Nephila clavipes spiders (Araneae: Nephilidae) keep track of captured prey counts: testing for a sense of numerosity in an orb-weaver.

Nephila clavipes golden orb-web spiders accumulate prey larders on their webs and search for them if they are removed from their web. Spiders that lose larger larders (i.e., spiders that lose larders consisting of more prey items) search for longer intervals, indicating that the spiders form memories of the size of the prey larders they have accumulated, and use those memories to regulate recovery efforts when the larders are pilfered. Here, we ask whether the spiders represent prey counts (i.e., numerosity) or a continuous integration of prey quantity (mass) in their memories. We manipulated larder sizes in treatments that varied in either prey size or prey numbers but were equivalent in total prey quantity (mass). We then removed the larders to elicit searching and used the spiders' searching behavior as an assay of their representations in memory. Searching increased with prey quantity (larder size) and did so more steeply with higher prey counts than with single prey of larger sizes. Thus, Nephila spiders seem to track prey quantity in two ways, but to attend more to prey numerosity. We discuss alternatives for continuous accumulator mechanisms that remain to be tested against the numerosity hypothesis, and the evolutionary and adaptive significance of evidence suggestive of numerosity in a sit-and-wait invertebrate predator.

Spiders avoid sticking to their webs: clever leg movements, branched drip-tip setae, and anti-adhesive surfaces.

Orb-weaving spiders construct webs with adhesive silk but are not trapped by it. Previous studies have attributed this defense to an oily coating on their legs that protects against adhesion or, more recently, to behavioral avoidance of sticky lines. The old evidence is very weak, however, and the behavioral avoidance explanation is inadequate because orb-weavers push with their hind legs against sticky lines hundreds or thousands of times during construction of each orb and are not trapped. Video analyses of behavior and experimental observations of isolated legs pulling away from contact with sticky lines showed that the spider uses three anti-adhesion traits: dense arrays of branched setae on the legs that reduce the area of contact with adhesive material; careful engagement and withdrawal movements of its legs that minimize contact with the adhesive and that avoid pulling against the line itself; and a chemical coating or surface layer that reduces adhesion.

Copulatory behaviour and the process of intromission in Anastrepha ludens (Diptera: Tephritidae).

Complex genitalia occur in many arthropods and in some species extreme female morphologies lead to serious mechanical difficulties for males. Tephritid flies offer examples of such complex genitalia. Because of their economic importance and the extensive use of sterile male releases for tephritid control in Texas and Mexico, studies have been done on various aspects of their basic reproductive biology, but the process of intromission has received little attention. The distiphallus of the male of Anastrepha ludens is complex. One membranous sac on the distiphallus is capable of rhythmic cycles of inflation and deflation. Inflations of the sac near the base of the distiphallus probably help propel the aedeagus deeper into the female along with stiffening of the basiphallus and may drive the genital rod (which does not transfer sperm) into the ventral receptacle. We were unable to establish an association between some of the behaviours displayed by males during mating and intromission process.

Copulatory behaviour and the process of intromission in Anastrepha ludens (Diptera: Tephritidae)

Complex genitalia occur in many arthropods and in some species extreme female morphologies lead to serious mechanical difficulties for males. Tephritid flies offer examples of such complex genitalia. Because of their economic importance and the extensive use of sterile male releases for tephritid control in Texas and Mexico, studies have been done on various aspects of their basic reproductive biology, but the process of intromission has received little attention. The distiphallus of the male of Anastrepha ludens is complex. One membranous sac on the distiphallus is capable of rhythmic cycles of inflation and deflation. Inflations of the sac near the base of the distiphallus probably help propel the aedeagus deeper into the female along with stiffening of the basiphallus and may drive the genital rod (which does not transfer sperm) into the ventral receptacle. We were unable to establish an association between some of the behaviours displayed by males during mating and intromission process. Rev. Biol. Trop. 59 (1): 291-297. Epub 2011 March 01.

