Nuptial Gifts Research Articles

The role of functional constraints in nonrandom mating patterns for a dance fly with female ornaments.

Most hypotheses to explain nonrandom mating patterns invoke mate choice, particularly in species that display elaborate ornaments. However, conflicting selection pressures on traits can result in functional constraints that can also cause nonrandom mating patterns. We tested for functional load-lifting constraints during aerial copulation in Rhamphomyia longicauda, a species of dance fly that displays multiple extravagant female-specific ornaments that are unusual among sexual traits because they are under stabilizing selection. R.longicauda males provide females with a nuptial gift before engaging in aerial mating, and the male bears the entire weight of the female and nuptial gift for the duration of copulation. In theory, a male's ability to carry females and nuptial gifts could constrain pairing opportunities for the heaviest females, as reported for nonornamented dance flies. In concert with directional preferences for large females with mature eggs, such a load-lifting constraint could produce the stabilizing selection on female size previously observed in this species. We therefore tested whether wild-caught male R.longicauda collected during copulation were experiencing load-lift limitations by comparing the mass carried by males during copulation with the male's wing loading traits. We also performed permutation tests to determine whether the loads carried by males during copulation were lighter than expected. We found that heavier males are more often found mating with heavier females suggesting that whereas R.longicauda males do not experience a load-lift constraint, there is a strong relationship of assortative mating by mass. We suggest that active male mate choice for intermediately adorned females is more likely to be causing the nonrandom mating patterns observed in R.longicauda.

The effect of nuptial gift number on fertilization success in a Hawaiian swordtail cricket

In many insects, males transfer nuptial gifts to females prior to, during, or after copulation. Nuptial gifts comprise any form of non-gametic material transfer, such as glandular secretions, prey items, and spermatophores. These gifts can increase male fitness by facilitating copulation or sperm transfer or by promoting the female’s use of the focal male’s sperm. However, when a female mates with multiple males, the relationships between the relative size, number, or quality of nuptial gifts that each male donates and the proportion of offspring that each male sires are unknown in many cases. Here, we assessed these relationships in the Hawaiian swordtail cricket Laupala cerasina. We experimentally manipulated the number of gifts a female received from two male mating partners in sequence, with the first male giving either more, fewer, or an equal number of gifts relative to the second male. We found that there was a significant positive relationship between nuptial gift number and paternity share. In addition, we found considerable first-male sperm precedence, regardless of gift contribution. Finally, offspring from second males tended to be produced later and to be part of larger families. These results show that both nuptial gift number and mating order play important roles in sperm use patterns and fertilization success in this species. SIGNIFICANCE STATEMENT: In many insects, males transfer nuptial gifts (a token, often nutritional, gift) to females prior to, during, or after copulation. In the Hawaiian swordtail cricket Laupala cerasina, males transfer a series of nuptial gifts in the form of spermless spermatophores, to females during courtship. Moreover, males experience sperm competition as females of this species are known to mate multiply. By manipulating the number of gifts transferred, we tested the hypothesis that males who transfer more nuptial gifts achieve higher fitness by fathering more offspring. We found a significant positive relationship between gift number and the proportion of offspring a male sires. In addition, controlling for gift number, the first male to mate with a female achieves more paternity. These results show that both nuptial gift number and mating order affect sperm use patterns and fertilization success in this species.

Male Bush-Crickets in Female-Biased Environment Allocate Fewer Sperm Per Ejaculation

The operational sex ratio (OSR) is one of the most important ecological factors affecting the structure of mating systems and individual mating investment. Bush cricket males produce a highly costly nuptial gift during mating, so it is expected that OSR would affect this investment. In this study, we confronted the bush cricket Isophya rizeensis with three different OSR environments, measuring effects on the males' spermatophore, spermatophylax, ampulla weight, and absolute sperm transfer. As expected, male I. rizeensis showed a decrease in the transferred sperm in a female-biased environment. When mating in different OSR environments, males did not modify their behavioral strategies with respect to spermatophore transfer and copulation duration, which was largely influenced by male body size, likely due to the high costs of nuptial gifts. Although we dismiss the “longer copulation durations function as a mate assessment period” hypothesis, longer copulations positively affect spermatophore size and sperm number.

