Comparative study of the defensive behavior and morphology of the gland opening area among harvestmen (Arachnida, Opiliones, Gonyleptidae) under a phylogenetic perspective

The arachnids of the order Opiliones (harvestmen) have a pair of scent glands opening at the sides of the body, the substances of which are used in defense. Several types of behavioral, morphological and chemical defensive mechanisms have been assigned to the order as a whole, although some of these tactics were restricted to particular groups. Only around 25 species have been studied from this perspective so far. In the present paper, we analyzed 33 species (mostly from the largest harvestmen family, the Gonyleptidae) aiming at recognizing the usefulness of the defensive characters in taxonomy and evolutionary biology. We observed the morphology of the gland opening (ozopore) area and the defensive behavior, and their relationship, and mapped these traits on an available phylogenetic hypothesis of relationship within Gonyleptidae. As outgroups, we analyzed Cosmetidae and Stygnidae. Combining the observed behavioral characters of the emission of defensive secretion (near the ozopore, with liquid displacement through an integumentary groove, or in form of a jet) with the morphological types of the gland opening (direction of the integumentary dome that surrounds the gland opening, presence of two openings and the relationship between their sizes, and presence of a V-shaped cut at the anterior opening), we recognized eight patterns. In addition, we could examine the evolution of such traits within Gonyleptidae.     

Chemical and behavioral defenses of the neotropical harvestman Camarana flavipalpi (Arachnida: Opiliones)

The defensive secretion of the harvestman Camarana flavipalpi (Gonyleptidae) was chemically characterized, revealing the presence of a single, highly volatile component (2-methyl-5-ethyl-phenol). Individuals do not frequently use chemical defenses and rely mainly on thanatosis as defense. Two types of emission of secretions were recorded: a globule at the gland opening without liquid displacement and liquid displacement along the lateral margins of the dorsal scute with accumulation of fluid at the lateroposterior area of the body. The anterior opening of the ozopore is covered by an integumentary dome that faces the laterodorsal area of the scute. The lateral channel is well defined near the opening of the ozopore and along the lateral margin of the dorsal scute as rows of small granules. The ozopore morphology of C. flavipalpi is similar to closely related species and simplified when compared with other species that promptly release chemical secretions.     

The ecological tale of Gonyleptidae (Arachnida,Opiliones) evolution: phylogeny of a Neotropical lineage of armoured harvestmen using ecological,behavioural and chemical characters

The large Neotropical family Gonyleptidae comprises nearly 820 species divided into 16 subfamilies. The majority of publications on harvestman ecology, behaviour and scent gland secretion chemistry have focused on this family. We used the information available in the literature and combined it with an intensive search for ecological, behavioural and chemical data to infer the phylogeny of the Gonyleptidae. We included 28 species belonging to 14 of the 16 gonyleptid subfamilies in the ingroup and four species belonging to the families Cosmetidae, Stygnidae and Manaosbiidae in the outgroup. We performed the analyses using equally weighted characters and coded 63 characters comprising 153 states, which makes this the largest non‐morphological, non‐molecular phylogenetic data matrix published to date. We obtained five most parsimonious trees, and the strict consensus resulted in six collapsed nodes. The results show that the monophyly of Gonyleptidae is equivocal because Metasarcinae is placed at a basal polytomy with the outgroups Cosmetidae and Stygnidae. Gonyleptinae, Pachylinae and Progonyleptoidellinae are polyphyletic groups, but the remaining subfamilies are monophyletic and have several synapomorphies. Based on the resulting topology, we discuss the performance of ecological, behavioural and chemical characters, and map a selected set of characters to discuss their evolutionary patterns in the family.     

Interspecific variation in the microanatomy of cosmetid harvestmen (Arachnida,Opiliones, Laniatores)

