Chemical investigations of defensive steroid sequestration by the Asian snake Rhabdophis tigrinus

Rhabdophis tigrinus is an Asian natricine snake that possesses unusual defensive glands on the dorsal surface of its neck. These nuchal glands typically contain cardiotonic steroidal toxins known as bufadienolides, which are also abundant in the skin of toads. Feeding experiments demonstrated that toads consumed as prey are the ultimate sources of the bufadienolides in nuchal glands of R. tigrinus. Indeed, snakes on a toad-free Japanese island (Kinkasan, Miyagi Prefecture) lack these compounds in their nuchal glands, confirming that these snakes are unable to synthesize defensive bufadienolides. However, when snakes from Kinkasan are fed toads in the laboratory, they accumulate bufadienolides in their nuchal glands, indicating that they have not lost the ability to sequester defensive compounds from prey. In contrast, R. tigrinus from a toad-rich island (Ishima, Tokushima Prefecture) possess large quantities of bufadienolides, reflecting the abundance of toads from which these compounds can be sequestered. Feeding experiments involving gravid R. tigrinus demonstrated that bufadienolides can be provisioned to offspring so that hatchlings are chemically defended before their first toad meal. Maternal provisioning of bufadienolides can take place through two routes: by deposition in yolk and by diffusion in utero, even late in gestation. We applied bufadienolides to the surface of eggs from Kinkasan and found that the embryos are able to take up these compounds into their nuchal glands, demonstrating the feasibility of uptake across the eggshell. Female R. tigrinus provision bufadienolides to their offspring in direct proportion to their own level of chemical defense. By feeding toad-derived bufotoxins to R. tigrinus hatchlings, we determined that the sequestration of these compounds involves at least three types of modification: hydrolytic cleavage of suberylarginine side chains, hydroxylation, and epimerization.     

Nuchal glands: a novel defensive system in snakes

Of the various chemical defensive adaptations of vertebrates, nuchal glands are among the most unusual. First described in a Japanese natricine snake, Rhabdophis tigrinus, in 1935, these organs are embedded under the skin of the neck region as a series of paired glands that have neither lumina nor ducts. The major chemical components of the glandular fluid are bufadienolides, which are cardiotonic steroids also found in the skin secretion of toads. Here we review early studies of nuchal glands and briefly introduce our recent findings on the sequestration of bufadienolides from consumed toads and the maternal provisioning of those sequestered compounds. We summarize behavioral studies associated with the antipredator function of the nuchal glands, which have been conducted during our more than decade-long collaboration. Results of preliminary analyses on the possible costs of toad-eating and on the ultrastructure of the nuchal glands are also presented. Finally, we discuss the evolutionary origin of the nuchal glands and suggest future directions designed to understand the biological importance of these novel vertebrate organs, which have evolved in a limited number of snake species.     

Variation in offspring sex ratio among individual Weddell seal (<Emphasis Type="Italic">Leptonychotes weddellii</Emphasis>) females of different quality

The Trivers–Willard model predicts that in polygynous species, superior-quality females will maximize their fitness by producing male offspring. Using a sample of 1,780 Weddell seal (Leptonychotes weddellii) pups recorded over 31 years, we investigated relationships between offspring sex ratio and maternal age, reproductive experience, an index of maternal lifetime reproductive output, and annual environmental variations. We found evidence that females with higher index of lifetime reproductive output were more likely to produce male than female offspring but found only weak evidence that large-scale environmental variations influenced sex ratios. Our results suggest that mothers manipulate offspring sex to maximize their own fitness, and inherent maternal quality may influence offspring sex. These findings support the Trivers–Willard sex-allocation model. Electronic supplementary material  The online version of this article (doi:) contains supplementary material, which is available to authorized users.     

Inter-specific variation in anti-predator behavior in sympatric species of kangaroo rat