Maintenance of deceptive gifts in a natural spider population: ecological and demographic factors

AbstractAlternative mating tactics are expected to occur predominantly when mate competition is intense, resources are in short supply, or as a result of asymmetric power relationships between individuals. Males of the nuptial gift-giving spider Pisaura mirabilis use a prevailing tactic of offering a nutritive gift (insect prey) and a deceptive tactic of offering a worthless gift (consumed prey) to prospective mates. If the male’s tactic depends on precopulatory male–male competition, worthless gifts should occur primarily late in the season, when the operational sex ratio (OSR) becomes male-biased. If it depends on resource availability and/or postcopulatory sexual selection (sperm competition), worthless gifts should occur mostly early in the mating season, when prey availability is low and most females are unmated (i.e., postcopulatory sexual selection is weak). Nuptial gift construction correlated positively with prey availability and negatively with OSR, suggesting that males increase reproductive effort when resource and mate availability increase. We did not find evidence for body condition affecting male tactic use. Male size had a marked effect on the reproductive tactic employed. Males that matured early in the season were very small and employed mostly the nutritive gift tactic during their short life. Among the males that matured later and persisted through the season, relatively small males employed the worthless gift tactic whereas large males employed the nutritive gift tactic. We suggest that the existence of 2 distinct life-history strategies among males (early small and late large size) interacts with environmental and demographic conditions to maintain the deceptive tactic.

New cockroaches (Insecta, Blattaria, Fuziidae) from the Middle Jurassic Jiulongshan Formation in northeastern China

LIANG, J., SHIH, C., WANG, L., & REN, D., 26 March 2019. New cockroaches (Insecta, Blattaria, Fuziidae) from the Middle Jurassic Jiulongshan Formation in northeastern China. Alcheringa 43, 441–448. ISSN 0311-5518.Fuziidae is a significant cockroach family reported only from the Middle Jurassic Jiulongshan Formation of northeastern China. Male Fuziidae with forceps-like cerci are unique in the 320 Ma history of cockroaches. Longifuzia pectinata gen. et sp. nov. is described from the Jiulongshan Formation based on four male specimens. It can be distinguished from other fuziids by its larger body size, extremely long telescopic abdomen, numerous forewing veins, characteristic coloration on the forewing and unique male genitalia. Three of four type specimens have asymmetric venation in the wings. The narrow and elongate body shape is suggestive of alternative, non-standard diets because a wide (fat) body is necessary for nitrogen fixation in cockroaches. Nevertheless, well-developed male tergal glands provide evidence of nuptial female feeding on nitrogen provisions. This new taxon expands the known diversity and highlights the morphological disparity of this family at the Daohugou locality in northeastern China.Junhui Liang* [liangjh0602@126.com], Tianjin Natural History Museum, 31 Youyi Road, Hexi District, Tianjin, 300201, PR China; Chungkun Shih† [chungkun.shih@gmail.com], College of Life Sciences, Capital Normal University, 105 Xisanhuanbeilu, Haidian District, Beijing, 100048, PR China; Lixia Wang [wlxwlx@163.com], The Geological Museum of China, Xisi, Xicheng District, Beijing 100034, PR China; Dong Ren [rendong@mail.cnu.edu.cn], College of Life Sciences, Capital Normal University, 105 Xisanhuanbeilu, Haidian District, Beijing, 100048, PR China. *Also affiliated with: College of Life Sciences, Capital Normal University, 105 Xisanhuanbeilu, Haidian District, Beijing, 100048, PR China. †Also affiliated with: Department of Paleobiology, National Museum of Natural History, Smithsonian Institution, Washington, DC 20013, USA.