En muchos artrópodos, se observan genitales complejos; la morfología extrema en las hembras podría conducir a serios problemas mecánicos para los machos (Kamimura & Matsuo 2001). Las moscas tefrítidas tienen ejemplos de tales órganos genitales complejos. Debido a su importancia económica y la amplia utilización de machos estériles para el control biológico en Texas y México, se han realizado estudios sobre diversos aspectos de su biología reproductiva, pero el proceso de penetración ha recibido muy poca atención. El distiphallus de los machos de Anastrepha ludens es complejo. Un saco membranoso en el distiphallus es capaz de realizar ciclos rítmicos de inflación y deflación. El inflado de la bolsa cerca de la base del distiphallus, junto con la rigidez del basiphallus probablemente ayuda a impulsar el edeagus más profundamente en la hembra y orientar la vara genital (que no transfiere esperma) en la región del receptáculo ventral. No pudimos establecer una asociación entre algunas de las conductas mostradas por los machos durante el apareamiento y el proceso de intromisión.

Substrate vibrations in the scorpion Centruroides margaritatus (Scorpiones: Buthidae) during courtship / Vibraciones del sustrato en el escorpión Centruroides margaritatus (Scorpiones: Buthidae) durante el cortejo

Mating behavior in Centruroides margaritatus, as in other scorpion species, includes a series of rapid rocking or shaking movements of the male ("juddering"). It has been suggested that substrate vibrations are generated by juddering and that females respond to them by approaching the male, but its functional significance remains little studied. For the first time, substrate vibrations produced by males during courtship in Centruroides margaritatus are documented. The male started juddering after his first physical contact with the female and only one type of male vibratory signal was registered. The signal is produced during a series of rapid shaking of the male’s body from front to rear and consists of multiple short pulses. Each pulse is called a judder and several judders "a series". The average duration of each judder was 0.018±0.009s (n=50) with an interval of 0.028±0.013s (n=50); the average duration of each series of judders was 4.2±3.5s with an interval between series of 3.5±6.3s and a rate of 0.21±0.17 series per second. The females responded in 72% of the time to the males juddering. Rev. Biol. Trop. 57 (Suppl. 1): 267-274. Epub 2009 November 30.

El comportamiento de apareamiento en Centruroides margaritatus como en otras especies del escorpiones, incluye una serie de oscilaciones rápidas hacia adelante y hacia atrás del cuerpo del macho (juddering). Se ha especulado que tales oscilaciones generan vibraciones en el substrato y las hembras pueden responder a ellas aproximándose al macho, pero su significado funcional sigue siendo poco estudiado. Por primera vez, las vibraciones del substrato producidas por los machos durante el comportamiento de cortejo de Centruroides margaritatus son documentadas. El macho comenzó las vibraciones después de su primer contacto físico con la hembra y sólo se registró un tipo de señal vibratoria. La señal se produce durante una serie de rápidas sacudidas del cuerpo del macho de adelante hacia atrás y se compone de múltiples pulsos cortos. La duración media de cada pulso fue 0.018±0.009s (n = 50) con un intervalo de 0.028±0.013s (n=50); la duración media de cada serie de pulsos fue de 4.2±3.5s, con un intervalo entre las series de 3.5±6.3s y una tasa de 0.21±0.17 serie por segundo. Las hembras respondieron en un 72% del tiempo a las sacudidas de los machos. Se discute acerca de su posible función como señal.

Acoustic courtship songs in males of the fruit fly Anastrepha ludens (Diptera: Tephritidae) associated with geography, mass rearing and courtship success / Cantos acústicos de cortejo en machos de la mosca de la fruta Anastrepha ludens (Diptera: Tephritidae) asociados con geografía, crianza masiva y éxito de cortejo

