S. F. Gayubo

Conservation of European environments: The Spheciformes wasps as biodiversity indicators (Hymenoptera: Apoidea: Ampulicidae, Sphecidae and Crabronidae)

The aim of this work is to propose the use of the Spheciformes wasps (Hymenoptera: Apoidea: Ampulicidae, Sphecidae and Crabronidae) as indicators of European biodiversity. One advantage of studying this group of insects lies in the regulating effects that such wasps have on other insect populations. We discuss the applicability of seven criteria, taken from the literature, to use the Spheciformes wasps as an indicator group, with respect to which parameters this group offers guarantees of being good indicators of biodiversity, both for predicting the diversity of other groups of animals and for all the species of a given area.

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.

Using higher taxa as surrogates of species-level data in three Portuguese protected areas: a case study on Spheciformes (Hymenoptera)

Protected areas are the focus of most conservation efforts worldwide. Despite vast amount of investment in protected areas, biodiversity loss continues. This has led to increasing efforts to develop measures to assess the effectiveness of protected areas. The reliability of these measures depends on the quality of the information collected. However, because the resources available for the collection of information are limited, several strategies have been developed to reduce the resources necessary. In this study the combination of two resource reduction approaches—bioindicator and higher-taxa—is proposed. Spheciformes have been found to be useful as biodiversity, ecological and environmental indicators. Identification to the species level is usually very costly, but the use of genus-level information has been suggested. Tribe- and genus-level data for Spheciformes were assessed for their ability to predict the number of species independently of other variables—sampling area, geographic location, vegetation type, disturbance regime, and sampling effort—at three Portuguese protected areas. Tribe and genus-level data were found to be good indicators, with genus being the more reliable taxonomic level. Sampling effort was the only external variable that affected the relationship between species and higher-taxa richness. Genus-level data were also found to be useful for ranking sites according to richness or composition, and for determining richness-based and rarity-based complementary sets of sites for conservation. Using genus richness as a surrogate for species richness seems a promising approach for monitoring and contributing to the establishment of protected areas in Portugal and the entire Mediterranean region.

Territorial dynamics and contest behaviour in the solitary wasp Stizus continuus (Hymenoptera: Apoidea: Crabronidae)

Territorial and agonistic behaviour in male sand wasps (Stizus continuus) was investigated in order to determine the influence of body size on territory maintenance and the strategies used to reduce the costs associated with territoriality. Size is the decisive factor in the capacity of males to defend a territory against other competitors: (1) in the disputes observed, the largest male was usually the winner; (2) territorial males were larger than those never seen occupying territories; (3) the size of males occupying territories that were left vacant when their inhabitants were removed experimentally was smaller. To optimize their territorial behaviour, males only defend sites in the nesting area and only when virgin females are emerging (from 0700 to 1300), and reduce the time spent perching (as opposed to patrolling) as temperature increases during the morning. To reduce costs associated with contests, males fight only with rivals of similar size and show a greater tendency to fight with larger males when virgin females are most likely to emerge (from 0800 to 1000). This suggests that males may be able to estimate the size of rivals immediately before an attack (face-to-face hovering), and leave when the opponent is significantly larger.

Description of the Mature Larvae of Chrysis gracillima and Omalus biaccinctus and New Data on the Biology of Trichrysis cyanea (Hymenoptera: Chrysididae)

The mature larvae of Chrysis gracillima Forster, 1853 and Omalus biaccinctus (Buysson, 1893) are described and compared with others known in the tribes Chrysidini and Elampini, respectively. Additionally, new data are reported on the biology of Trichrysis cyanea (L., 1758).

Are solitary progressive-provisioning wasps optimal foragers? A study with the digger wasp Bembix merceti (Hymenoptera: Crabronidae)

Summary Bembix merceti, a central-place forager that captures dipterans to feed its larvae, could be considered a suboptimal forager. The females tend to optimize their provisioning flights, capturing prey in proportions different from those present in the surrounding environment. These wasps make a positive selection of families of flies with greater mean weights even though they are less abundant and, within the families whose weight is not too great, capture individuals whose weight is larger than the mean. Selection is based on prey size and not on the type (family) to which the prey belongs. A significant correlation between the weight of each female and the weight of the largest prey captured by the wasp was found, suggesting that the females capture prey in consonance with their lift capacity. Nevertheless, captures were not optimized maximally; the females maintained a margin with respect to the maximum prey weights that they could transport efficiently. This margin could be related to the low availability of large prey in the environment; to the type of progressive provisioning shown by the females of this species; and to other factors, such as the good manoeuvrability of their prey and the pressure from their natural enemies and congeners.