Kangaroo rats, Dipodomys, occupy desert habitats with little cover and thus are under high predation risk from diverse predators. The behavior used to assess predation risk or to escape capture is unknown. We therefore compared anti-predator behavior of two sympatric species of kangaroo rat of different sizes, D. merriami and D. spectabilis. We first examined whether kangaroo rats use olfaction as a first line of defense against snake predation and tested the rats for their responses to scent extracted from two species of snake that live sympatrically with the kangaroo rats, the Mojave rattlesnake (Crotalus scutulatus) and the gopher snake (Pitophis melanoleucus). We also tested for species differences in anti-predator behavior through 15-min interactions between the kangaroo rats and free-moving gopher snakes. We found that D. spectabilis actively approached the scent of both rattlesnakes and gopher snakes more than controls of vegetable oil and evaporated solvent (Fig. 1). In contrast, D. merriami did not differentiate snake odors from controls in the experimental arena, but they sniffed the sand where a free-moving snake had passed more than D. spectabilis. Both species successfully avoided predation in encounters with live snakes. Although total numbers of approaches and withdrawals were similar (Fig. 2), D. spectabilis spent significantly more time within striking distance of the snake than D. merriami. D. spectabilis approached the head of the snake in 93% of its approaches and often engaged in nose to snout contact with the snake. If the snake struck, D. spectabilis jumped directly backward to avoid a strike and footdrummed at a safe distance. In contrast, D. merriami oriented to the snake more than D. spectabilis, but approached the head in only 41% of the approaches and rarely engaged in nose-to-snout contact. The snakes struck, hissed and decreased predatory approaches with D. spectabilis but not with D. merriami (Fig. 3). These results show that kangaroo rats can behaviorally influence the risk of being preyed on by snakes. The two species differ, however, in how they react to snakes. The larger D. spectabilis confronts snakes while the smaller D. merriami monitors snakes from a safe distance and avoids them.     

Factors influencing length of maternal care in brown bears (<Emphasis Type="Italic">Ursus arctos</Emphasis>) and its effect on offspring

Length of maternal care, i.e. the interval between successfully raised litters, is the most important factor explaining the variation in reproductive rate among brown-bear (Ursus arctos) populations. In this paper, we examine the variation in length of maternal care in radio-marked brown bears and its effect on their offspring in northern Sweden. Young stayed with their mothers for 1.4–1.5 or 2.4–2.5 (in one case 3.5) years and were weaned with body masses varying from 17 to 69 kg. The probability of yearling litters staying with their mother for a 2nd year increased with decreasing yearling body mass, and was higher for litters with two offspring than for litters with one or three to four offspring. Staying with their mothers for a 2nd year had a positive effect on mass gain in yearlings and this effect was more pronounced in litters with two than three to four offspring. Body mass of 2-year-olds was not related to age of weaning, suggesting that keeping offspring for an additional year mainly compensated for low yearling body mass. If large offspring body mass positively affects later offspring survival and reproduction, mothers may be able to optimize the length of maternal care according to the litter size and the size of their yearlings.Communicated by F. Trillmich     

Structure and function of the eversible glands of the aquatic firefly <Emphasis Type="Italic">Luciola leii</Emphasis> (Coleoptera: Lampyridae)

Summary. When attacked or otherwise disturbed, larvae of the aquatic firefly Luciola leii display fork-shaped glands laterally from the meso- and metathorax as well as each abdominal segment. Glandular eversion is accompanied by a strong pine oil-like odour, thanatosis and glowing from paired larval light organs. Observations by SEM and TEM revealed that there are numerous, almost spherical protuberances, measuring 9 μm in diameter on the surface of each gland. Each protuberance is connected to a well developed secretory cell via a 0.1 μm thick and 0.2 μm long stalk and bears three to six 7 μm long spines on its apex. The convoluted glandular walls measure 0.2 μm. The cytoplasm of the secretory cells is characterized by the presence of numerous mitochondria and an extensive system of cisternae and tubular endoplasmic reticulum. Preliminary GC-MS analysis of the glandular secretion revealed two volatile terpenoids: terpinolene and γ-terpinene. Choice and no-choice bioassays involving fish and ants as well as other predators demonstrate that the secretions serve as an effective deterrent against a range of ecologically relevant enemies. The larval postural adjustments, light emission, everted glands, and glandular release of distasteful or repellent compounds, appear to function as a multi-modal, aposematic larval defence. The tandem evolution of glandular secretions and conspicuousness in larval fireflies could partially explain their successful radiation into both aquatic and terrestrial habitats.     

Identification of trail pheromone compounds from the labial glands of the stingless bee Geotrigona mombuca

Foragers of several species of stingless bees deposit pheromone spots in the vegetation to guide recruited nestmates to a rich food source. Recent studies have shown that Trigona and Scaptotrigona workers secrete these pheromones from their labial glands. An earlier report stated that species within the genus Geotrigona use citral from their mandibular glands for scent marking. Since convincing experimental proof for this conjecture is lacking, we studied the glandular origin of the trail pheromone of Geotrigona mombuca. In field bioassays, newly recruited bees were diverted by artificial scent trails that branched off from the natural scent trail deposited by their nestmates only when they were baited with extracts from the foragers’ labial glands. Compounds extracted from the mandibular glands, however, did not release trail following behavior. This demonstrates that the trail pheromone of G. mombuca is produced in the labial glands, as in Trigona and Scaptotrigona. Furthermore, in chemical analyses citral was identified exclusively in the foragers’ mandibular glands, which disproves its supposed role as a trail pheromone. The labial glands contained a series of terpene- and wax type esters, with farnesyl butanoate as major constituent. We, therefore, postulate that the trail pheromone of G. mombuca is composed of a blend of esters.     