Scanning electron microscopy (SEM) is a useful tool for identifying interspecific variation in often overlooked structures that may represent useful sources for informative phylogenetic characters. In this study, we used SEM to compare the morphology of 12 cosmetid species from Central America, the Caribbean, and North America including multiple species for the genera Cynorta, Erginulus, and Paecilaema. To determine if microanatomical structures were unique to the cosmetid taxa under examination, we investigated the microanatomical structures of six additional species of gonyleptoidean harvestmen representing the families Agoristenidae, Cranaidae, Gonyleptidae, Manaosbiidae, and Stygnidae. Our results indicate that the shape of the ocularium (narrow, intermediate, or broad) did not vary within cosmetid genera, whereas the morphology of the rough pit glands on the eye mound varied considerably between species. Each cosmetid species had 10–20 rough pit glands on the ocularium whereas only the eye mounds of Avima intermedia (Agoristenidae) and Glysterus sp. (Gonyleptidae) had similar structures. With regards to the surface texture of the dorsal scutum, cosmetid harvestmen exhibited a rivulose‐microgranulate morphology (6 species), a microtuberculate‐rivulose‐microrgranulate morphology (4 species), or a microgranulate morphology (2 species). In contrast, each of the gonyleptoidean species exhibited a microgranulate pattern, with the exception of Stygnoplus clavotibialis, which had a rivulose‐microgranulate surface texture. For cosmetid harvestmen, we observed considerable interspecific variation in the shape and number of teeth on the fixed and moveable fingers of the male chelicerae. Similarly, we also observed interspecific variation in the distribution and shape of tubercles on the ventral and dorsal surfaces of the femur of the pedipalp. Overall, our results indicate that there are several microanatomical structures associated with the ocularium, dorsal scutum, male chelicera, and pedipalp that could represent informative phylogenetic characters in future taxonomic studies of cosmetid harvestmen. J. Morphol. 275:1386–1405, 2014. © 2014 Wiley Periodicals, Inc.     

A comparative analysis of the chemical nature of defensive secretions of Gonyleptidae (Arachnida: Opiliones: Laniatores)

The arachnids of the order Opiliones (harvestmen) produce substances used in defense. In the present paper, we analyzed 22 species of Gonyleptidae to explore the use of defensive substances in taxonomy and evolutionary biology. Thirty-seven different compounds were detected, 18 of which were preliminarily identified. These compounds were mapped onto a phylogenetic tree showing the relationships within the Gonyleptidae. Data from Cosmetidae were used as an outgroup. Five ketones and six alkyl phenols were reported for the first time in harvestmen.     

Walk it off: predictive power of appendicular characters toward inference of higher‐level relationships in Laniatores (Arachnida: Opiliones)

Morphological characters are essential for establishing phylogenetic relationships, delimiting higher‐level taxa, and testing phylogenetic relationships inferred from molecular sequence data. In cases where relationships between large clades remain unresolved, it becomes imperative to establish which character systems are sound predictors of phylogenetic signal. In the case of Laniatores, the largest suborder of Opiliones, some superfamilial relationships remain unresolved or unsupported, and traditionally employed phenotypic characters are typically of utility only at the family level. Here we investigated a promising set of morphological characters that can be discretized and scored in all Opiliones: cuticular structures of the distal podomeres (metatarsi and tarsi). We intensively sampled members of all known families of Laniatores, and define here three new, discrete appendicular characters toward refinement of Laniatores superfamilial systematics: metatarsal paired slits (MPS; occurring in all Laniatores except Sandokanidae), proximal tarsomeric gland (PTG; in Icaleptidae, Fissiphalliidae, and Zalmoxidae), and tarsal aggregate pores (TAP; found in Gonyleptoidea, Epedanoidea, and Pyramidopidae). We conducted statistical tests on each character to characterize the strength of phylogenetic signal and assess character independence, based on alternative tree topologies of Laniatores. All three characters had high retention indices and bore significantly strong phylogenetic signal. Excepting one pairwise comparison, morphological characters did not evolve in a correlated manner, indicating that appendicular morphology does not constitute a single character system. Our results demonstrate the predictive power and utility of appendicular characters in Opiliones phylogeny, and proffer a promising source of diagnostic synapomorphies for delimiting superfamilies.     

Fissiphalliidae, a new family of South American laniatorean harvestmen (Arachnida: Opiliones)

Fissiphalliidae, a new family of the Opiliones suborder Laniatores, is described in the superfamily Gonyleptoidea, based on a new genus (Fissiphallius n. gen.) und 3 new species (F. sturmi n. sp., F. spinulatus n. sp., F. sympatricus n. sp.) from Colombia. Most emphasized are the male genitalic characters, unique in Opiliones: A honzontally split truncus which results in a long movable (glans) and an immovable finger (distal part of the truncus). Both hide the extremely long stylus with the seminal opening at its end. In an expanded state, the movable finger is bent dorsally by an erectile vesicle. It is shown that male genitalic characters in Opiliones display clear functional and constructional traits on the family level. Those characters, if used appropriately, will demonstrate that several families in gonyleptoid Laniatores are polyphyletic and should be divided into several taxa of the family level.     

