Michael R. Maxwell’s research while affiliated with University of San Diego and other places

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.

Sexual cannibalism, the attack and consumption of the opposite sex by a conspecific during courtship, copulation, or soon after copulation, is widespread among invertebrates, but the causes of this behavior are not fully understood. We examine the mistaken identity hypothesis, which posits that non-copulatory cannibalism occurs because females do not recognize conspecific males as potential mates. This hypothesis predicts indiscriminate predatory behavior by females towards conspecific males and heterospecific prey. This prediction remains largely unexamined. We tested this prediction in the praying mantis Mantis religiosa (Mantodea: Mantidae) through two behavioral experiments. In experiment 1, we presented targets in isolation to females: dead conspecific males or dead common prey items from the field (grasshopper Chrysochraon dispar). In experiment 2, we presented simultaneous live targets to females: conspecific males and grasshoppers. In both experiments, we varied female mating status (virgin vs. mated). Results indicate some degree of attack discrimination by the females. In experiment 1, the females were significantly more likely to strike at the grasshoppers, and showed a shorter latency to strike at grasshoppers. In experiment 2, females tended to preferentially strike at the grasshoppers, although this result fell short of statistical significance. Female discrimination between the males and grasshoppers may be explained, in part, by the size difference between the males and grasshoppers. Female mating status did not affect the occurrence or latency to strike in either experiment. These results fail to strongly support the prediction of indiscriminate predatory behavior by females, while contributing to a broader taxonomic assessment of the mistaken identity hypothesis.

Development affects many components of life history and fitness, including body size. The present study examined the influence of developmental pattern, specifically the number of nymphal instars, on body size (pronotum length) in the praying mantid Stagmomantis limbata Hahn. Mantids were reared in the laboratory from hatching, on standardized diet, to examine variation in instar number. These lab data were then used to assess developmental patterns forfield-collected female nymphs. Laboratoryreared males and females varied in number of instars. Most females required 6 nymphal instars to reach adulthood (64%), whereas 36% underwent 7 instars. Seven-instar females reached the 4th, 5 th, and 6th instars faster than six-instar females, but had shorter pronota than the six-instar females at each of these stages. Seven-instar females were longer than six-instar females at adulthood. Interestingly, the total developmental period from hatching to adulthood was similar for lab-reared seven-instar and six-instar females. In the lab, most males (91%) underwent 6 instars, with the remaining 9% following a five-instar pattern. By the 4th instar, differences between the sexes began to appear. From the 4th instar onwards, females typically took less time than males to reach each instar. From the 5th instar onwards, females were longer than the males, and were longer as adults. Variation in developmental pattern (number of instars) was evident among siblings from the same ootheca; such intra-clutch variability in number of instars may be a bet-hedging strategy by ovipositing females in a variable environment. The laboratory data allowed for the detection of six-instar and seven-instar patterns among the field-collected females. The field-collected data suggest that females undergoing 6 nymphal instars reach adulthood later in the season, and at smaller body size, than seven-instar females.

Stagmomantis is a remarkable genus within the Mantodea, being relatively species-rich and geographically widespread. Yet, the number of species within the genus remains curiously unresolved. The present synoptic review surveys the literature on Stagmomantis to identify named species for which scientific consensus exists, as well as to summarize basic biological information for each species, including geographic distribution, morphological features, and sex-specific biometric data. The review identifies 23 consensus taxa within Stagmomantis: 22 separate species, with one of these species, S. montana, split into two subspecies (S. m. montana and S. m. sinaloae). The review indicates morphological features that may prove to be diagnostic for a given species, particularly when examined in conjunction with male genitalia. Such features include dark spots on the anterior femur (S. amazonica, S. centralis, S. marginata, S. nahua, S. venusta, S. vicina), spines or denticulations on the anterior coxa (S. colorata, S. montana montana, S. parvidentata, S. theophila), and dark bands on abdominal tergites (S. californica, S. colorata, S. domingensis). Color variation of certain features with respect to body coloration, such as stigma coloration and body and leg markings, requires more attention. Information on life history, reproduction, and ecology are summarized, particularly for temperate populations of S. carolina and S. limbata. While the 23 consensus taxa represent a robust appraisal of the existing literature, some taxonomic uncertainties remain. The status of two species are somewhat unclear (S. marginata and S. tolteca), calling for taxonomic evaluation. Furthermore, proposed within-genus groupings deserve examination, as do possible subdivisions within some species (e.g., S. limbata, S. parvidentata). Information on basic morphology and biometry remains incomplete for nearly all species. Extreme examples are S. amazonica, S. costalis, and S. paraensis, for which females have not been described. Live animal research on life history, behavior, and ecology is needed for all species, with the possible exceptions of S. carolina and S. limbata. By reconciling species assignments and consolidating biological information for the 23 consensus taxa, this synoptic review promises to guide subsequent systematic and phylogenetic investigations of the genus Stagmomantis.

Body size is an important feature of organisms, influencing many components of life history and fitness, such as feeding success and reproductive output. Body size is considered especially salient for solitary predators, whose food intake hinges on individual predation success, which in turn is often driven by the relative sizes of predator and prey. The current study examined intraspecific variation in adult female length and its fitness consequences in a solitary predator, the praying mantid Stagmomantis limbata Hahn. Through a 5-yr integration of observational and experimental work in the field and captivity, we investigated the relationship between female pronotum length and prey size, diet breadth, male attraction, and measures of egg production (fecundity and ootheca mass). We found that longer females ate longer prey in the field and showed greater breadth of prey size than shorter females. Longer females did not necessarily feed at higher rates in the field, as measured by the rate of abdominal expansion. Female length failed to show significant effects on male attraction or on the incidence of cannibalism. Longer females had higher fecundity (mature eggs in body at death) and laid heavier oothecae than shorter females. In nature, longer females consistently emerged as adults earlier in the season than shorter females. Shorter female adults emerged when feeding rates were higher in the field, suggesting an incidental ecological benefit of shorter adult size.

