The effects of body size on mating success and duration of copulation were investigated in Pyrrhocoris apterus. Under laboratory conditions relative mating success of small and large males was investigated in groups of 2 males (majority sex) : 1 female (minority sex). Large males were recorded significantly more often in copulation than small males when the female was large but not when the female was small. This was also the case when the group size was 24 males : 12 females or population density decreased by increasing the area of the experimental arena. In groups of 2females : 1 male, large females were recorded in copulation significantly more often than small females when the male was large but not when the male was small. Proportion of individuals of the minority sex that copulated was similar for males and females, regardless of body size. The average duration of copulation was similar for small and large males, but shorter for small than large females. The difference in the duration of copulation of small and large females was greater when it was with small rather than large males. The prolonged guarding of large females by small males may be explained by a trade-off between increasing the probability of inseminating an uneasily accessible high quality partner and copulating with more females.
There are records of glands that produce sexual pheromones that are released into the environment or applied directly on sexual partners. Within Opiliones (Arachnida), several harvestmen in the suborder Laniatores have sexually dimorphic glands on legs I and IV, the mode of use of which is recorded only in two species but their function is unknown: while walking, males rub the glands against the substrate or against their body. Here we test an alternative and non-exclusive hypothesis that the glands present on the legs of male Gryne perlata (Cosmetidae) produce contact pheromones used in mating. We predicted that males would touch the females with the gland openings or with other male body parts previously rubbed by these glands. We also predicted that there are chemoreceptors on those parts of the females where males touch them. We analyzed 13 videos of G. perlata mating, a species in which the males have glands on legs I and IV of unknown function. We also analyzed 14 videos of Discocyrtus pectinifemur (Gonyleptidae) mating as a control, a species that lacks these glands. Finally, we looked for chemoreceptors on the legs of female G. perlata using a scanning electron microscope. During copulation, males of both species rubbed the legs of females with their first pair of legs, but not with the regions of these legs where the openings of the glands are. The fourth pair of legs were only used to support the body. Rubbing other body parts of the female by males with their glands was not observed during mating. Setae on the legs of the female did not have tip pores and therefore do not seem to be chemoreceptors. We therefore did not find any evidence that these sexually dimorphic glands in G. perlata release contact pheromones during mating., Jéssica M. Dias, Rodrigo H. Willemart., and Obsahuje bibliografii
In the laboratory, not all females of the seed bug Lygaeus simulans Deckert, 1985, produced fertilized eggs after copulation: 26.7% of the females were not inseminated and 5% were inseminated but did not lay fertilized eggs; only in 40% of the couples did copulation result in fertile eggs. The remaining 28.3% of couples refrained from mating. Duration of copulation was associated with insemination and fertilization: (i) fertile eggs were produced by only one couple that copulated for less than 60 min and all those that copulated for more than 360 min, (ii) probability of fertilization increased steadily with duration of copulation between 60 and 360 min, and (iii) duration of copulation was significantly different for couples that showed different insemination status.
A possible morphological explanation for this rime dependency was revealed by examining the genitalia of 69 couples freeze-fixed in copula after different periods in copulation. Because of the intricate structure of the genitalia in L. simulans, a male takes a long time to manoeuver its intromittent organ into the narrow insemination duct of the female. Only if completely inserted is the tip of the intromittent organ close enough for successful ejaculation of sperm into the spermatheca. The freeze-fixing experiment revealed that it usually took the male more than 30 min to locate the entrance to the insemination duct and another 30 min for full penetration. This explains why copulations that lasted less than 60 min failed, since insemination began only after intromission was complete.
The experiments, therefore, indicated that there is a relationship between the complex morphology of the genitalia and the low rates of insemination and fertilization in L. simulans., Thomas Micholitsch, Peter Krügel, Günther Pass, 7 obrázků, 1 tab., and Lit.
Accurate Batesian mimicry is known to impose constraints on some traits of the mimic, such as foraging or reproductive behaviour. It is not known whether life-history traits of inaccurate Batesian mimics are constrained as well. We studied selected life-history traits of three spider species, Liophrurillus flavitarsis, Phrurolithus festivus (both Corinnidae), and Micaria sociabilis (Gnaphosidae), that are inaccurate mimics of ants. Namely, we were interested in how myrmecomorphy (ant-like resemblance) constrains their circadian activity, trophic niche and reproductive behaviour. The spiders were found to have diurnal activity like their models, whereas their close relatives have nocturnal activity. The three mimics do not catch ants, nor do they use food resources of ants, but catch various tiny invertebrates that occur in the vicinity of their models. Their trophic niche seems to be constrained by occurrence among ants. Absence of courtship and long lasting copulation, in a position that does not provide protective resemblance, do not seem to be constrained by mimicry in the three species. Comparative analysis of fecundity in mimetic and non-mimetic spiders showed that clutch size is also not constrained. Unlike in accurate mimics, life-history traits of inaccurate myrmecomorphs appear not to be constrained. and Stano Pekár, Martin Jarab.
The mating behaviour of Pyrrhocoris apterus in the laboratory is well studied, but little is known about it under natural conditions. In natural populations in Central Europe, overwintered adults start copulating in March and continue until their death. Caged females, kept under natural conditions in the permanent presence of males, copulated repeatedly. Their mating activity increased sharply until early April, then very slowly until the end of June and then declined as the females die-off. Half of copulations were short (< 5 h) and only 9% were longer than 1 day. By contrast, in natural populations, mating activity (percentage of individuals involved in copula) reached its maximum in April and then decreased until early July, when the overwintered adults die. The decline in mating frequency (percentage of adults involved in copula) was associated with a decrease in the availability of receptive females towards the end of the mating period. For a female, repeated copulation is necessary because sperm is nearly depleted after insemination of 3-5 egg batches.