Ultrastructure of chemoreceptive tarsal sensilla in an armored harvestman and evidence of olfaction across Laniatores (Arachnida,Opiliones)

Harvestmen (Arachnida, Opiliones) are especially dependent on chemical cues and are often regarded as animals that rely mainly on contact chemoreception. Information on harvestman sensilla is scarce when compared to other arachnid orders, especially concerning internal morphology. Using scanning (SEM) and transmission (TEM) electron microscopy, we investigated tarsal sensilla on the distal tarsomeres (DT) of all leg pairs in Heteromitobates discolor (Laniatores, Gonyleptidae). Furthermore, we explored the typological diversity of sensilla present on the DT I and II in members of the suborder Laniatores, which include two thirds of the formally described opilionid fauna, using species from 17 families representing all main laniatorian lineages. Our data revealed that DT I and II of H. discolor are equipped with wall-pored falciform hairs (two types), wall-pored sensilla chaetica (two types) and tip-pored sensilla chaetica, while DT III and IV are mainly covered with trichomes (non-sensory) and tip-pored sensilla chaetica. The ultrastructural characteristics support an olfactory function for all wall-pored sensilla and a dual gustatory/mechanoreceptive function for tip-pored sensilla chaetica. Based on our comparative SEM survey, we show that wall-pored sensilla occur in all investigated Laniatores, demonstrating their widespread occurrence in the suborder and highlighting the importance of both legs I and II as the sensory appendages of laniatorean harvestmen. Our results provide the first morphological evidence for olfactory receptors in Laniatores and suggest that olfaction is more important for harvestmen than previously thought.     

The price of safety: food deprivation in early life influences the efficacy of chemical defence in an aposematic moth

Aposematism is the combination of a primary signal with a secondary defence that predators must learn to associate with one another. However, variation in the level of defence, both within and between species, is very common. As secondary defences influence individual fitness, this variation in quality and quantity requires an evolutionary explanation, particularly as it may or may not correlate with variation in primary signals. The costs of defence production are expected to play a considerable role in generating this variation, yet studies of the cost of chemical defence have focused on species that sequester their defences, while studies in species that produce them de novo are scarce. Here we examine effects of resource availability on the production of chemical defences in female wood tiger moths Arctia plantaginis. This species produces defensive fluids when attacked, and advertises this protection with bright colours on its hindwings. Furthermore, the chemicals in these fluids are produced de novo. In order to establish if the production of this chemical protection is costly, and thus resource‐limited, we manipulated resource availability (i.e. food) during larval development and measured its subsequent effects on adult chemical defence. We presented defensive fluids from female moths to wild blue tits, in the absence of any visual cues, to determine their effectiveness against avian predators. Our results demonstrate that the defensive fluids produced by female moths repel birds, and that these defences require resource investment to produce. We found that moths that were resource‐limited during development had less effective chemical defences, despite producing the same volume of defensive fluids as the control moths. As a reduction in available resources negatively influences the effectiveness of the chemical defence, resource availability may explain the variation seen among individuals.     

Ultrastructure of the sexually dimorphic tarsal glands and tegumental glands in gonyleptoid harvestmen (Opiliones,Laniatores)

In at least four closely related families of the diverse harvestmen lineage Gonyleptoidea, males may possess sexually dimorphic tarsal glands in the swollen tarsomeres of the basitarsus and/or metatarsus of leg I. The first histological and ultrastructural examination of the sexually dimorphic tarsal glands in leg I focused only on Manaosbiidae. In this study, we examine the morphology and ultrastructure of the sexually dimorphic glands, and their associated glandular openings, found in the basitarsus and/or metatarsus of leg I of males representing Cosmetidae, Gonyleptidae, and Cranaidae (glandular openings only). In cosmetids and gonyleptids, the tarsal glands are made up of 20–60 glandular units that form distinct groups within the prolateral and retrolateral half of the tarsomere. Each glandular unit consists of a pair of terminal secretory cells, an intercalary cell wrapped around the receiving canal, and a canal cell tightly wrapped around the length of the conducting canal. Cosmetidae, Gonyleptidae, and Cranaidae exhibit remarkably similar tarsal glands and gland openings although the location of the glands in the leg differs slightly among them. Males of these three families exhibit markedly different glands and glandular openings compared to males of the family Manaosbiidae. The sexually dimorphic tarsal glands may provide an important morphological character for determining phylogenetic relationships among gonyleptoid families. Finally, we provide morphological and ultrastructural data for the common tegumental glands. These data indicate that the sexually dimorphic tarsal glands are strikingly similar to, and may possibly be derived from, the tegumental glands. J. Morphol. 274:1203–1215, 2013. © 2013 Wiley Periodicals, Inc.     