Taxonomic revision of the dwarf spider genus Shaanxinus Tanasevitch, 2006 (Araneae, Linyphiidae, Erigoninae), with new species from Taiwan and Vietnam

Dwarf spiders are of special interest due to their sexually dimorphic prosomal structures in males. Glandular secretions within these structures serve as nuptial gifts, and thus sexual selection may have contributed to their high species richness. However, species diversity of dwarf spiders in East Asia is yet understudied. Here, we review the erigonine genus Shaanxinus Tanasevitch, 2006, and describe 13 new species from Taiwan: S. magniclypeus sp. n. (♂♀), S. shihchoensis sp. n. (♂♀), S. shoukaensis sp. n. (♂♀), S. hirticephalus sp. n. (♂♀), S. mingchihensis sp. n. (♂♀), S. makauyensis sp. n. (♂♀), S. lixiangae sp. n. (♂♀), S. curviductus sp. n. (♂♀), S. tsou sp. n. (♂♀), S. hehuanensis sp. n. (♂♀), S. seediq sp. n. (♂♀), S. meifengensis sp. n. (♂♀), and S. atayal sp. n. (♂♀). In addition, one new species from Vietnam, S. tamdaoensis sp. n. (♂), is described from museum material. We reconstructed the dimension of glandular tissues associated with male prosoma modifications in Shaanxinus, as well as the detailed palpal structure by micro-computer tomography. Placement within Shaanxinus and intrageneric relationships were inferred by means of a cladistic analysis based on morphological characters. Sequences of COI, 16S, and 28S genetic markers corroborated the monophyly of some species, as well as male-female matching. Poly-/paraphyly of morphologically delimitated species in the mitochondrial DNA (mtDNA) trees led to the discovery of two seemingly identical species, for which diagnostic morphological features could then be further identified. We discuss incomplete lineage sorting and introgression as possible causes of mtDNA poly-/paraphyly in morphologically indistinguishable specimens.

Attraction of the Green Lacewing Chrysoperla comanche (Neuroptera: Chrysopidae) to Yeast

Many adult Chrysoperla comanche (Stephens) green lacewings were caught in traps baited with live yeast cultures during tests designed to catch olive fruit flies. All 13 yeast species tested were more attractive than the industry-standard dried torula yeast (Cyberlindnera jadinii; syn. Candida utilis). Live C. jadinii culture attracted significantly more lacewings than the inactive dried-pellet form of the same yeast species, demonstrating that volatiles from live yeast cultures attract adults of this lacewing. Odor profiles for two of the highly active yeasts tested herein (Lachancea thermotolerans and Solicoccozyma terrea) were similar to that for Metschnikowia pulcherrima, a yeast species isolated earlier from the gut diverticulum of Chrysoperla rufilabris. A new Metschnikowia species (M. chrysoperlae), along with two new Candida spp. that were recently realigned to one of the Metschnikowia clades (M. picachoensis and M. pimensis), were also identified from the diverticulum of C. comanche. Thus, one clade of Metschnikowia yeasts that commonly occur in floral nectar appears to exhibit mutualistic symbioses with Chrysoperla green lacewings. Both male and female C. comanche adults were attracted in the present study, and we speculate that males have exploited this symbiosis by offering Metschnikowia-laden regurgitant, including attractive volatiles, to females ('mating trophallaxis') as a nuptial gift.

Comparative evidence supports a role for reproductive allocation in the evolution of female ornament diversity

1. Sexually selected ornaments are highly variable, even among closely related species, and the ultimate causes of variation in ornament evolution are unclear, including in rare cases of female ornament expression. One hypothesis is that differences across species in female reproductive allocation may help to explain patterns of female ornament expression among insects with nuptial gifts.2. Dance flies (Diptera: Empididae: Empidinae) vary considerably among species in the presence and extravagance of female ornaments, which probably evolved through female contests for mates. In most dance flies, adult females appear to acquire all their dietary protein from nuptial gifts provided by males during mating. The importance of nuptial feeding on egg development is not yet known.3. To test the prediction that the presence of female ornaments reflects differences in the degree to which females rely on nuptial feeding for egg development, egg development was examined in wild females of two species, one ornamented and the other unornamented. An ageing technique based on cuticular bands was validated, which permitted a regression of egg size on adult age.4. We found that egg development depended on mating status in the ornamented species alone, meaning the eggs of unmated females of the ornamented species did not develop. This contrast across species is consistent with expectations that females of different species vary in their dependence on nuptial gifts for egg development.5. These findings provide preliminary support for the hypothesis that differences in reproductive allocation mediate the intensity of female contests for nuptial gifts.

