Misumenoides Formosipes Research Articles

Specificity of attraction to floral chemistry inMisumenoides formosipescrab spiders

Although our understanding of arachnid olfactory physiology remains relatively limited, studies continue to reveal the importance of chemical cues for many spider behaviors. Olfactory cues for detecting prey, navigating to foraging sites, or finding mates might be especially beneficial to cursorial and ambush spiders living in structurally complex habitats. Previous field results suggested that volatile plant chemical cues were important in Misumenoides formosipes Walckenaer 1837 (Thomisidae) navigation and led us to design olfactometer bioassays to test this hypothesis in the laboratory. In our olfactometer trials, crab spider males were attracted specifically to the floral scent of Rudbeckia hirta (a species on which M. formosipes is commonly found in the field), but not to volatiles from foliage of the same plant species nor to volatiles from foliage of Morus rubra. Male spiders also failed to display any attraction to the floral scent of Daucus carota, even though they commonly reside on that plant in the field. Female M. formosipes did not move toward R. hirta inflorescences as a first choice over a control, although they did spend more time in the olfactometer arm with the R. hirta treatment. Males' use of olfactory cues to locate R. hirta inflorescences should increase encounters with potential mates, given that females in our population are found on that substrate more predictably than on any other.

Impacts of temperature, hunger and reproductive condition on metabolic rates of flower-dwelling crab spiders (Araneae: Thomisidae)

Temperature strongly affects spider metabolic rate. Consequently, quantifying a species' temperature-metabolism relationship is useful in evaluating consequences of choices that affect body temperature. Body size also influences metabolic rate, and body size in spiders is strongly impacted by feeding and reproductive condition. Using adult female crab spiders, Misumenoides formosipes Walckenaer 1837 and Mecaphesa asperata (Hentz 1847) (formerly Misumenops asperatus) acclimated to field ambient conditions, I measured standard metabolic rates (SMR) over an ecologically relevant temperature range (10–40° C). I controlled hunger and reproductive condition of M. formosipes using starved (25 days post-feeding) or fed (7 days post-feeding) spiders, and virgin or mated spiders; in experiments with M. asperata, I used fed spiders of unknown reproductive status. Temperature strongly affected crab spider SMR, and both species showed similar temperature-SMR relationships. Mecaphesa asperata displayed equivalent temperature coefficients (Q10s – the factor by which a physiologic process changes with temperature) for SMR across the experimental temperature range, while M. formosipes had significantly higher Q10 at low temperature than at mid-range or high temperature; Q10s of the two species reflected previously determined impacts of temperature on hunting performance. Influence of hunger-reproductive condition on SMR of M. formosipes depended on how I accounted for body size; regardless of method, gravid spiders did not show elevated metabolic rate. Lastly, I combined crab spider SMR data with published SMR data to generate mass-metabolism equations for spiders; mass-scaling exponents approximated 0.67.

Navigation by Male Crab Spiders Misumenoides formosipes (Araneae: Thomisidae): Floral Cues May Aid in Locating Potential Mates

The crab spider Misumenoides formosipes is an ambush predator whose males search for relatively sedentary females within a heterogeneous habitat. Females are receptive to mating immediately after their adult molt and a male biased adult sex ratio together with precopulatory guarding places a premium on male ability to locate females quickly. It is unknown what cues males use to find females; we report here on male movements in association with floral cues. Males in field trials moved towards inflorescences more frequently when both visual and chemical cues were available, than when chemical cues were eliminated. Males in lab trials chose an inflorescence over leaf substrates even in the absence of visual cues. These findings support the hypothesis that M. formosipes males could utilize floral chemistry as a navigational cue in mate searches.

Is Contest Experience a Trump Card? The Interaction of Residency Status, Experience, and Body Size on Fighting Success in Misumenoides formosipes (Araneae: Thomisidae)

Game theory models predict that individuals in contests adjust their strategy appropriately to the current value of the contested resource and the resource holding potential (RHP) of their opponent. In the current investigation, I examined interactively operating, multiple contest asymmetries on dyadic disputes for precopulatory guarding positions in the crab spider Misumenoides formosipes. In contests between equally sized adult males with no previous contest experience, residents had clear advantages in fighting success over intruders. Asymmetries in experience predicted outcome when tested against residency status, and experience operating in concert with residency status predicted resolution when tested against size asymmetries. Data from this investigation suggest that crab spiders learn strategies through experience rather than rely solely on the assessment of their opponent's RHP before determining contest effort.

Tritrophic interactions in a pollination system: impacts of species composition and size of flower patches on the hunting success of a flower-dwelling spider.

