José Tormos

Female-female attraction influences nest establishment in the digger wasp Stizus continuus (Hymenoptera: Crabronidae)

Although digger wasps are good models for the study of nest site selection, the behaviour of females in relation to time of nest establishment has rarely been considered despite this being the key to discrimination between substrate availability-based and a female attraction-based selection. We carried out a study on nest establishment by the digger wasp Stizus continuus (Klug), giving to all nests dug by the wasps both spatial (nearest neighbour distance to nests, proximity of vegetation, soil hardness) and temporal (day of excavation) attributes. Stizus continuus females dug more nests under bush edges, where the soil was much softer. There was no tendency for females to maximize distance between nests at the moment of establishment. On the contrary, as shown by different nearest neighbour statistics, females preferentially tend to dig close to conspecific nests (if one considers both the whole study area and two subareas free of vegetation and at different times of the nesting season). Moreover, those nests that were active (still provisioned) attracted more females than the inactive nests at the moment of nest establishment. We conclude that female S. continuus are attracted by conspecifics at the moment of nest establishment and that clumped patterns of nests are a result of such social attraction rather than a result of limited available substrate; moreover, such attraction could be better detected when comparative analyses are employed and best at a multiple-scale view.

The Preimaginal Phases and Development of Pachycrepoideus vindemmiae (Hymenoptera, Pteromalidae) on Mediterranean Fruit Fly, Ceratitis capitata (Diptera, Tephritidae)

The development and morphology of the immature phases of Pachycrepoideus vindemmiae (Rondani, 1875) (Hymenoptera, Pteromalidae) are described from a laboratory rearing culture maintained on Ceratitis capitata (Wiedemann, 1824) (Diptera, Tephritidae) using microscopic techniques, including light and scanning electron microscopy. The surface of the chorion of the egg is granulated, and the micropyle occurs at the anterior end. The labrum of the first instar larva does not have sensilla, and the second to fourth instar larvae have setae on the head. The mature larva is characterized by the position and number of the integumental differentiations (sensilla and setae). On completion of larval development, an adecticous and exarate pupa is produced. As for the adult, the mandibles of the pupae are toothed. Five larval instars are recorded, based on statistical analyses of the sizes of the larval mandibles in combination with characters such as the number of exuviae and excretion of the meconium. Developmental time from egg to adult emergence was 18-20 days for males and 21-23 days for females at 21-26 degrees C, 55-85 relative humidity, and a 16L:8D photoperiod. The results show that the eggs and different larval instars of this parasitoid can be unambiguously identified only by scanning electron microscope.

The preimaginal stages and development of Spalangia cameroni Perkins (Hymenoptera: Pteromalidae) on Ceratitis capitata (Wiedemann) (Diptera: Tephritidae).

The development and morphology of the immature phases of Spalangia cameroni Perkins, 1910 (Hymenoptera, Pteromalidae) are described from a laboratory rearing culture maintained on Ceratitis capitata (Wiedemann, 1824) (Diptera, Tephritidae), using microscopic techniques, including light and scanning electron microscopy. The surface of the chorion of the egg is smooth and the micropyle occurs at the anterior end. The immature larvae are similar to the mature larva, differing mainly in the size of the head capsule and mandibles. The mature larva displays tubercules on the body segments as well as a pleurostoma and superior and inferior mandibular processes. On completion of its larval development, an adecticous and exarate pupa is produced. The mandibles of the pupa, as for the adult, are toothed. Three larval instars are recorded based on statistical analyses of the sizes of the larval mandibles and head capsules, in combination with such characters as the number of exuviae and excretion of the meconium. There are significant positive correlations between mandible length and width of larval head capsule with the number of instars, thus indicating that the mandible length and width of larval capsule are good predictors of the number of instars in this parasitoid. Developmental time from egg to adult emergence was approximately 33-34 days for females and approximately 28-29 days for males at 21-26 degrees C, 55-85 RH and a L16:D8 photoperiod. Our results show that the eggs and different instars of S. cameroni can be unambiguously identified only by SEM. Therefore, characterization of the immature stages of Spalangia species using SEM should be done before subsequent routine identifications using a binocular microscope or stereomicroscope.