Fitness effects of nuptial gifts in the spiderPisaura mirabilis: examination under an alternative feeding regime

Nuptial feeding has variable effects on fitness within a species, partly driven by variation in female diet. We investigate nuptial feeding in the spider Pisaura mirabilis (Clerck, 1757) under a feeding regime that has not been explored: starvation after mating and gift consumption. We vary gift size and gift number to examine the effects on mating behavior and components of female fitness. With regard to gift size, copulation duration increased with larger gift size, but no component of female fitness was affected (time to oviposition, egg sac mass, female lifespan). These results corroborate other examinations of gift size in P. mirabilis. Given a likely male benefit (prolonged copulation) for larger gift size and no demonstrated female benefit, sexual conflict stands as a likely explanation for male benefits due to large nuptial gift size. With regard to gift number, components of female fitness were not affected by the consumption of one or two extra gifts. This agrees with other studies, although we note that some experiments have found the consumption of extra gifts to increase female fitness. As for males, they were more likely to copulate when they had gifts, as in other studies. We conclude some support for sexual congruence with regard to gift number, as males and females stand to benefit simultaneously from the mere presence of the gift, and females might benefit from the consumption of multiple gifts. Thus, both sexual conflict and sexual congruence appear to be at work regarding the evolution of nuptial gifts in Pisaura mirabilis.

Copulatory mechanism and functional morphology of genitalia and anal horn of the scorpionfly Cerapanorpa dubia (Mecoptera: Panorpidae).

The scorpionfly genus Cerapanorpa is characterized by the male possessing a single finger-like anal horn on the posterior portion of tergite VI. However, the functional morphology of this anal horn and the genitalia have not been studied to date. Herein, we investigated the functional morphology of the genitalia and the nongenital structures of the scorpionfly Cerapanorpa dubia by observing the mating process and dissecting the freeze-fixated pairs in copula to reveal the copulatory mechanism. The male C. dubia provides a solid salivary mass to the female as a nuptial gift prior to copulation. When the female starts to feed on the gift, the male uses his notal organ and complex genital structures to control the closest wing and genitalia of the female to establish a V-shaped mating position. In the maintenance phase of copulation, the male uses his anal horn in cooperation with the basally-constricted abdominal segment VII to clamp female abdominal segment VIII. The male hypovalves grasp female cerci, and move up and down rhythmically. The paired parameres clasp both sides of female tergite IX. The basal processes on male gonostyli grip the pleural membranes of the female genital chamber. In the sperm transfer phase, the male aedeagus directly couples with the female medigynium to transmit sperm by connecting his phallotreme to the female's copulatory pore. The evolution of the male complex grasping structures in Panorpidae is also briefly discussed.

Investigating the role of a mud structure in a fiddler crab: do semidomes have a reproductive function?

Sensory traps occur when a signal evolves to mimic a cue to which the receiver responds favorably in another context. For example, if females are attracted to the noise a prey item makes, then a conspecific male can mimic that noise, thereby attracting females in the context of mating. Thus, sensory traps can be beneficial to receivers since attraction helps locating males more efficiently. But what happens when receivers are less attracted by the sensory trap outside of the original context (due to the cost of the response for instance)? Does this weaken and eventually “break” the sensory trap? Here, we show that a rare, small mud structure (a semidome) built by some male fiddler crabs (Austruca mjoebergi) at their burrow entrances are most likely relics of the sensory traps used by other fiddler crabs (the larger, far more abundant hoods of Leptuca species). Females of A. mjoebergi have retained their tendency to move towards vertical structures for protection when threatened by a predator—the original context thought to be important in the evolution of sensory traps in other fiddler crab species. However, females show no significant preference for males with semidomes. Additionally, males do not use the semidomes as landmarks to relocate their burrows when courting. The results suggest that in A. mjoebergi, semidomes do not function as sensory traps, despite the existence of a pre-existing bias in females. We suggest that semidomes have lost their attractiveness in the mating context due to ecological features, such as predation and environmental heterogeneity. There is growing evidence of sensory traps in many animal species, with an ever-widening range of contexts from nuptial gift giving in spiders to egg recognition in non-brood-parasitized birds. While we are starting to understand the significance of sensory traps, little thought has been given to what happens when they break down. If there is a change in the original context that favored the receiver’s response, then there is likely to be a subsequent change in the receiver’s bias and finally, in the sensory trap. If the mimic of the original stimulus does not induce a beneficial response in the receiver anymore, the sensory trap would become inefficient and stop being selected. The effect will be most profound when the sensory trap was costly to set up, since there will be selection against its retention. Here, we show that a sensory trap can become a relic when ecological conditions change and make it not functional anymore. To our knowledge, it is the first study providing such empirical evidence.