Males of the spider Pisaura mirabilis offer prey items as nuptial gifts to females. While gift giving in this species has received attention in captivity, the ecological context of these gifts remains largely unknown. First, we examine the occurrence of gift carrying by males in nature. Field data reveal that gift-carrying males are frequent in nature (40% of captured males), and that all gifts contain fresh arthropod prey. Gift mass was positively correlated with the longest diameter of the gift. Thus, males do not appear to 'cheat' by inflating their gifts with inedible items, air or loosely wrapped silk. Second, we examine two ecological costs to gift-carrying males: the effects of gifts on male running speed and male fighting success. Gift carrying reduced male running speed, but did not affect male fighting success in male-male contests. The former result is the first demonstration of a transportation cost associated with gift carrying in an arthropod. (c) 2012 The Association for the Study of Animal Behaviour. Published by Elsevier Ltd. All rights reserved.

Sexual conflict is implicated in the evolution of nuptial feeding. One function of nuptial gifts lies in mating effort, where the female’s eating of the gift reduces her likelihood of prematurely terminating sperm transfer. We test several ideas regarding sexual conflict in the nuptially feeding wood cricket Nemobius sylvestris. In this cricket, males pass two kinds of spermatophores to females: spermless microspermatophores and larger sperm-filled macrospermatophores. Females may palpate the males’ forewing secretions as a possible additional form of nuptial feeding. We manipulated male mobility and female feeding regime to examine the effects on spermatophore transfer, macrospermatophore attachment duration, and palpations of the males’ forewings. Neither male confinement nor female feeding regime affected the occurrence of macrospermatophore transfer. Males transferred the macrospermatophore sooner to low-food females than to high-food females. Males that were freely mobile (unconfined and sham treatments) had longer macrospermatophore attachment durations than confined males, while female feeding regime did not affect attachment duration. The overall occurrence of female palpation was not significantly affected by female feeding regime. However, high-food females were more likely to perform short palpations before microspermatophore transfer, while low-food females were more likely to palpate after macrospermatophore transfer. Sexual conflict is evident in that males appear to guard against premature removal of the sperm-filled macrospermatophore. Low-food females appear to facilitate the early transfer of the macrospermatophore, while being more likely to perform relatively long post-insemination palpations than better-fed females.

We develop a per-recruit model for the management of the California market squid (Loligo opalescens) fishery. Based on recent confirmation of determinate fecundity in this species, we describe how catch fecundity (i.e., eggs remaining in the reproductive tracts of harvested females) can be used to simultaneously infer fishing mortality rate along with management reference points such as yield-per-recruit, spawned eggs-per-recruit, and proportional egg escapement. Rates of mortality and egg laying have important effects on these reference points. Somewhat surprisingly, increasing the rate of natural mortality decreased spawned eggs-per-recruit while increasing proportional egg escapement. Increasing the rate of egg laying increased both spawned eggs-per-recruit and egg escapement. Other parameters, such as the maturation rate and gear vulnerability of immature females, affected the reference points. In actual practice, the influence of these parameters for immature squid may go undetected if immature squid are excluded from analysis of the catch. Application of this model to routine management is feasible but requires refinement of sampling procedures, biological assumptions, and model parameters. This model is useful because it is grounded on empirical data collected relatively inexpensively from catch samples (catch fecundity) while allowing for the simultaneous calculation of instantaneous fishing mortality rate and egg escapement.

Recent behavioral and phylogenetic studies have revived appreciation for variation in behavior and morphology in the Mantodea, both within and between species. In the bordered mantid Stagmomantis limbata, variation in the occurrence of sexual cannibalism is influenced by ecological factors, such as female feeding regime. Female morphology, such as prontoum length, is affected by the environment, with pronotum length decreasing with the date of adult emergence in field populations. This variability in female length within a season produces a broad range of degree of sexual dimorphism (male length/female length x 100%), from 50% to over 90%. Interspecific variation in behavior (sexual cannibalism) and morphology (body length), while based on a somewhat nascent dataset, is considered in a phylogenetic framework.

1. Female feeding regime exhibited a cascade of effects on reproductive biology and behaviour in the mantid Stagmomantis limbata (Hahn). 2. Well-fed females (High diet) consistently attained greater body mass, thicker abdomens, and higher fecundity than food-limited females (Low diet) in four annual generations. Dorso-ventral abdominal thickness strongly correlated with fecundity. 3. In an experiment in captivity, Low diet females were more likely to cannibalize males than High diet females. 4. High diet females attracted more males than Low diet females in several contexts. In terms of long-range attraction, caged High diet females attracted more males in the field. In terms of short-range attraction, males preferentially mounted and copulated with High diet females in captive paired choice trials. In naturally-occurring pairs in the field, a preference for females with thick abdomens was evident. These results point to two possible explanations: male choice for well-fed females and state-dependent female pheromone emission. 5. Two years of field data indicate considerable variation in female feeding success, as measured by abdominal thickness. Average feeding success in nature appears to be relatively high, when comparing the rate of abdominal expansion in the field to captive females maintained on High diets. 6. In the field, nearly all mounts and copulations occurred in September in both years, when female feeding success is expected to be high. If mating activity occurs during a window of high female feeding success, so as to reduce the risk of cannibalism for males, then the female feeding regime may be implicated in the phenology of mating activity in cannibalistic species.