Aposematism in Archips cerasivoranus not linked to the sequestration of host-derived cyanide.

This study addressed the question of how caterpillars of Archips cerasivoranus feeding upon Prunus virginiana cope with the cyanogenic compounds of their food. Analysis by ion chromatography showed that young and aged leaves of P. virginiana consumed by the caterpillars during spring have hydrogen cyanide potentials (HCN-ps) of 2,473 +/- 130 ppm and 1,058 +/- 98 ppm, respectively. Although less than 3% of the cyanide released as the caterpillars feed escapes into the atmosphere, the larva's bright-yellow aposematic coloration and conspicuous activity can not be attributed to the sequestration of cyanide. Only six of 25 samples of the caterpillars' defensive regurgitants collected from 12 field colonies contained cyanide (17.6 +/- 6.54 ppm), less than 5% of the quantity previously reported to occur in the regurgitant of the tent caterpillar M. americanum. Only seven of 13 caterpillars assayed had detectable quantities of cyanide in their bodies (3.9 +/- 0.9 ppm). The fecal pellets that encase the cocoon contained no cyanide, nor did the frass that litters the leaf shelters. The small quantities of cyanide that occur in the caterpillar compared to the HCN-p of ingested plant material appear attributable to paced bouts of feeding and the maintenance of a highly alkaline foregut that inhibits cyanogenesis.

REVIEW paper: mare reproductive loss syndrome.

An epidemic of early fetal loss (EFL), late fetal loss (LFL), fibrinous pericarditis, and unilateral uveitis which occurred during the spring of 2001, are together now known as the mare reproductive loss syndrome (MRLS). A similar epidemic with less intensity was reported during the same period of time from southern Ohio, West Virginia, and Tennessee. The same syndrome with lesser intensity recurred in 2002. The estimated economic loss from the syndrome in 2001 and 2002 together was approximately $500 million. Both EFL and LFL were characterized by the absence of specific clinical signs in aborting mares. Nonhemolytic Streptococcus spp. and Actinobacillus spp. accounted for 65% of the organisms isolated from fetuses submitted for a postmortem during the MRLS period in 2001 and 2002. The pathologic findings in fetoplacental units of LFL included bronchopneumonia and funisitis, and there were no findings in EFL. Epidemiologic studies conducted in 2001 suggested an association between the presences of eastern tent caterpillars (ETC) in pastures with MRLS. Experimental studies in pregnant mares by exposure to ETC, or administration by stomach tube or with feed material, reproduced EFL and LFL. Similar experimental studies in mouse, rats, and goats with ETC were unsuccessful. Currently, 2 hypotheses are proposed for MRLS. One hypothesis proposes that an ETC-related toxin with secondary opportunistic bacterial invasion of the fetus leads to MRLS. The second hypothesis suggests that a breach of gastrointestinal mucosal integrity by hairs of ETC leads to a bacteremia and results in MRLS. In 2004, a similar equine abortion storm was reported from Australia and caterpillar exposure was identified as a risk factor for the abortion. In 2006, the syndrome was observed in Florida and New Jersey.

Larvae of the fall webworm, Hyphantria cunea, inhibit cyanogenesis in Prunus serotina.

The larvae of the fall webworm, Hyphantria cunea (Dru.), though vulnerable to cyanide poisoning, consume the cyanogenic leaves of black cherry, Prunus serotina, without apparent harm. The cyanide contents of leaves, defensive regurgitant, the bolus, and frass were assayed by ion chromatography to determine the fate of the toxin in the caterpillar. Leaves collected in September, when the caterpillars were feeding, contained 1592+/-276 p.p.m. cyanide. Samples of dried frass obtained from caterpillars fed these leaves yielded 2868+/-552 p.p.m. cyanide. Frass extracted directly in NaOH yielded approximately five percent of the cyanide obtained from frass ground in buffer and distilled in Warburg flasks, indicating that cyanogenesis is largely inhibited as the bolus traverses the gut. This inhibition is attributable to the ability of the caterpillar to maintain a foregut environment in the presence of the bolus that is sufficiently alkaline to suppress the conversion of the plant cyanogen to cyanide. Although a number of caterpillars feed without harm on cyanogenic plants, this it the first shown to inhibit cyanogenesis in this manner.