Quinolizidine and Pyrrolizidine Alkaloid Chemical Ecology - a Mini-Review on Their Similarities and Differences.

This mini-review summarizes over 40years of research on quinolizidine (QAs) and pyrrolizidine alkaloids (PAs). Emphasis is on the chemical ecology of both groups of alkaloids, which serve as general defense compounds against herbivores for the plants producing them. For QAs and PAs, a number of insects (aphids, moths, beetles) have acquired tolerance. These specialists store the alkaloids and use them as defense chemicals against predators. In some PA sequestering moths, the adaptation is even more intricate and advanced. PAs can function as a morphogen to induce the formation of male coremata, inflatable organs that dissipate pheromones. In these insects, PAs are additionally used as a precursor for male pheromones. Female moths utilize their own PAs and those obtained from males via the spermatophore as nuptial gift, to transfer them to the eggs that thus become chemically protected. Novel genomic technologies will allow deeper insights in the molecular evolution of these two classes of alkaloids in plant-insect interactions.

A review of the mechanisms and functional roles of male silk use in spider courtship and mating

Spiders are well known for using chemical, vibratory, tactile, and visual signals within mating contexts. All spiders produce silk, and even in non-web building spiders, silk is intimately tied to courtship and mating. Silk produced by females provides a transmission channel for male vibratory courtship signals, while webs and draglines provide a substrate for female sex pheromones. Observations of male spiders producing silk during sexual interactions are also common across phylogenetically widespread taxa. However, the function of male-produced silk in mating has received very little study. Exploring the function of male silk use during mating will provide a deeper understanding of the complex mating systems of spiders and allow tests of hypotheses about the evolution of male and female traits under sexual selection and/or conflict. In this review, we outline functional hypotheses that may explain each of the following three main categories of silk deposition males exhibit during courtship and mating: (1) silk deposition on females' webs or other silk structures, (2) silk deposition on females (‘bridal veils') and (3) silk associated with nuptial gifts. We then summarize the current knowledge of silk use by male spiders within these three categories and the types of mechanisms that may lead to functional effects, and discuss areas where future work can be targeted.

Nuptial gift chemistry reveals convergent evolution correlated with antagonism in mating systems of harvestmen (Arachnida, Opiliones).

Nuptial gifts are material donations given from male to female before or during copulation and are subject to sexual selection in a wide variety of taxa. The harvestman genus Leiobunum has emerged as a model system for understanding the evolution of reproductive morphology and behavior, as transitions between solicitous and antagonistic modes of courtship have occurred multiple times within the lineage and are correlated with convergence in genital morphology. We analyzed the free amino acid content of nuptial gift secretions from five species of Leiobunum using gas chromatography–mass spectrometry. Multivariate analysis of the free amino acid profiles revealed that, rather than clustering based on phylogenetic relationships, nuptial gift chemical composition was better predicted by genital morphology and behavior, suggesting that convergent evolution has acted on the chemical composition of the nuptial gift. In addition, we found that, species with solicitous courtship produce gifts consisting of a 19% larger proportion of essential amino acids as compared to those with more antagonistic courtship interactions. This work represents the first comparative study of nuptial gift chemistry within a phylogenetic framework in any animal group and as such contributes to our understanding of the evolution of reproductive diversity and the participant role of nuptial gift chemistry in mating system transitions.

Epigenetic paternal effects as costly, condition-dependent traits.