Predatory habits of the grasshopper-hunting wasp Stizus continuus (Hymenoptera: Crabronidae): diet preference, predator–prey size relationships and foraging capacity

In a coastal salt-marsh of Spain, the digger wasp Stizus continuus primarily hunted for grasshoppers of the genus Heteracris, revealing (at least in the period of the study and in this area) this wasp to be almost monophagous. In contrast, grasshoppers of the genus Acrotylus were ignored by the wasps in spite of their high abundance in the environment. We hypothesize that this bias occurred because Acrotylus is found more often on the soil and on grasses, while Heteracris is nearly only found on Sarcocornia bushes, which probably represent the habitat mostly exploited by the wasps for hunting. The greater variance in size of the prey collected by larger females produced weak wasp–prey size correlations. Some wasps were observed to carry in flight prey weighing close to or more than the maximum theoretically possible, suggesting that they have to descend with prey to the nest from the above-soil hunting sites.

Offspring production and self-superparasitism in the solitary ectoparasitoid Spalangia cameroni (Hymenoptera: Pteromalidae) in relation to host abundance

Parasitoid fitness strongly depends on the availability and quality of hosts, which provide all resources required for larval development. Several factors, such as host size and previous parasitation, may affect host quality. Because self-superparasitism induces competition among a females offspring, it should only occur if there is an imperfect recognition of self-parasitized hosts or if there is a fitness advantage to self-superparasitism. Against this background, we investigated self-superparasitism and offspring production in Spalangia cameroni (Hymenoptera: Pteromalidae) in relation to the abundance of a novel host, Ceratitis capitata (Diptera: Tephritidae). Individual pairs of parasitoids were provided with either two (low host abundance) or ten (high host abundance) pupae per day. Under high host abundance, lifetime fecundity (number of eggs laid), offspring number, number of pupae parasitized and hosts killed were greater than under low host abundance, whereas the number of eggs per host was lower; and the proportion of hosts that did not produce offspring tended to be lower. The latter suggests the occurrence of ovicide, when hosts are scarce due to an at least imperfect recognition of previously self-parasitized hosts. Offspring production per parasitized pupa was higher when hosts were scarce and levels of self-superparasitism high, suggesting the existence of beneficial effects of self-superparasitism.

Diversity and Biogeographical Significance of Solitary Wasps (Chrysididae, Eumeninae, and Spheciformes) at the Arribes del Duero Natural Park, Spain: Their Importance for Insect Diversity Conservation in the Mediterranean Region

ABSTRACT Between 1997 and 2005, a study was made of the Chrysididae, Eumeninae, and Spheciformes wasps in the Arribes del Duero Natural Park (Provinces of Salamanca and Zamora, western Spain), a highly heterogeneous Mediterranean landscape. We collected, respectively, 127, 57, and 230 species of these groups, constituting ≈50% of the species known for the Iberian Peninsula. The inventory was fairly complete according to the final slope of the species accumulation curves. From a biogeographic point of view, the predominant elements of the Arribes del Duero fauna are Mediterranean in the broad sense, together with a high percentage of species of Euro-Atlantic distribution. The proportion of endemic species obtained is similar to those known for the whole of the Iberian Peninsula. The species endemic to the northern subplateau and to the southwestern quadrant predominate. The Arribes del Duero territory is the northern limit of the distribution of some Iberian-Maghrebine species, although it is also the southern limit of species widely distributed throughout central and northern Europe. The Atlantic influence in the territory has facilitated the persistence of some species, with an Atlantic or sub-Atlantic distribution, related in particular to riparian forests. This space constitutes a large eco-corridor that joins the north of the Peninsula to the south, linking communities corresponding to the Eurosiberian and Mediterranean biogeographic regions and to territories encompassed within the Temperate and Mediterranean macrobioclimates. Thus, because of its geographic situation and extensive latitudinal range, together with the fact that it has a good representation of European biodiversity, the Arribes del Duero Park is proposed as a priority area for insect diversity conservation in the Mediterranean region.

DESCRIPTIONS OF THE FINAL INSTAR OF EURYTOMA NODULARIS AND E. HERIADI (HYMENOPTERA: EURYTOMIDAE)

Abstract The final instars of Eurytoma nodularis and E. heriadi are described and illustrated. Morphological structures of diagnostic value are discussed. The most salient character shown by the mature larvae of these two species lies in the mandibles, which are simple (unidentate), a feature that, according to current knowledge, is only shared with E. verticillata.