The Sterile Insect Technique (SIT) has been used successfully to control or eradicate fruit flies. The commonly observed inferiority of mass-reared males, compared with wild males, when they are paired with wild females, is apparently due to their inadequate courtship. Anastrepha ludens males produce two types of wing vibration during courtship and mating, the "calling sound" and the "premating or precopulatory sound". There were clear differences in the calling songs between successful and unsuccessful courtships in sterile (irradiated) and fertile Mexican flies. Among sterile flies, successful males produce longer buzzes, shorter interpulses and a higher power spectrum in the signal. Fertile flies showed the same trend. For mating songs a significant difference occurred in two parameters: power spectrum between sterile and fertile flies with respect to the type of song, and the signal duration and intensity were greater in non-irradiated flies. Calling songs of wild flies compared with laboratory grown flies from Mexico had shorter interpulses, longer pulses, and a greater power spectrum. However, in the case of premating songs, the only difference was in the intensity, which was significantly greater in wild males. An unexpected result was not observing pulses during pheromone deposition in wild males from Costa Rica. Comparing the premating songs of wild flies from Costa Rica and Mexico, no significant differences were observed in the duration, and the intensity of the signal was slightly greater in flies from Mexico. Rev. Biol. Trop. 57 (Suppl. 1): 257-265. Epub 2009 November 30.

La técnica estéril del insecto (SIT) se ha utilizado con éxito para controlar o para suprimir las moscas de fruta y su impacto en los cultivos. La inferioridad comúnmente observada de machos criados masivamente, comparada con los machos silvestres, cuando se aparean con las hembras silvestres es al parecer debido a su inadecuado cortejo. Los machos de Anastrepha ludens producen dos tipos de vibraciones del ala durante cortejo y el apareamiento, una de "llamada" y "el sonido de pre-apareamiento o precopulatorio". Se encontraron diferencias claras en las canciones de llamada entre los cortejos exitosos y no exitosos en moscas estériles y fértiles de Mexico. En las moscas estériles, los machos exitosos producen zumbidos más largos, interpulsos más cortos y un espectro de una energía más alta en la señal. Las moscas fértiles mostraron la misma tendencia. Para las canciones precopulatorias hay diferencias significativas en dos parámetros: el espectro de energía entre las moscas irradiadas y no irradiadas también observadas con respecto al tipo de canción, y la duración y la intensidad de la señal fueron mayores en moscas no irradiadas. Las canciones de llamada de las moscas silvestres comparadas con las de laboratorio de México tenían interpulsos más cortos, pulsos más largos, y un mayor espectro de energía. Sin embargo, en el caso de canciones precopulatorias, la única diferencia estaba en la intensidad, que era perceptiblemente mayor en machos silvestres. Un resultado inesperado fue no observar canciones de llamada durante la deposición de la feromona en machos silvestres de Costa Rica. Al comparar las canciones precopulatorias de moscas silvestres de Costa Rica y de México, no se observó ninguna diferencia significativa en la duración, ni en la intensidad de la señal.

Experimental demonstration of possible cryptic female choice on male tsetse fly genitalia.

A possible explanation for one of the most general trends in animal evolution - rapid divergent evolution of animal genitalia - is that male genitalia are used as courtship devices that influence cryptic female choice. But experimental demonstrations of stimulatory effects of male genitalia on female reproductive processes have generally been lacking. Previous studies of female reproductive physiology in the tsetse fly Glossina morsitans suggested that stimulation during copulation triggers ovulation and resistance to remating. In this study we altered the form of two male genital structures that squeeze the female's abdomen rhythmically in G. morsitans centralis and induced, as predicted, cryptic female choice against the male: sperm storage decreased, while female remating increased. Further experiments in which we altered the female sensory abilities at the site contacted by these male structures during copulation, and severely altered or eliminated the stimuli the male received from this portion of his genitalia, suggested that the effects of genital alteration on sperm storage were due to changes in tactile stimuli received by the female, rather than altered male behavior. These data support the hypothesis that sexual selection by cryptic female choice has been responsible for the rapid divergent evolution of male genitalia in Glossina; limitations of this support are discussed. It appears that a complex combination of stimuli trigger female ovulation, sperm storage, and remating, and different stimuli affect different processes in G. morsitans, and that the same processes are controlled differently in G. pallidipes. This puzzling diversity in female triggering mechanisms may be due to the action of sexual selection.

Experimental modifications imply a stimulatory function for male tsetse fly genitalia, supporting cryptic female choice theory.