It is now recognized that post-copulatory traits, such as sperm and ejaculate production can impose metabolic costs, and such traits are therefore expected to exhibit condition-dependent expression, whereby, low condition individuals experience a greater marginal cost of investment compared to high condition individuals. Ejaculates are especially costly in species where males invest in offspring quality through nutrient-rich spermatophores or other seminal nuptial gifts. However, recent evidence shows that, in species where males do not provision females or offspring, males can still influence offspring development through paternal effects mediated by epigenetic factors, such as non-coding RNAs, DNA methylation and chromatin structure. Because such epigenetic paternal effects do not involve the transfer of substantial quantities of resources, such as nutrients, the costs of conferring such effects have not been considered. Here we argue that if selection favours paternal investment in offspring quality through epigenetic factors, then the epigenetic machinery required to bring about such effects may also be expected to evolve strongly condition-dependent expression. We outline indirect evidence suggesting that epigenetic paternal effects could impose substantial metabolic costs, consider the conditions under which selection may act on such effects, and suggest ways to test for differential costs and condition-dependence of these effects. Incorporating epigenetic paternal effects into condition-dependent life history theory will further our understanding of the heritability of fitness and the evolution of paternal investment strategies.

True deception during extra‐pair courtship feeding: cheating whiskered tern Chlidonias hybrida females perform better

Males of many bird species feed their mates during the pre‐incubation period. The food provisioned by males during these courtship feedings (CFs) represents the key source of energy for the female during egg formation. Non‐pair males may trade food for extra pair copulations (EPC) with females during extra pair courtship feeding (EPCF), while females may trade copulations for food with non‐pair males to obtain additional resources. Because EPCs can be costly to the females, they are expected to behave in ways that will deceive non‐pair males to obtain additional resources at no cost to themselves. We investigated EPCFs in whiskered terns Chlidonias hybrida breeding in food‐rich conditions, on carp ponds in southern Poland. Almost all CFs (n = 2751) took place during the female's fertile period and peaked just before clutch initiation. 10% of all CFs were performed by non‐pair males. Females tried to obtain food from the non‐pair male during 39% of EPCFs, by swindling (the female solicits a non‐social male for copulation and tries to swindle food with no cloacal contact) or by snatching (the female tries to take the gift without engaging in copulation). In the remaining 61% of EPCFs, females did not react or chased the visiting male away. The probability of a female's obtaining food during EPCF was much higher (0.69, 95% CI: 0.47–0.85) if she swindled rather than snatched (0.08, 95% CI: 0.02–0.22). Only 0.7% of EPCFs were followed by EPCs. The high availability of food in the study area allows males to perform frequent EPCFs, despite the very low probability of obtaining EPCs. This is the first time that ‘true deception’ during EPCFs has been reported in birds: swindling females obtain food from non‐pair males at no immediate detectable cost to themselves.

Male nutritional history affects female fecundity in a male-dimorphic mite: Evidence for a nuptial gift?

In male-dimorphic species, males are often either armoured ‘majors’ that can monopolise access to females, or unarmoured and defenceless ‘minors’ that cannot. However, majors, unlike minors, have to spend energy to maintain their weaponry. Like-for-like, this could mean that minors have relatively more energy available to increase their reproductive output through e.g. sperm competition, or the transference of nutrients by means of a nuptial gift. Such a fitness advantage to minors could therefore contribute to explaining the coexistence of both morphs in single populations. We tested if food-deprived females of the male-dimorphic bulb mite Rhizoglyphus robini produced more eggs when mated to a minor or to a major male, and whether egg production depended on whether their mates were starved or fed prior to mating. We found no effect of male morph on female fecundity, but females did produce more eggs when mated to previously fed males. We also found that females increased in mass, but males decreased in mass over the course of the experiment. From these observations we infer that fed males are able to transfer nutrients, a nuptial gift, to their mate. This is the first observation to suggest nuptial gift transfer in mites. Though males of both morphs appeared able to produce nuptial gifts; other factors, like habitat complexity, should be considered to identify fitness benefits of minor over major males to understand why the two morphs coexist.