Development, Preimaginal Phases and Adult Sensillar Equipment in Aganaspis Parasitoids ~Hymenoptera: Figitidae! of Fruit Flies

Aganaspis daci and Aganaspis pelleranoi (Hymenoptera: Figitidae) are important parasitoids of fruit flies. Here we studied, with light and scanning electron microscopy, aspects of their morphology that could help with plans to mass rear and thus contribute to improved pest control (preimaginal phases) and to shed light on parasitoid-pest relationships (sensillar equipment). The two species present a stalked egg, eucoiliform first and second-instar larvae and hymenopteriform third instar and mature larvae. The first instar presents tegumental differentiations in the mesoma and first metasomal segment in A. daci, but not in A. pelleranoi, while unlike other figitids, neither species displays setae in the mesosomal processes. Second and third instar and mature larvae present tegumental differentiations in A. daci, but not in A. pelleranoi. The moniliform (female) and filiform (male) antennae of A. daci and A. pelleranoi harbor seven types of sensilla, four of them (sensilla campaniformia, sensilla coeloconica type II, and two types of sensilla trichoidea) described here for the first time in Cynipoidea. The largest sensilla were the multiporous placoid sensilla, which were smaller and more numerous in A. pelleranoi. Species also differed to some extent in morphology of sensilla coeloconica. Observations on the ovipositor revealed the presence of coeloconic sensilla on Valva I in both species.

Trap-nesting Ancistrocerus sikhimensis (Hymenoptera: Eumenidae) IN NEPAL: nest structure and associates (Hymenoptera: Chrysididae; Acarina: Saproglyphidae)

Abstract The contents of 21 trap-nests located in Sagarmatha National Park, Nepal, in 2002 and 2003 revealed interesting aspects of the biology of Ancistrocerus sikhimensis Bingham (Hymenoptera: Eumenidae). The nests included 2-7 brood cells separated by mud partitions. The dimensions of these structures seem to increase from the first cell to the last one constructed by the wasp. Females always used all the available space of the trap-nests, and the variability in the number of cells per nest essentially depended on their different dimensions. All the emerged adults were females, and we suspect that this species is bivoltine, with a highly shifted sex ratio between the two generations. In 2002, the parasite Chrysis sp. aff. coelestina Klug, recorded for the first time on this host, was responsible for a rate of parasitism per nest of 0%-100%, with an average of 41.65%. A second cuckoo wasp, Chrysis violenta ultramonticola Linsenmaier, emerged from one nest in 2003. Most A. sikhimensis females housed, mainly on the abdomen, hypopi of the mite Vespacarus sp., which is known to be involved in other wasp-mite associations. Unlike other mite-symbiotic eumenid wasps, A. sikhimensis does not present an acarinarium on its body to house the mites.

Temporal asynchrony and spatial co-occurrence with the host: the foraging patterns of Nemka viduata, a parasitoid of digger wasps (Hymenoptera: Mutillidae and Crabronidae).

Studies which quantitatively analyse how aculeate parasitoids exploit their window of opportunity to find and attack a host are scarce, despite the recognized importance of parasitic pressure as a driving force that promotes aggregate nesting in their hosts. We have studied the activity and behaviour of the velvet ant Nemka viduata, an ectoparasitoid of immature stages of the digger wasp Stizus continuus. Due to the resource exploited by the parasitoid (mature larvae and prepupae), and in general agreement with basic optimal foraging theory, we expected a major activity at late stages of the host seasonal provisioning period, an independence from the host daily provisioning patterns and a spatial positive association with host nest density. In accordance with these predictions, during the season, the parasitoid resulted was more active at the end of the host provisioning period, and across the day, it showed an inverse quadratic pattern of activity, in contrast to the positive one shown by the host. Thus, at both temporal scales, N. viduata activity was highly asynchronous with that of the host. At a spatial scale, however, the activity of the velvet ants was correlated with host nest density, although there is weak evidence suggesting that areas of high host density suffered from a higher rate of parasitism. Multivariate analyses confirmed a number of relevant factors associated with velvet ants’ activity, including nest density (positive), air temperature and the hour of the day (both negative). In addition, the activity of both male S. continuus and male N. viduata entered in the models in association with female parasitoid’s activity, probably because of their mating strategy.