Size and species composition of flower patches were manipulated to determine whether these factors exerted indirect effects on the hunting success of flower-dwelling spiders via direct effects on insect pollinators. Multivariate analysis of variance (MANOVA) of two pollinator response variables (visitation rate and visitor size) revealed a significant pollinator preference for Bidens aristosa (tickseed sunflower) over Solidago juncea (goldenrod) and for large patches of a given plant species over small patches. Bidens received significantly more pollinator visits per floral unit per unit time and attracted significantly larger insects than Solidago. The significant patch size effect seen in the MANOVA was driven by the strong impact of patch size on the size of insects visiting the experimental patches: the size (mass) of insects visiting large patches was significantly greater than the size of insects visiting small patches of a given plant species, but visitation rates to large and small patches of a given plant species were similar. MANOVA indicated that hunting success of a flower-dwelling crab spider, Misumenoides formosipes, was also significantly affected by species composition and size of flower patches. Three measures of spider hunting success (rate of mass gain and its components, total prey mass captured per spider per day, and number of prey captured per spider per day) were evaluated, and the experimental treatments exerted similar effects on all three measures. Spiders occupying Bidens patches experienced greater hunting success than spiders occupying Solidago patches, and in patches of a given plant species, spiders occupying large patches experienced greater hunting success than spiders occupying small patches. The pattern of spider hunting success most closely paralleled the pattern described by the size of insects visiting the patches (BL>BS=SL>SS), suggesting that the size of visiting pollinators, rather than frequency of visitation, exerted a greater influence on spider hunting success. Taxonomic composition of a spider's diet varied with the plant species occupied. The size of insects captured by spiders was significantly greater than average size of insects visiting the patches, indicating that spiders selectively captured larger pollinator taxa. Spider movements among patches revealed a pattern of migration from Solidago to Bidens.

Body Size, Leg Autotomy, and Prior Experience as Factors in the Fighting Success of Male Crab Spiders, Misumenoides formosipes

Game theory predicts which characteristics of male crab spiders should affect their success in mate-guarding contests. Previous data on Misumenoides formosipes suggested that body size and leg number influenced fight outcome, but the study had methodological problems. Using improved methods, we corroborated the size advantage but refuted the disadvantage of leg reduction. We also conducted the first test for an invertebrate on the effect that a single contest has on the outcome of subsequent contests. When size and residency status were controlled, prior winners defeated prior losers after only one contest experience. We discuss the importance of controlling for previous experiences in studies of contest resolution and the ramifications for both past and future studies.

DIET-INDUCED AND MORPHOLOGICAL COLOR CHANGES IN JUVENILE CRAB SPIDERS (ARANEAE, THOMISIDAE)

The effect of dietary pigments on abdominal color of juvenile spiders was examined in the laboratory using the flower-dwelling crab spiders Misumenops asperatus(Hentz 1847), Misumenoides formosipes (Walckenaer 1837), and Misumena vatia (Clerck 1757) (Thomisidae). Because these species lack hypodermal chromes, ingested prey pigments may show through the epidermis and affect opistho- somal coloration. Diet-induced color changes were restricted to the opisthosoma, and all three spider species responded similarly to dietary pigments. Opisthosomas of instars 2-4 fed red-eyed fruit flies turned pink, and the pink color faded back to the normal white over a period of 4-6 days. Opisthosomas of instars 5-7 fed red-eyed fruit flies remained white, as did opisthosomas of all instars fed white-eyed fruit flies (controls). In a field population of M. asperatus, 82% of spiders in July (instar 2), 93% of spiders in August (instars 3-4), and 8% of spiders in September (instar 5) had pink, orange, or brown opistho- somas. Yellow juveniles were also seen: 5% and 57% of M. asperatus observed in August and September, respectively, were yellow. Yellow juvenile M. formosipes were observed in the field as well. The yellow color did not result from dietary pigments, but was, rather, a morphological color change and included the prosoma and limbs, as well as the opisthosoma.

Mate Guarding and Aggression by the Crab Spider Misumena vatia in Relation to Female Reproductive Status and Sex Ratio

Current theory predicts that males should guard prereproductive females if they will thereby achieve sperm priority and that the propensity of males to guard prereproductive females, and aggression exhibited by both sexes at this time, should be related to their density and sex ratio. Low female density should select for males to guard prereproductive females, but a female-biased sex ratio should weaken any propensity for males to guard them. Low density and a female-biased sex ratio should favor a low level of aggression by both males and females. We tested these predictions with a low-density, female-biased population of the crab spider Misumena vatia. During experimental introductions only 10% (n = 40) of the males guarded penultimate-stage females through their final molt to copulate with them, even though penultimate females seldom responded aggressively to males in these trials (10%). Nearly all males mated soon after they found newly molted adult virgin females (94%: n = 31). Males guarded only 8% (n = 39) of the penultimate females censused in the field, but each male mated with the female it guarded as soon as that female molted. Only 22% (n = 23) of trials with two males and a penultimate female resulted in more than momentary physical contact between the males, and none resulted in injury. Thus, both predictions were based on the sex ratio, but only one of the two associated with population density, were confirmed. These results suggest that sex ratio is more important than density in dictating precopulatory guarding and aggression. The strongly female-biased sex ratio of Misumena may explain why males guard pre-reproductive females less frequently and exhibit less aggression than males in a population of the closely-related Misumenoides formosipes.