Phylogeny of harvestmen family Gonyleptidae inferred from a multilocus approach (Arachnida: Opiliones)

Gonyleptidae is the second most diverse harvestmen family and the most studied in terms of morphology, behaviour, and ecology. Despite this, few phylogenetic studies have focused on gonyleptids, and those are based on a very limited number of taxa. We addressed this gap by constructing a phylogenetic hypothesis of the family using 101 taxa from all 16 gonyleptid subfamilies and four mitochondrial and nuclear loci (COI, 28S rRNA, 12S rRNA, and 16S rRNA). These were analysed under parsimony and likelihood optimality criteria (and using direct optimization for the former). Relationships among Gonyleptoidea and within each subfamily of Gonyleptidae were largely congruent between parsimony and maximum‐likelihood approaches. Taxonomic actions from our phylogeny include the following: Tricommatidae, new status, is restored as a family; Metasarcidae, new status, is recognized as a family and considered sister to the Cosmetidae; and Cranainae and Manaosbiinae are suggested as members of Gonyleptidae, restoring Roewer's concept of the family. Within Gonyleptidae, the “K92” group—composed of Sodreaninae, Caelopyginae, Hernandariinae, Progonyleptoidellinae, and Gonyleptinae—forms a clade, although the latter two subfamilies are not monophyletic. The genus Parampheres is here transferred to Caelopyginae, and “Multumbo” dimorphicus to Gonyleptinae. Gonyleptidae is characterized by the presence of a ventral process on the penis glans and a bifid apophysis on the male coxa IV. The long‐legged Mitobatinae can be considered monophyletic only if some short‐legged pachylines are included, or if we assume that elongate legs arose twice independently (in the true mitobatine genera and in Longiperna). Pachylinae, the most diverse gonyleptid subfamily, represents several distinct lineages. We further conclude that the traditional use of a small set of morphological characters in the systematics of Gonyleptidae is unable to explain the complex evolution of the family.     

Interspecific,ontogenetic, and sexual variation in ozopore morphology among cosmetid harvestmen (Arachnida,Opiliones, Laniatores)

The ozopores of cosmetid harvestmen rest upon lateral projections of the carapace, have simple or highly reduced channels, and are partially obscured by enlarged dorsal processes associated with coxae I and II. Rather than use scent gland secretions to form a chemical shield on the dorsum, the cosmetid harvestman exhibits a unique defensive behavior known as “leg dabbing” in which the distal tip of tarsus I or II is dipped into fluid that accumulate at the base of coxa II and the droplet on the tarsus is pointed toward the predator. Relatively little is known about interspecific variation in ozopore morphology among cosmetid harvestmen. In this study, we used scanning electron microscopy to examine the ozopores of males and females of nine species as well as those of antepenultimate nymphs for two species. Among adults, we found differences between species in the shapes of the ozopores (round or subtriangular), the morphology of the dorsal and lateral channels (if present), and the relative size, shape and armature of the dorsal posterior process (dpp) of coxa I and the dorsal anterior process (dap) of coxa II. Our observations suggest that the morphology of dpp I and dap II could be sources for systematic characters in future phylogenetic studies of the Cosmetidae. We observed ontogenetic differences but relatively little intersexual variation in the morphology of the ozopore. The ozopores of nymphs are generally more oval than those of adults and the opening of the ozopore of the nymph is less obstructed, if at all, by the dorsal coxal processes of legs I–II. These morphological differences suggest that nymphs may use scent gland secretions in a manner different from that of adults.     

