating that they may also orient by tropotaxis. The relevance of these findings to the tent caterpillar communication system is discussed.     

Identification of a sex pheromone produced by female velvetbean caterpillar moth

A sex pheromone produced by female velvetbean caterpillar moths,Anticarsia gemmatalis Hübner, that attracts conspecific males was isolated and identified as a blend of (Z,Z,Z)-3,6,9-eicosatriene and (Z,Z,Z)-3,6,9-heneicosatriene in a ratio of ca. 53, respectively, when combined. The synthesized compounds elicited responses by velvetbean caterpillar moth males equivalent to those elicited by females in both laboratory wind tunnel bioassays and field trapping experiments.Lepidoptera: Noctuidae.Mention of a commercial or proprietary product does not constitute an endorsement by the USDA.Employed through a cooperative agreement between the Department of Entomology & Nematology, University of Florida, and the Insect Attractants, Behavior, and Basic Biology Research Laboratory, Gainesville, Florida 32604.     

Behavioral bioassays of termite trail pheromones

The monocyclic 14-membered ring diterpene, cembrene-A, previously identified as a nasutitermitine trail pheromone, was tested for its effectiveness as a trail pheromone inNasutitermes costalis. Artificial trails prepared from serial dilutions of racemic cembrene-A over a concentration range of 10^–1–10^–6 mg/ml were ineffective in recruiting termites. Serial dilutions of racemic cembrene-A ranging in concentration from 10^–1 to 10^–5 mg/ml produced an orientation effect. Chiral cembrene-A produced recruitment in soldiers at 10^–1 and 10^–3 mg/ml and was less ineffective in recruiting workers. Soldiers always showed a lower and more variable recruitment response to chiral cembrene-A than to sternal gland extracts. The behavioral response to both chiral and racemic cembrene-A was different in quantity and quality from that observed for sternal gland extract. Based on the results of these behavioral tests, cembrene-A appears to be a generalized nasute orientation pheromone which may show recruitment properties at unnaturally high concentrations.     

Behavioral evidence for multicomponent trail pheromone in the termite,Reticulitermes flavipes (Kollar) (Isoptera: Rhinotermitidae)

Evidence is presented for a multicomponent trail pheromone in the eastern subterranean termiteReticulitermes flavipes (Kollar). Choice tests were used to compare strength and persistency of trails made by termites in glass tubes. Tubes connected to termite nests for 24 hr were marked by termites with an extremely long-lasting chemical that persisted for at least one year, and a highly volatile substance that decayed in 15 min. Individual termites varied the trail they deposited under different circumstances. When removed from the nest and placed in a clean tube, they deposited a highly volatile substance. They left stronger and more persistent trails when exploring clean tubes attached to the nest. When they discovered a new food source, they left trails that were more attractive and far more persistent than trails made by exploring or displaced termites. A food trail made by 15 workers was still effective after 24 hr, whereas a trail made by 50 displaced workers, walking one after another through a tube, lasted only 5 min.     

Sex pheromone of the saltmarsh caterpillar moth,Estigmene acrea

Three compounds have been identified as components of the sex pheromone emitted by females of the saltmarsh caterpillar moth,Estigmene acrea (Drury). These are (Z,Z)-9,12-octadecadienal (I), (Z,Z,Z)-9,12,15-octadecatrienal (II), and (Z,Z)-3,6-cis-9,10-epoxyheneicosadiene (III). In female tip extract they were found in a ratio of 1625, respectively, and in trapped female effluvia the ratio was 1627, respectively. Combinations of III with either I or II elicited sustained upwind flight in a wind tunnel, but none of these compounds by themselves did so. There is evidence that the antennal acceptor site for III is chiral.Lepidoptera: Arctiidae.Supported in part by the Rockefeller Foundation and by National Science Foundation Grants GB-38020 and PCM 78-13241.     

Tannin sensitivity in larvae ofMalacosoma disstria (Lepidoptera): Roles of the peritrophic envelope and midgut oxidation

Final-instarMalacosoma disstria fed artificial diets containing tannic acid develop lethal pupal deformities. We examined some of the factors potentially underlying tannin sensitivity in this species, including the permeability of the peritrophic envelope to tannic acid and the chemical fate of tannic acid in the gut. Tannic acid does not penetrate the peritrophic envelope ofM. disstria, demonstrating that the containment of tannic acid within the endoperitrophic space is not sufficient to protect an insect herbivore from the adverse effects of ingested tannins. Ingested tannic acid undergoes extensive chemical modification in the midgut. Only 19–21 % of the high molecular weight components of the tannic acid ingested was recovered in the frass. Of two possible chemical fates of ingested tannic acid, oxidation is the predominant chemical transformation, whereas little hydrolysis occurs. Measurements of gut redox parameters showed that conditions in the midgut favor the oxidation of phenols. However, similar conditions occur in the midguts ofOrgyia leucostigma, in which no oxidation occurs. Therefore, oxidizing gut redox conditions do not necessarily lead to polyphenol oxidation in lepidopteran larvae. We conclude that the sensitivity ofM. disstria to ingested tannins is a consequence of their oxidation in the midgut.