Genitalic stridulation during copulation in a species of crane fly, Tipula (Bellardina) sp. (Diptera: Tipulidae) / Estridulación genital durante la cópula en una especie de mosca grulla, Tipula (Bellardina) sp. (Dípteros: Tipulidae)

The male genitalia of many animal groups have elaborate and species-specific forms. One hypothesis  to explain why this is so is that male genitalia function as stimulatory devices that are under sexual selection by cryptic female choice. This report is based on a videotaped observation of a single male of an unidentified species of Tipula (Bellarina) from San José Province, Costa Rica. A male crane fly stridulated (produced vibrations) during copulation using sustained and stereotyped movements of file and scraper structures on his genitalia. Males of related species have similar file and scraper structures on their genitalia, suggesting that they probably also stridulate during copulation. Rev. Biol. Trop. 57 (Suppl. 1): 251-256. Epub 2009 November 30.

Un macho de Tipula (Bellardina) sp. estriduló (produjo vibraciones) por medio de movimientos estereotipados de estructuras de sus órganos genitales durante varios minutos de la cópula. Los machos de algunas especies relacionadas poseen estructuras similares, lo cual sugiere que también estridulan durante la cópula.

Seasonal patterns of parasitism of the tropical spiders Theridion evexum (Araneae, Theridiidae) and Allocyclosa bifurca (Araneae, Araneidae) by the wasps Zatypota petronae and Polysphincta gutfreundi (Hymenoptera, Ichneumonidae)

The rates of parasitism of Theridion evexum by the parasitoid wasp Zatypota petronae, and Allocyclosa bifurca by Polysphincta gutfreundi, were followed for two years. Parasitism of T. evexum was very low (mean 1.39+1.8%), and restricted to nearly seven months of the year. Parasitism of A. bifurca was higher (mean 7.8+7.6%), and did not show a seasonal pattern. Reproduction of the host spider T. evexum was highly seasonal, with only one, highly coordinated generation per year, while adults of A. bifurca were present year round. Short-term autocorrelation on parasitism rates over time at different sites suggest that P. gutfreundi tend to return to the same sites to hunt hosts over periods of a few weeks. Rev. Biol. Trop. 56 (2): 749-754. Epub 2008 June 30.

Las tasas de parasitismo de Theridion evexum por la avispa parasitoide Zatypota petronae y de Allocyclosa bifurca por Polysphincta gutfreundi fueron estudiadas durante dos años. El parasitismo en T. evexum fue muy bajo (promedio 1.39+1.8%) y restringido a aproximadamente siete meses del año. El parasitismo en A. bifurca fue más alto (promedio 7.8+7.6%) y no mostró un claro patrón estacional. La reproducción de la araña hospedera T. evexum fue muy estacional, con solamente una generación por año, mientras que los adultos de A. bifurca estuvieron presentes todo el año. Autocorrelaciones de las tasas de parasitismo entre censos consecutivos en diferentes sitios sugiere que P. gutfreundi tiende a retornar a los mismos sitios para parasitar las arañas hospederas durante algunas semanas.

Fitting together: copulatory linking in some Neotropical Chrysomeloidea

Copulatory linking of male and female genitalic structures in 11 Neotropical species of Chrysomelidae and one species of Megalopodidae was studied by freezing and then dissecting pairs of beetles in copula. In Megalopus armatus (Megalopodidae) the male has a long endophallus with complex membranous protuberances and a terminal flagellum that probably reaches the spermatheca. In the subfamily Eumolpinae the females have telescoping ovipositors through which the male endophalli pass, reaching to or near the mouth of the spermathecal duct. A long thin flagellum is probably inserted into the spermathecal duct. The male endophalli are braced inside the female using various structures, including two pairs of lateral appendages and apical appendages (both lateral pairs sclerotized in Colaspis sanjoseana and only the basal pair in Brachypnoea irazuensis), a pair of membranous swellings (in Metaxyonycha amasia), and apical microspicules on the endophallus (in Xanthonia). In the subfamily Galerucinae, males of Metrioidea and Diabrotica (tribe Galerucini) have relatively short endophalli ornamented with sclerotized hooks, spines and needles. In Metrioidea elongata the long needle-like endophallic spines of the male were erected inside the female and penetrated the wall of her bursa. In the tribe Alticini, the male endophallus is very short and does not enter the female in two species, Alagoasa gemmata and Walterianella sp. Instead, the apical parts of the female bursae were everted, and were clamped by sclerites of the male median lobe. The male genitalia of Plectrotetra hirsuta reached deep into the female, to the median oviduct, far beyond the mouth of the spermathecal duct. Both rigid and membranous structures meshed in complex ways. When these observations are combined with published descriptions of mating in other Chrysomelidae, the great diversity of copulatory morphology in these families comes into sharper focus.