Crab spider hunting performance is temperature insensitive

Summary1. Laboratory and field experiments showed that the hunting performance of two flower‐dwelling crab spiders, Misumenops asperatus and Misumenoides formosipes, was thermally insensitive over a broad range of temperatures normally experienced by these spiders.2. In the laboratory, HP, a behavioural metric of spider hunting performance, was similar for spiders of a given species over an ≈ 30 °C temperature range.3. Spiders in the field captured predominantly hymenopterans and dipterans, and field hunting performance, measured as the number of prey captured per spider per day, also proved to be unaffected by temperature.4. These findings counter the general rule that physiological/ecological performance in terrestrial arthropods is temperature dependent.5. Freedom from temperature constraints on the capacity of crab spiders to capture prey may be due to the use of venom and/or to muscle physiological adaptations for anaerobic metabolism.6. Wide thermal performance breadth increases the spectrum of prey available to M. asperatus and M. formosipes by allowing spiders to hunt prey active during cooler periods of the day as well as those active during warmer periods.7. Wide thermal performance breadth also benefits M. asperatus and M. formosipes due to adult phenology; both species experience a seasonal temperature shift during the adult phase.

Why do male crab spiders drink nectar?

Misumenoides formosipes is a protandrous, semelparous crab spider common on flowers in North America. Females are 20–50 times heavier than males, which seldom feed on prey as adults, but search for and guard potential mates. Nectivory, previously unproven for spiders, was observed in male M. formosipes. Males were studied on Queen Anne's lace, Daucus carota, to determine the importance of nectar as an energy and water source and its effect on male longevity. Because of their low mass and large surface-to-volume ratio males were more prone to dehydration than females. Drinking nectar replaced fluid that males lost through evaporation, although dew and rainwater were more efficient sources of fluid because the volume per nectary was very small. Males preferred drinking a simulated nectar source (30% sucrose solution) to water, and even when satiated with water would still drink the sucrose solution, suggesting nectar was used as an energy source. Males offered nectar for an hour a day lived longer than males given only water. Nectar feeding may have evolved because of the selective advantage of increased longevity for male reproductive success.

Pre-copulatory guarding of penultimate females by male crab spiders, Misumenoides formosipes

Abstract. Previous studies have identified a first mate sperm priority pattern for spider species belonging to the Entelegynae, which are characterized in part by complex female genitalia. First mate sperm priority leads to the hypothesis that unmated females should be a particularly valuable resource from a male perspective and therefore pre-copulatory guarding of immature females is expected. Laboratory experiments with an entelegyne species, Misumenoides formosipes, supported the prediction that males would cohabit with penultimate females longer than with either adult-virgin or once-mated females, and field distributions of males corroborated these results. Males took up residence under inflorescences occupied by penultimate females and fought with introduced intruder males. In staged fights differences of 10% or greater in cephalothorax width of opponents influenced fight outcome, whereas body length and weight had no effect. Fights often resulted in leg autotomization and were sometimes lethal. The loss of a raptorial foreleg significantly reduced subsequent fighting success.

Factors affecting the reproductive success of the crab spider Misumenoides formosipes: the covariance between juvenile and adult traits

To examine the importance of covariance between stages in traits related to foraging, we quantified the relationships between reproductive success and sizerelated variability in weight gain in juvenile and adult instars of the crab spider Misumenoides formosipes (Araneae: Thomisidae). Prereproductive weight and fecundity are both highly correlated with carapace width, a linear measure of size which does not change within an instar. In field populations, adult females with larger carapaces gain more weight and are more likely to reproduce than females with smaller carapaces. The growth rate of spiders fed ad libitum in the laboratory is unrelated to size, suggesting that size-related differences in the field are due to variation in prey-capture success. Adult females with a carapace width less than 3.4 mm comprised 22% of the population, but were never found to reproduce. Of the individuals that did reproduce, a 17% increase in carapace width resulted in a 100% increase in fecundity. Juvenile stages must be examined to understand adult foraging and reproductive success, because the net weight gained by juvenile instars determines adult size. The final weight gained by spiders in the antepenultimate and penultimate instars explained nearly all the variation in carapace width in the penultimate and adult instars, respectively. We found that constraints on foraging in late juvenile stages are different from the adult stage. Penultimate foraging behavior differs from that of adults, because of constraints on foraging in the period preceding ecdysis. Additionally, in both late juvenile instars, carapace width had little or no effect on the final weight gained within the instar suggesting that factors that affect foraging are different between the juvenile and adult stages. These analyses stress the fact that to fully understand the effects of foraging on reproductive success, we must examine stage-specific constraints throughout an organism's life history.