One of the most sweeping of all patterns in morphological evolution is that animal genitalia tend to diverge more rapidly than do other structures. Abundant indirect evidence supports the cryptic female choice (CFC) explanation of this pattern, which supposes that male genitalia often function to court females during copulation; but direct experimental demonstrations of a stimulatory function have been lacking. In this study, we altered the form of two male genital structures that squeeze the female's abdomen rhythmically in Glossina pallidipes flies. As predicted by theory, this induced CFC against the male: ovulation and sperm storage decreased, while female remating increased. Further experiments showed that these effects were due to changes in tactile stimuli received by the female from the male's altered genitalia, and were not due to other possible changes in the males due to alteration of their genital form. Stimulation from male genital structures also induces females to permit copulation to occur. Together with previous studies of tsetse reproductive physiology, these data constitute the most complete experimental confirmation that sexual selection (probably by CFC) acts on the stimulatory properties of male genitalia.

Copulation behaviour of Glossina pallidipes (Diptera: Muscidae) outside and inside the female, with a discussion of genitalic evolution.

If species-specific male genitalia are courtship devices under sexual selection by cryptic female choice, then species-specific aspects of the morphology and behaviour of male genitalia should often function to stimulate the female during copulation. The morphology and behaviour of the complex, species-specific male genitalia of the tsetse fly, Glossina pallidipes Austen, were determined from both direct observations and dissections of flash-frozen copulating pairs; we found that some male genitalic traits probably function to stimulate the female, while others function to restrain her. The male clamps the ventral surface of the female's abdomen tightly with his powerful cerci. Clamping does not always result in intromission. Clamping bends the female's body wall and her internal reproductive tract sharply, posteriorly and dorsally, and pinches them tightly. The male performed sustained, complex, stereotyped, rhythmic squeezing movements with his cerci that were not necessary to mechanically restrain the female and appeared instead to have a stimulatory function. Six different groups of modified setae on and near the male's genitalia rub directly against particular sites on the female during squeezing. The designs of these setae correlate with the force with which they press on the female and the probable sensitivity of the female surfaces that they contact. As expected under the hypothesis that these structures are under sexual selection by female choice, several traits suspected to have stimulatory functions have diverged in G. pallidipes and its close relative, G. longipalpis. Additional male non-genitalic behaviour during copulation, redescribed more precisely than in previous publications, is also likely to have a courtship function. The elaborate copulatory courtship behaviour and male genitalia may provide the stimuli that previous studies showed to induce female ovulation and resistance to remating.

Sexual behavior of mutant strains of the medfly Ceratitis capitata (Diptera: Tephritidae)

Males of the mutant strains (blind, vestigal-winged) of the Mediterranean fruit fly (medfly), Ceratits capitata (Wiedmann) showed differences in behavior compared with control (mass-reared) males. Mutant males made fewer mating attempts and achieved fewer matings than control males. Vestigal-winged females copulated less frequently with both mutants. Blind males climbed rather than jumped onto females and copulated in very low numbers compared with control and vestigal males. Blind females copulated normally with control, males and in very low numbers with both types of mutant males.

Sexual behavior of mutant strains of the medfly Ceratitis capitata (Diptera: Tephritidae).

Males of the mutant strains (blind, vestigal-winged) of the Mediterranean fruit fly (medfly), Ceratits capitata (Wiedmann) showed differences in behavior compared with control (mass-reared) males. Mutant males made fewer mating attempts and achieved fewer matings than control males. Vestigal-winged females copulated less frequently with both mutants. Blind males climbed rather than jumped onto females and copulated in very low numbers compared with control and vestigal males. Blind females copulated normally with control, males and in very low numbers with both types of mutant males.

Genetic and environmental effects on wing polymorphisms in two tropical earwigs (Dermaptera: Labiidae).

The tropical earwigs Paralabella dorsalis and Pseudomarava prominensis are polymorphic for wings in both sexes. An individual's chances of being winged are influenced by whether its parents were winged, by its own sex, and by its nymphal nutrition (at least in P. dorsalis). Wingless females of P. dorsalis lived longer, started ovipositing ealier, and laid slightly larger clutches.