Heterospecific call recognition and phonotaxis in the orientation behavior of the marbled newt,Triturus marmoratus

The role of acoustic cues as reference cues for orientation by amphibians has been demonstrated in anurans, the only amphibian group that engages in acoustic communication, but not in urodeles. Orientation responses of marbled newts, Triturus marmoratus, were studied to determine whether heterospecific calls elicited positive phonotaxis. The orientation tests consisted in presenting either a familiar acoustic stimulus, the advertisement calls of natterjack toads (Bufo calamita), or a control stimulus, the advertisement calls of European green toads (Bufo viridis) that the newts would not be expected to recognize. Marbled newts and natterjack toads occur in simpatry, but T. marmoratus and B. viridis are allopatric species. Thus, T. marmoratus is distributed over the northern half of the Iberian Peninsula, whereas B. viridis occurs in the Balearic Islands, but not over the Iberian Peninsula. Newts were released in a circular arena while a recorded chorus of natterjack toads or European green toads played outside the arena to determine whether they displayed positive phonotactic orientation. Our results show that marbled newts performed positive phonotaxis when exposed to the breeding calls of natterjack toads, but not to those of European green toads. Newts chose a compass course in the direction of the advertisement calls of B. calamita. Acoustic information might improve orientation accuracy. This study is the first to provide evidence of heterospecific call recognition and positive phonotactic response in urodeles.Communicated by W. Wiltschko     

Territorial counter-singing in male sac-winged bats (<Emphasis Type="Italic">Saccopteryx bilineata</Emphasis>): low-frequency songs trigger a stronger response

In many animal species, individuals compete for resources but avoid escalated conflicts by threat displays, i.e. a mutual signalling behaviour that enables the opponents to predict the outcome of the conflict without the necessity of actual fighting. For example, territory holders may use acoustic signals to communicate not only their own identity and the borders of their territory but also their competitive quality, fighting ability and motivation. Here, we show that male sac-winged bats, Saccopteryx bilineata, adjust their vocal territorial displays according to the fundamental frequency of territorial songs of their opponents. In playback experiments with territorial males, low-frequency stimuli elicited a higher territorial song rate and length than high-frequency stimuli. Male S. bilineata that sing more often and with lower fundamental frequencies have been shown to sire more offspring than their competitors. Fundamental frequency of territorial songs, hence, may reveal male quality and, consequently, the resulting threat posed to competing males. We argue that this is reflected in the increased response of competitors to low-frequency territorial songs shown here. Such competitive signalling behaviour has been shown in a few mammal species like red deer and baboons but, thus far, not in bats. Electronic supplementary material  The online version of this article (doi:) contains supplementary material, which is available to authorized users.     

Identification and biological activity of sex pheromone components from females of the plum moth Illiberis rotundata Jordan (Lepidoptera: Zygaenidae: Procridinae)

The plum moth, Illiberis rotundata Jordan (Lepidoptera: Zygaenidae: Procridinae), is a pest of orchards in Japan and China. Few chemical ecological studies have been directed towards the Zygaenidae and particularly the Procridinae. To investigate the sex pheromone of this species, extracts of pheromone glands from adult female I. rotundata were analyzed by coupled gas chromatography-electroantennography (GC-EAG) and coupled gas chromatography-mass spectrometry (GC-MS). Whilst GC-EAG on male moths showed an active peak, identified as 2-butyl (7Z)-dodecenoate, GC-MS also revealed the presence of the homologue 2-butyl (9Z)-tetradecenoate. Electroantennographic investigations, as well as field tests, strongly suggested the natural compounds to have the (R)-configuration at the stereogenic centre. Field results demonstrate 0.2 mg of a 1:1-mixture of (2R)-butyl (7Z)-dodecenoate and (2R)-butyl (9Z)-tetradecenoate to be a powerful lure that may be used in pest control measures against I. rotundata. The chemical structures of the new pheromone components show the same features as those of other zygaenid species: unsaturated fatty acids esterified with a short chain chiral alcohol. This is the first example of a two-component blend constituting the pheromone of a procridinid species.     