To be or not to be convergent in salicin-based defence in chrysomeline leaf beetle larvae: evidence from Phratora vitellinae salicyl alcohol oxidase

Glandular chemical defence relying on the action of salicylaldehyde is characteristic for Chrysomela leaf beetle larvae. The salicylaldehyde precursor salicin, sequestered from salicaceous host plants, is deglucosylated and the aglycon further oxidized by a salicyl alcohol oxidase (SAO) to the respective aldehyde. SAOs, key enzymes in salicin-based glandular chemical defence, were previously identified and shown to be of a single evolutionary origin in Chrysomela species. We here identified and characterized SAO of Phratora vitellinae, the only species outside the genus Chrysomela that produce salicylaldehyde as a defensive compound. Although Chrysomela and Phratora are not closest relatives, their SAOs share glucose-methanol-choline oxidoreductase (GMC) affiliation, a specific GMCi subfamily ancestor, glandular tissue-specific expression and almost identical gene architectures. Together, this strongly supports a single origin of SAOs of both Chrysomela and Phratora. Closely related species of Chrysomela and P. vitellinae use iridoids as defensive compounds, which are like salicylaldehyde synthesized by the consecutive action of glucosidase and oxidase. However, we elucidated SAO-like sequences but no SAO proteins in the glandular secretion of iridoid producers. These findings support a different evolutionary history of SAO, related genes and other oxidases involved in chemical defence in the glandular system of salicylaldehyde and iridoid-producing leaf beetle larvae.     

Does ant predation favour leaf beetle specialization on toxic host plants?

Generalist predators are frequently seen as evolutionary forces that narrow the host range in herbivorous insects. Predators may favour specialization of herbivores on host plants containing toxic chemicals (which can be used by herbivores for their own defence) if host plant‐derived defences provide better protection from enemies than do autogenously produced defences. We compared the effectiveness of these two defensive strategies in the larvae of six species of leaf beetle (Chrysomelidae) against wood ants (Formica rufa group) in field experiments. Ants were more strongly repelled by larvae with host plant‐derived, salicylaldehyde‐containing secretions than by larvae with various autogenous secretions, but collectively foraging ants ultimately overcame any type of chemical defence by social interactions, chemical signalling, and olfactory learning. As a result, ants killed all larvae of Chrysomela lapponica defended by salicylaldehyde‐containing secretions within 2 days of their introduction to willows within 15 m of ant nests. We conclude that in the field neither type of chemical defence provides complete protection against wood ants in the vicinity of their nests, and that evolutionary shifts from autogenous production of secretion to sequestration of plant allelochemicals in leaf beetles may be favoured mostly at low ant densities on the periphery of ant foraging areas.     

Conventional and ultrastructural analyses of the chromosomes of Discocyrtus pectinifemur (Opiliones, Laniatores, Gonyleptidae)

Among the Opiliones, species of the suborders Cyphophthalmi, Eupnoi, Dyspnoi and Laniatores have shown very diverse diploid chromosome numbers. However, only certain Eupnoi species exhibit XY/XX and ZZ/ZW sex chromosome systems. Considering the scarcity of karyotypical information and the absence of structurally identifiable sex chromosomes in the suborder Laniatores, we decided to analyse the chromosomes and bivalents of Discocyrtus pectinifemur (Gonyleptidae) to identify possible sex differences. Testicular cells examined under light microscopy showed a high diploid number, 2 n  = 88, meta/submetacentric chromosome morphology and a nucleolar organizer region on pair 35. Prophase I microspreading observed in transmission electron microscopy exhibited 44 synaptonemal complexes with similar electron density and thickness. The total and regular synapsis between the chromosomes of the bivalents was also noted in pachytene nuclei. Male mitotic and meiotic chromosomes revealed no distinct characteristic that could be related to the occurrence of heteromorphic sex chromosomes. Evolutionary trends of chromosome differentiation in the four suborders of Opiliones are discussed here.     

Context-dependent defence in terrestrial plants: the effects of light and nutrient availability on plant resistance against herbivory

The context‐dependent defence (CDD) hypothesis predicts that defence levels of plant species against herbivory are not fixed but vary with environmental conditions, in a way that is specific for plant species that share evolutionary adaptations to resource conditions exemplified by similar maximum relative growth rates. More specifically, we expected plants from resource‐poor environments to display high defence levels but not when grown under resource‐rich conditions, whereas the reverse – plants from resource‐rich conditions displaying low defence levels but not when grown under resource‐poor conditions – is not necessarily the case. In this study, we used multiple‐choice bioassays in which leaf discs were fed to larvae of Spodoptera exigua (Hübner) (Lepidoptera: Noctuidae) as an efficient and effective way of indicating plant defence levels. This generalist herbivore was capable of detecting both inter‐ and intraspecific differences in defence among plant species. The CDD was tested by exploring the effects of various experimental resource conditions (light, nutrients) upon the herbivore preferences and by comparing these preferences with the maximum relative growth rate of plant species. The experimental results provide general support for the CDD hypothesis with respect to nutrient‐level variation but the effects were not related to the origin of the plant species tested. Variation in light conditions did not result in consistent effects upon herbivore preferences. The CDD therefore can be formulated more precisely as: defence levels of plant species vary under different environmental conditions but in a way that is specific for plant species that share evolutionary adaptations to similar nutrient conditions. This more precise CDD hypothesis is a useful addition to existing optimal‐defence theory because of its focus on the possible plastic effects of resource conditions upon plant defence levels. This is relevant when designing experimental plant–herbivore studies.     