Se describen los coajustes mecánicos entre las estructuras genitales de machos y hembras de 11 especies neotropicales de Chrysomelidae y una especie de Megalopodidae. Las parejas fueron congeladas durante la cópula y después disectadas. En Megalopus armatus (Megalopodidae) el macho tiene un endofalo largo, con protuberancias membranosas complejas, y un flagelo terminal que probablemente penetra el largo del ducto de la espermateca hasta el lumen de la espermateca. En la subfamilia Eumolpinae, las hembras tienen ovipositores telescópicos, a través de los cuales los endofali de los machos pasan para llegar hasta o cerca a la boca del ducto de la espermateca. Es probable que el largo y delgado flagelo se inserta en el ducto de la espermateca. El endofalo del macho se apoya dentro de la hembra por varias estructuras, las cuales incluyen dos pares de apéndices laterales y apéndices apicales (ambos pares laterales son esclerotizados en Colaspis sanjoseana, únicamente el par basal en Brachypnoea irazuensis), un par de hinchamientos membranosos (en Metaxyonycha amasia), y espículas apicales sobre el endofalo (en Xanthonia). En la subfamilia Galerucinae, los machos de Metrioidea y Diabrotica (tribu Galerucini) tienen endofalos relativamente cortos, pero adornados con varios ganchos, espinas y agujas. En Metrioidea elongata las largas espinas endofálicas se abrieron dentro de la hembra, y penetraron las paredes de su bursa. En la tribu Alticini, el endofalo del macho de dos especies, Alagoasa gemmata y Walterianella sp., es muy corto y no entró al cuerpo de la hembra. En su lugar, la parte apical de la bursa de la hembra fue evertida, y fue agarrada por escleritos del lóbulo mediano del macho. Los genitales de Plectrotetra hirsuta penetraron profundamente en la hembra, llegando probablemente hasta el oviducto mediano, más profundo que la boca del ducto de la espermateca. Estructuras de...

The function of female resistance behavior: intromission by male coercion vs. female cooperation in sepsis flies (Diptera: Sepsidae)

Female resistance behavior that occurs prior to intromission does not by itself imply forced copulation. Such behavior may function instead as a test of the male in order to favor some males over others, or to induce the male to desist. Thus, male persistence and forcefullness may sometimes be better described as persuasion rather than coercion. Under the persuasion hypothesis, the male only gains intromission due to an active response of the female. Under the coercion hypothesis, male and female are opposed in a physical battle which the female loses if copulation occurs. In species in which males are morphologically incapable of forcing intromission without active female cooperation (I argue here that this is probably a very common situation), data on the behavioral and ecological context in which resistance occurs can distinguish between the two possibilities. Partially congruent functions of resistance, seen from the female point of view, are female resistance to screen (male persuasion), and female resistance to avoid males non-selectively (male coercion). Sepsis flies illustrate these ideas. Females often struggle energetically in apparent attempts to dislodge mounted males and to prevent intromission, and males grasp females with powerful species-specific structures on their front legs and genitalia. This suggests the possibility of coerced intromission. But behavioral and morphological evidence demonstrate that active female cooperation occurs at the moment of intromission, and that males are probably dependent on this cooperation because they are not morphologically equipped to force their genitalia into those of an uncooperative female. Despite the impression from previous publications, male insects in general may seldom be able to achieve intromission by genitalic force. The species-specific forms of the grasping genitalia of male sepsis are probably not the result of an evolutionary arms race between coercive males and unselectively resistant females.