Preservation and loss of the honey bee (<Emphasis Type="Italic">Apis</Emphasis>) egg-marking signal across evolutionary time

Honey bee workers are able to distinguish queen-laid eggs from worker-laid eggs, and remove (‘police’) worker-laid eggs. The cue that police workers use is as yet unidentified but is likely to be a chemical signal. This signal benefits queens for it ensures their reproductive monopoly. It also benefits collective workers because it allows them to raise more closely related queen-laid males than the less-related sons of half sisters. Because both parties benefit from the egg-marking signal, it should be stable over evolutionary time. We show that Apis mellifera workers can distinguish queen-laid from worker-laid eggs of the dwarf honey bee A. florea, a phylogenetically distant species that diverged from the A. mellifera lineage 6–10 mya. However, A. mellifera workers are unable to distinguish worker-laid eggs of A. cerana, a much more recent divergence (2–3 mya). The apparent change in the egg-marking signal used by A. cerana may be associated with the high rates of ovary activation in this species.     

Temporal accumulation of phenylpropanoids in male fruit flies, <Emphasis Type="Italic">Bactrocera dorsalis</Emphasis> and <Emphasis Type="Italic">B. carambolae</Emphasis> (Diptera: Tephritidae) following methyl eugenol consumption

Summary. Males of dacine tephritids, Bactrocera carambolae and B. dorsalis are strongly attracted to, and compulsively feed on methyl eugenol (ME), a potent attractant for many Bactrocera species. While ME was shown to be biotransformed into phenylpropanoids, 2-allyl-4,5-dimethoxyphenol and (E)-coniferyl alcohol, and temporarily stored in the rectal gland of male B. dorsalis prior to release during courtship at dusk, B. carambolae male produces only the latter compound along with its de novo synthesized pheromone components. Both species were also shown to have different age-related response, sensitivity and consumption levels of ME. Here, we monitored and compared temporal changes in the accumulation profiles of these phenylpropanoids by the two sibling species, with male rectal glands being individually excised at different time intervals from 15 minutes to 20 days after initial ME feeding and analysed quantitatively. Results are discussed in light of plant-fruit fly co-evolution relationship.     

Nursing of own and foster offspring by Utah prairie dogs (<Emphasis Type="Italic">Cynomys parvidens</Emphasis>)

From 1995 through 2005, I studied nursing among Utah prairie dogs (Cynomys parvidens) living under natural conditions at Bryce Canyon National Park, UT, USA. I observed 850 aboveground nursings, which involved 122 mothers and 248 juveniles from 134 litters. Most of the mothers that nursed aboveground were middle-aged, and most nursing juveniles had been coming aboveground for 1–3 weeks. Most nursings involved a single juvenile, lasted 1–10 min, and occurred between 1800 hours and 2000 hours. Seventy-five percent of nursings (598/796) involved a mother suckling her own juvenile offspring; the other 24.9% (198/796) involved a mother suckling another mother’s offspring (i.e., communal nursing). Communal nursings involved juveniles of the home territory, and many communal nursings (74/198 = 37.4%) involved close kin such as half-siblings, grandoffspring, full-nieces, and full-nephews; other communal nursings (37/198 = 18.7%) involved more distant kin such as full-second cousins and full-third cousins. Of seven hypotheses that might explain the evolution of communal nursing, evidence supports the importance of two: elevated inclusive fitness via indirect selection and communal nursing as a cost of coloniality.     

Pursuit-deterrent communication between prey animals and timber rattlesnakes (Crotalus horridus): the response of snakes to harassment displays

A thorough understanding of communication requires an evaluation of both the signaler and receiver. Most analyses of prey–predator communication are incomplete because they examine only the behavior of the prey. Predators in these systems may be understudied because they are perceived as less tractable research subjects, due to their more cryptic hunting behaviors and secretive lifestyles. For example, research on interactions between rodents and rattlesnakes has focused on the behavior of rodent signalers, while responses of snakes have been virtually unexamined. Rattlesnakes are ambush predators, and capture rodents by waiting at foraging sites for long periods of time. In this study, I take advantage of the sedentary nature of this foraging strategy and use fixed videography to record natural encounters between timber rattlesnakes (Crotalus horridus) and their prey. Three different prey species were found to exhibit conspicuous visual displays to snakes, both when snakes were actively foraging, and when they were basking. After receiving displays, foraging snakes left their ambush sites and moved long distances before locating subsequent ambush sites, indicating that they responded to displays by abandoning attempts to ambush prey in the vicinity of signalers. This study represents the first quantitative analysis of the response of free-ranging snakes to signals from their prey, and elucidates a technique by which such quantitative data can be more easily obtained.     