Species with a chemical defence,but not chemical offence,live longer

Evolutionary hypotheses for ageing generally predict that delayed senescence should evolve in organisms that experience lower extrinsic mortality. Thus, one might expect species that are highly toxic or venomous (i.e. chemically protected) will have longer lifespans than related species that are not likewise protected. This remarkable relationship has been suggested to occur in amphibians and snakes. First, we show that chemical protection is highly conserved in several lineages of amphibians and snakes. Therefore, accounting for phylogenetic autocorrelation is critical when conservatively testing evolutionary hypotheses because species may possess similar longevities and defensive attributes simply through shared ancestry. Herein, we compare maximum longevity of chemically protected and nonprotected species, controlling for potential nonindependence of traits among species using recently available phylogenies. Our analyses confirm that longevity is positively correlated with body size in both groups which is consistent with life‐history theory. We also show that maximum lifespan was positively associated with chemical protection in amphibian species but not in snakes. Chemical protection is defensive in amphibians, but primarily offensive (involved in prey capture) in snakes. Thus, we find that although chemical defence in amphibians favours long life, there is no evidence that chemical offence in snakes does the same.     

Pollen feeding,resource allocation and the evolution of chemical defence in passion vine butterflies

Evolution of pollen feeding in Heliconius has allowed exploitation of rich amino acid sources and dramatically reorganized life‐history traits. In Heliconius, eggs are produced mainly from adult‐acquired resources, leaving somatic development and maintenance to larva effort. This innovation may also have spurred evolution of chemical defence via amino acid‐derived cyanogenic glycosides. In contrast, nonpollen‐feeding heliconiines must rely almost exclusively on larval‐acquired resources for both reproduction and defence. We tested whether adult amino acid intake has an immediate influence on cyanogenesis in Heliconius. Because Heliconius are more distasteful to bird predators than close relatives that do not utilize pollen, we also compared cyanogenesis due to larval input across Heliconius species and nonpollen‐feeding relatives. Except for one species, we found that varying the amino acid diet of an adult Heliconius has negligible effect on its cyanide concentration. Adults denied amino acids showed no decrease in cyanide and no adults showed cyanide increase when fed amino acids. Yet, pollen‐feeding butterflies were capable of producing more defence than nonpollen‐feeding relatives and differences were detectable in freshly emerged adults, before input of adult resources. Our data points to a larger role of larval input in adult chemical defence. This coupled with the compartmentalization of adult nutrition to reproduction and longevity suggests that one evolutionary consequence of pollen feeding, shifting the burden of reproduction to adults, is to allow the evolution of greater allocation of host plant amino acids to defensive compounds by larvae.     

The development of butterfly settling posture: the role of predators, climate, hostplant-habitat and phylogeny

A model is described that explains the evolution of adult butterfly settling posture. The role of climate and the activity of butterflies is fundamental in determining the effectiveness of primary and secondary visual defence systems based on wing colour and pattern. Both dorsal (open winged) and lateral (closed wing) postures can be regarded as evolutionarily conservative; common postures are found within almost all sub-families. Lateral postures tend to be associated with cool temperate and arctic climates. Conditions that are marginal for activity place an emphasis on the development of underside primary defence, uncompromised by secondary visual defences. In turn, any primary defensive function of the upper surface is reduced but secondary defence may be emphasized. There is interaction between segregation of functions on different wing surfaces and the development of lateral posture. The use of predictable hostplant-habitat structures reduces the role of visual communication in mate-location and facilitates the adoption of a lateral resting posture and a cryptic underside wing pattern. When hostplant-habitat structures are unpredictable but a lateral posture is adopted, primary defence is more important than visual communication for the resting insect. Adjustments of wing morphology facilitate postural conservatism, allowing species to retain particular postures in new hostplant-habitats and climatic zones.