Effect of mating on survival at low temperature in females of the Japanese common grass yellow, Eurema mandarina

1. In some insects that overwinter as adults, mating occurs both before and after overwintering. Two hypotheses have been proposed to explain the adaptive significance of pre‐overwintering copulation of females. One is the bet‐hedging hypothesis, which explains pre‐overwintering copulation as a preparation for less chance of mating in the following spring. The other is the nuptial gift hypothesis, which states that secretions derived from males increase overwintering success of females.2. In Eurema mandarina, both diapause autumn‐ and non‐diapause summer‐form male adults emerge with autumn‐form female adults in the last generation in a year. Most autumn‐form females mate with summer‐form males before winter, and re‐mate with autumn‐form males in the following spring. Because autumn‐form females have sufficient chances for mating after overwintering, the nuptial gift hypothesis has been regarded as the more probable hypothesis.3. To test the nuptial gift hypothesis, the survival period was compared under short‐day conditions at 10 °C between mated and unmated females that had been reared on sucrose solution at 25 °C for 15–21 days. The mated females had significantly greater longevity than the unmated females, supporting the nuptial gift hypothesis. Body size also affected the survival period.4. The results suggest that the nuptial gift is an important factor for the evolution of pre‐overwintering copulation in species in which females mate both before and after overwintering.

Cyanogenesis in Arthropods: From Chemical Warfare to Nuptial Gifts.

Chemical defences are key components in insect–plant interactions, as insects continuously learn to overcome plant defence systems by, e.g., detoxification, excretion or sequestration. Cyanogenic glucosides are natural products widespread in the plant kingdom, and also known to be present in arthropods. They are stabilised by a glucoside linkage, which is hydrolysed by the action of β-glucosidase enzymes, resulting in the release of toxic hydrogen cyanide and deterrent aldehydes or ketones. Such a binary system of components that are chemically inert when spatially separated provides an immediate defence against predators that cause tissue damage. Further roles in nitrogen metabolism and inter- and intraspecific communication has also been suggested for cyanogenic glucosides. In arthropods, cyanogenic glucosides are found in millipedes, centipedes, mites, beetles and bugs, and particularly within butterflies and moths. Cyanogenic glucosides may be even more widespread since many arthropod taxa have not yet been analysed for the presence of this class of natural products. In many instances, arthropods sequester cyanogenic glucosides or their precursors from food plants, thereby avoiding the demand for de novo biosynthesis and minimising the energy spent for defence. Nevertheless, several species of butterflies, moths and millipedes have been shown to biosynthesise cyanogenic glucosides de novo, and even more species have been hypothesised to do so. As for higher plant species, the specific steps in the pathway is catalysed by three enzymes, two cytochromes P450, a glycosyl transferase, and a general P450 oxidoreductase providing electrons to the P450s. The pathway for biosynthesis of cyanogenic glucosides in arthropods has most likely been assembled by recruitment of enzymes, which could most easily be adapted to acquire the required catalytic properties for manufacturing these compounds. The scattered phylogenetic distribution of cyanogenic glucosides in arthropods indicates that the ability to biosynthesise this class of natural products has evolved independently several times. This is corroborated by the characterised enzymes from the pathway in moths and millipedes. Since the biosynthetic pathway is hypothesised to have evolved convergently in plants as well, this would suggest that there is only one universal series of unique intermediates by which amino acids are efficiently converted into CNglcs in different Kingdoms of Life. For arthropods to handle ingestion of cyanogenic glucosides, an effective detoxification system is required. In butterflies and moths, hydrogen cyanide released from hydrolysis of cyanogenic glucosides is mainly detoxified by β-cyanoalanine synthase, while other arthropods use the enzyme rhodanese. The storage of cyanogenic glucosides and spatially separated hydrolytic enzymes (β-glucosidases and α-hydroxynitrile lyases) are important for an effective hydrogen cyanide release for defensive purposes. Accordingly, such hydrolytic enzymes are also present in many cyanogenic arthropods, and spatial separation has been shown in a few species. Although much knowledge regarding presence, biosynthesis, hydrolysis and detoxification of cyanogenic glucosides in arthropods has emerged in recent years, many exciting unanswered questions remain regarding the distribution, roles apart from defence, and convergent evolution of the metabolic pathways involved.

The Mating Behavior of Rhamphomyia pectinata (Empididae: Diptera) with Notes on Other Members of the Genus Found at the Same Locale in Northern Virginia

The previously unstudied empidid fly Rhamphomyia pectinata is, like many other members of the genus, a sex-role-reversed species with highly ornamented females that gather in swarms to await the arrival of prey-bearing males. Receptive males transfer their nuptial gifts to females before mating with them in the air. Rhamphomyia pectinata is diurnal, with swarming and copulations occurring in the afternoon. Other members of the genus occur at the study site but are crepuscular.