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

Although caterpillars of Thaumetopoea pityocamnpa 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 substate. 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.

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.

Developments in social terminology: semantic battles in a conceptual war.

The problems posed by the evolution of the diverse forms of animal sociality are among the most important and fascinating in evolutionary biology. The conceptual and terminological framework guiding studies of social evolution has been based on a particular insect model, namely, that of highly derived family-structured societies. Virtually all other social systems have been categorized as 'less social' relative to these societies. Recently, the ambiguities and constraints inherent in this hierarchical classification have led to numerous proposals to amend social terminology. What is the best framework for studying social evolution? Should the traditional classification be expanded, narrowed or abandoned altogether? In an important respect, most recent proposals present the same wine in a different bottle by retaining and recasting key terms of the traditional social-evolutionary classification.

Trail following and recruitment: Response of eastern tent caterpillarMalacosoma americanum to 5ß-cholestane-3,24-dione and 5ß-cholestan-3-one.

Studies were conducted to determine the relative effectiveness of 5ß-cholestane-3,24-dione (diketone) and 5ß-cholestan-3-one (monoketone) in eliciting trail following from eastern tent caterpillars,Malacosoma americanum. In Y maze tests, trails prepared from the monoketone were followed preferentially over diketone trails, even when the diketone trail was several orders of magnitude stronger. Under field conditions, colonies readily abandoned well-developed trail systems in favor of artificial trails that were established with the monoketone. Other tests in which the caterpillars selected trails prepared from the monoketone (but not the diketone) more often than their own recruitment trails indicate that the monoketone constitutes the chemical basis of recruitment communication in this insect. The study also shows that tent caterpillars are highly sensitive to small differences in the amount of monoketone in a trail and can distinguish between new and aged trails prepared from the compound.

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.

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

Chemoorientation behavior of the larval eastern tent caterpillar,Malacosoma americanum, was studied using the synthetic trail pheromone 5ß-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.

Daily foraging schedule of field colonies of the eastern tent caterpillar Malacosoma americanum.

The daily foraging patterns of seven colonies of the eastern tent caterpillar, Malacosoma americanum, were monitored photoelectronically during the last three larval stadia to provide the first detailed record of the foraging behavior of a gregarious caterpillar under field conditions. Colonies were active an average of 49.3% of each day. Three bouts of foraging, centered about 0600 h, 1500 h and 2000 h (EST), occurred daily during the fourth and fifth stadia. Although ambient temperatures were less favorable for foraging and food processing than at other times of the day, the caterpillars were most active at dusk and dawn, and spent comparatively little time away from the tent during the daylight hours. In the last (sixth) stadium, the caterpillars foraged only under the cover of darkness. A lack of relationship between the rate at which the caterpillars processed food and the spacing of their feeding bouts, indicates that this species follows a schedule of feeding and growth shaped by factors other than those directly related to feeding efficiency and ambient temperature. Colony foraging patterns may reduce caterpillar mortality by minimizing contact between larvae and day-active predators and parasitiods.

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. 5ß-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.

Site of secretion of the trail marker of the eastern tent caterpillar.

A new site of secretion of a chemical trail marker was found on the sternum at the tip of the last abdominal segment of the larva of the eastern tent caterpillarMalacosoma americanum. Larvae marked from this site by drawing their sterna along the substrate when they extended existing trails in search of food and again when they established recruitment trails to food-finds. Differences in the quantity or quality of the marker deposited by exploring and recruiting caterpillars may account for the greater activity of the recruitment trails.

Trail marking by larvae of the eastern tent caterpillar.

Eastern tent caterpillars that are successful foragers deposit trails as they return to the tent that are more attractive than the exploratory trails of the unfed larvae. The trails of these fed returning larvae attract unfed tentmates to food finds anre chemical factors account for the attractiveness of these trails.