Genetic evidence for monogamy in the cooperatively breeding red-cockaded woodpecker

We examined the genetic relationship among putative parents, offspring, and helpers in 224 red-cockaded woodpeckers (Picoides borealis) from the Sandhills of North Carolina. Comparison of DNA similarity with a pedigree constructed from 3,823 individually-marked birds observed from 1979 to 1992 provided verification of observed relatedness in the sampled population (R ² = 0.87,df = 14,P<0.001). In this population, breeding pairs may or may not have helpers, most of which are males that remain on their natal territory. Our sample included helpers assisting their parents, helpers assisting a related male and an unrelated female, and helpers assisting an unrelated pair. Band by band comparison and examination of similarity among DNA profiles indicated that all offspring from non-helped nests were sired by their putative parents (n = 28 families). Similarly, all but one offspring in helped nests were also sired by their putative parents (n = 16 families). In the exceptional case, the offspring evidently was sired by a male external to the group. Analysis of similarity values supported the conclusion that matings by helpers or extra-group males are rare or non-existent. Our results indicate that in this species advantages gained by individuals remaining on their natal territories as helpers do not generally include siring offspring. Correspondence to: S. Haig     

Weaning in the guinea pig (<Emphasis Type="Italic">Cavia aperea</Emphasis> f. <Emphasis Type="Italic">porcellus</Emphasis>): Who decides and by what measure?

Offspring should be selected to influence maternal effort to maximize their own fitness, whereas mothers are selected to limit investment in present progeny. In mammals, this leads to a conflict over the amount of milk provided and the timing of weaning. The intensity and time course of such conflict has so far mostly been investigated experimentally in altricial rodents. However, it is expected that offspring options for conflict will depend on developmental state. We therefore investigated in the highly precocial domestic guinea pig (Cavia aperea f. porcellus) who decides over nursing performance and weaning and how pup state influences these decisions. Specifically, we tested whether a threshold mass of pups predicts weaning time. By exchanging older litters against neonates and vice versa, we produced a situation in which females differed in lactational stage from the cross-fostered pups. Our results indicate that females decide about the timing of weaning, as cross-fostered younger pups were weaned at a much younger age than controls and older pups benefited from continuing lactation of foster mothers. Growth rates did not differ in the treatment groups, and different weaning ages resulted in differing weaning mass refuting the hypothesis that weaning is based on a threshold mass of offspring. This constitutes clear evidence that in a precocial rodent, the guinea pig, decisions about maternal care are primarily determined by maternal state and little influenced by pup state despite the extreme precociality of offspring. We suggest that precocial pups show little resistance to early weaning when food is abundant, as they reach sufficient nutritional independence by the middle of lactation to enable independent survival.     

Why do female Belding's ground squirrels disperse away from food resources?

We examined the effects of food provisioning on the natal dispersal behavior of Belding's ground squirrels (Spermophilus beldingi). We provided extra food to adult and yearling females in their maternal territories during pregnancy and lactation, and to offspring of these females in their natal areas for 6 weeks after weaning. We used unprovisioned young of unprovisioned mothers as controls. Provisioning influenced the probability of dispersal from the natal area by female but not male S. beldingi. All surviving male S.␣beldingi dispersed by 55 weeks of age, regardless of whether they and their mothers received extra food. By contrast, we observed a significant trend, beginning 3 weeks after weaning and continuing through the yearling year, for a greater proportion of provisioned than control female S. beldingi to emigrate from the natal area. Competition for food did not appear to influence natal dispersal of females. However, overall population density, density of females weaning litters, and rates of aggression and vigilance among these females, were higher in provisioned than control areas, suggesting that competition for non-food resources was unusually intense in provisioned areas. We propose that juvenile female, but not juvenile male, S. beldingi may emigrate from the natal site to increase access to areas with low densities of conspecifics. Together with findings of earlier workers, our results suggest that spatial and temporal distributions of environmental resources are important influences on the dispersal behavior of female ground squirrels. Received: 28 February 1996 / Accepted after revision: 16 October 1996     

GC-EAD responses to semiochemicals by eight beetles in the subcortical community associated with Monterey pine trees in coastal California: similarities and disparities across three trophic levels