Description of the mature larva of the sand wasp Bembix bidentata and its parasitoids (Hymenoptera: Crabronidae, Chrysididae, Mutillidae).

ABSTRACT The mature larvae of Bembix bidentata and one of its chrysidid and mutillid parasitoids are described and illustrated, and structures of phylogenetic value are discussed. The mature larva of B. bidentata is characterized by an integument with short setae (< 40 µm) and scanty microspinules. The ratio between the length of the antennal papilla and the width of the antennal orbit is a character state that can be used in the separation of the final instar of European Bembix species. The mature larva of Chrysidea disclusa is characterized by a combination of two character states: (1) an atrium without asperities or weak lines on the circumference, and (2) antennal papillae longer than broad; the larval morphology of Chrysidea previously was unknown. The mature larva of Chrysura hybrida is characterized, within the genus Chrysura, by the autapomorphy “maxillary palpus with 4 sensilla at apex.” The range of hosts of Chrysura spp. is broadened to the Crabronidae. The mature larva of Smicromyrme rufipes is characterized, within the Mutillinae, by having more than 8 apical setae and no apical papillae on the labium.

The Significance of the Vestibular Cell in Trap Nesting Wasps (Hymenoptera: Crabronidae): Does its Presence Reduce Mortality?

In a study carried out with the trap-nesting solitary wasp Trypoxylon attenuatum (Hymenoptera: Crabronidae) in 2000, we analysed the significance of different nest characteristics, like the vestibular cell and empty intercalary cells, and its role in the reduction of mortality. Analysis of the presence of the vestibular cell suggested that it represents a nest completion structure, whose presence reduces mortality in the initial stages (M1) but does not affect that due to chrysidid parasitoids (MP). The length of such vestibular cell was found to depend mainly on the space between the last provisioned cell and the exterior, pointing to a possible role in the reduction of the remaining space that could be used by other females to establish a nest exterior to the completed one. The empty intercalary cells were smaller than the vestibular cells, did not affect M1 or MP mortality rates in the nest, and exhibited an “aggregated” pattern of occurrence. This suggests that they could be the result of “abnormal” behaviour by the female owning the nest. The total mortality rate decreased with the increase in the number of cells in the nests, also being greater in nests established at low heights above the ground. M1 was lower in the innermost cells, while MP increased towards the interior and in the nests with more cells. The distribution in the nests of cells parasitized by Trichrysis cyanea (the main natural enemy found in the wasp population studied) reflects an “aggregated” pattern, suggesting repeated attacks against certain nests.

ECOLOGY OF CRABRONID WASPS FOUND IN TRAP NESTS FROM SPAIN (HYMENOPTERA: SPHECIFORMES)

Abstract We report data obtained concerning the occupation of trap nests by xylicolous Crabronidae (sensu Melo 1999) in a study carried out in central Spain between 1992 and 1995. In particular, we analyze the data on the occupation of the nests for Psenulus concolor (Dahlbom), Trypoxylon attenuatum F. Smith, and Trypoxylon beaumonti Antropov. All three species use pre-existing cavities of 2-4 mm to establish their nests. The mortality rates varied between 33% and 55%, and of special interest was the variation between the two species of Trypoxylon L. and the absence of mortality due to natural enemies in P. concolor. In the three species, mortality was similar along the nests, with no increase in the innermost or outermost cells. Trichrysis cyanea (L.) was the most abundant natural enemy in the nests analyzed. Sex distribution was not random in any of the species studied: in P. concolor and T. attenuatum, the males developed in the outermost cells, while in T. beaumonti they appeared in the innermost ones. The sex ratio did not deviate from 0.5 in P. concolor and T. attenuaum, although in T. beaumonti, the number of females was significantly higher than that of males.