Summary.  Antennae of six sympatric bark and ambrosia beetles (Scolytidae), Dendroctonus valens LeConte, Gnathotrichus retusus (LeConte), Hylastes tenuis Eichhoff, Ips mexicanus (Hopkins), Ips plastographus maritimus Lanier, and Pseudohylesinus sericeus (Mannerheim), and two scolytid predators, Enoclerus sphegeus (F.) (Cleridae) and Lascontonus tuberculatus Kraus (Colydiidae), were analyzed by gas chromatographic-electroantennographic detection (GC-EAD) for their responses to synthetic Ips spp. pheromone components, and host and nonhost volatiles. The beetles emerged from cut logs of pitch canker-infected Monterey pine trees, Pinus radiata D. Don. There were significant disparities in EAD response patterns to the hemiterpene and monoterpene alcohol pheromone components that are typically produced by Ips spp. Antennae of I. p. maritimus responded strongly to ( ± )-ipsdienol, ( ± )-ipsenol, amitinol, and lanierone; antennae of I. mexicanus responded strongly to (1S,2S)-(–)-cis-verbenol, with weaker responses to ( ± )-ipsdienol, ( ± )-ipsenol, and amitinol; antennae of H. tenuis responded to (1S, 2R)-(–)-trans-ver-benol, with less pronounced responses to (–)-cis-verbenol and 2-methyl-3-buten-2-ol; and antennae of D. valens, G. retusus, and P. sericeus generally responded to all Ips spp. pheromone components except 2-methyl-3-buten-2-ol (D. valens and G. retusus) and E-myrcenol (G. retusus and P. sericeus). Ips mexicanus responded only to the (–)-enantiomers of ipsenol and ipsdienol, whereas I. p. maritimus responded to (–)-ipsenol, but to both the (+)- and (–)-enantiomers of ipsdienol. The antennae of the two predaceous insects (E. sphegeus and L. tuberculatus) responded to a range of the Ips spp. pheromone components. Host monoterpenes elicited no antennal responses from E. sphegeus, G. retusus, H. tenuis, and I. mexicanus, but several monoterpenes elicited various levels of responses from D. valens and I. p. maritimus antennae. Interestingly, antennae of female D. valens responded to (–), but not (+)-limonene. α- and β-Pinene elicited weak responses from L. tuberculatus antennae. EAD responses to selected nonhost volatiles were almost identical among the six scolytid species, with trans-conophthorin eliciting the strongest response in most cases, followed by three C₆- alcohols and two C₈-alcohols. The antennal responses by most of these species to linalool or geranylacetone were very weak; (E)-2-hexenal, (Z)-3-hexenyl acetate, and benzyl alcohol elicited almost no response. The response pattern of P. sericeus to nonhost volatiles differed slightly from the rest of the scolytids: a strong response to linalool, weaker response to the C₈-alcohols. The two predaceous Coleoptera generally had weak, but detectable, responses to nonhost volatiles, except for a relatively strong response to trans-conophthorin by L. tuberculatus. No notable differences in EAD responses were observed between males and females of the two Ips spp. Our results provide an electrophysiological baseline for future efforts to identify attractive and repellent semiochemicals (aggregation pheromones, host kairomones, or nonhost interruptants) for this guild of scolytids and their key predators that are associated with moribund and pitch canker- infected P. radiata.     

The effects of larval experience with a complex plant latex on subsequent feeding and oviposition by the cabbage looper moth: Trichoplusia ni (Lepidoptera: Noctuidae)

Summary. Leaf disc choice and oviposition bioassays were used to examine the effects of larval experience with a Hoodia gordonii latex on subsequent behaviors. The latex deterred feeding and oviposition by “naïve” cabbage looper (Trichoplusia ni, Noctuidae) larvae and moths with no previous exposure to the material. “Experienced” insects, reared on a diet with the H. gordonii latex (1000 ppm), exhibited lesser feeding deterrence relative to naïve insects. Experienced female moths actually preferred to lay eggs on treated rather than control leaves. There was no observed transfer of behavioral preferences from experienced parents to their offspring. Our results suggest that moths may be acquiring oviposition preferences from larval feeding experience as described by Hopkins’ host selection principal (HHSP) or through chemical legacy.     

The trail pheromone of the ant <Emphasis Type="Italic">Crematogaster castanea</Emphasis>

Summary. The major component of the trail pheromone of the myrmicine ant Crematogaster castanea has been identified as (R)-2-dodecanol from the tibial glands of the hind legs. The substance gave activity comparable to the contents of 8 tibial glands at a concentration of 1 pg per 32 cm trail.