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Mesocheira bicolor (Fabricius) is a cleptoparasite bee, widely distributed in the New World from Mexico to northern Argentina. In Argentina, this species is only documented from Formosa. In this contribution, we report new records of males and females reared from trap nests obtained from different studies about nesting biology of solitary bees in pre-existing cavities in several Argentinian provinces. Also, we studied material from Argentinean research collections, and we searched for occurrence data in the Global Biodiversity Information Facility. Adults of M. bicolor were reared from nests of Centris (Hemisiella) tarsata and C. (Hemisiella) nigriventris Burmeister. Here, we reported eight new provincial records that widely increase the geographical distribution of this species in Argentina, expanding its austral-most distribution record by more than 1,000 km. [ABSTRACT FROM AUTHOR]

Pronomopsis rubripes Hermann, and Pronomopsis talabrensis Artigas are reported for the first time from Argentina (Salta and Jujuy) and the male terminalia of P. chalybea Hermann and P. talabrensis are described and illustrated for the first time. An updated distribution map and a key of the species of Pronomopsis Hermann are also provided. [ABSTRACT FROM AUTHOR]

Two species of syrphid flies are reported for the first time in Argentina: the neotropical Rhingia nigra Macquart and exotic Eumerus obliquus (Fabricius). Individuals of both species were captured in the province of Misiones. Moreover, another individual of E. obliquus was reared from a decaying stem of Austrocylindropuntia subulata (Cactaceae) in the province of Tucumán. Finally, we report the presence of Eumerus strigatus (Fallén) in the province of Chubut, more than 400 km to southwest from its southernmost record. [ABSTRACT FROM AUTHOR]

The bee fly Toxophora aurea Macquart is reported for the first time in Argentina. One single specimen of this species was reared from a nest of Isodontia costipennis (Spinola) (Hymenoptera: Sphecidae) in the province of Formosa and others were captured in southern Misiones province, and others housed in entomological collections from the provinces Chaco, Santiago del Estero and Santa Fe. Data about the biology of Toxophora leucon Séguy from individuals reared in nests of Cyphomenes anisitsii (Brèthes), Pachodyneurs guadulpensis (Saussure) and Zethus dicomboda (Spinola) (Hymenoptera: Vespidae: Eumeninae) in the province of Formosa are also reported. These are the first data about the reproductive ecology of these parasitic flies in Argentina. [ABSTRACT FROM AUTHOR]

This contribution deals with the most common and frequently collected species of Megachile (Dactylomegachile) in Argentina. The taxonomy of seven species is clarified, presenting sex associations for all but one of the species, M. binota, the male sex of which remains unknown. In most cases sex associations are based on specimens reared from trapnests. The following new synonymies are proposed: M. nigella Vachal is a junior synonym of M. ctenophora Holmberg; M. parsonsiae Schrottky and M. riojanensis Mitchell are junior synonyms of M. infima Vachal; M. trochantina Vachal and M. perspicua Mitchell are junior synonyms of M. leucografa Friese; M. albopunctata Jörgensen is a junior synonym of M. tetrazona Friese; M. suspecta Vachal and M. impudens Mitchell are junior synonyms of M. vagata Vachal. Redescriptions, distributional data, and a key to the studied species are given. [ABSTRACT FROM AUTHOR]

The exotic syrphid Eumerus strigatus (Fallén) is reported for the first time in Argentina. Individuals of this species were captured in two sites distant more than 1,000 km (Villalonga, province of Buenos Aires, and Pocito, province of San Juan) associated with onion crops (Allium cepa L.). We propose the monitoring of this phytophagous hover fly because of its potential risk for this important horticultural crop. [ABSTRACT FROM AUTHOR]

Sunflower (Helianthus annuus L.) is an important oilseed crop in Argentina. During three agricultural years, the diversity and abundance of diurnal floral visitors of sunflower heads were determined in eight sites spanning much of this crop's cultivation area in Argentina. Seventy-six morpho-species of floral visitors, belonging to eight orders, were captured on sunflower. The principal order was Hymenoptera, with 37 species or morpho-species, of which 32 were bees (Apoidea). The most represented bee families were Apidae (13), Megachilidae (11) and Halictidae (7). The domestic bee (Apis mellifera I.) accounted for 93% of the visits. Floral visitor composition did not show an identifiable variation pattern either throughout the day or with respect to the distance to the edge of the crop, but varied among sites. It is concluded that the domestic bee is the main sunflower pollinator in Argentina, although several native bee species (Melissodes tintinnans (Holmberg), M. rufithorax Brèthes, Melissoptila tandilensis Holmberg, and Megachilespp.) could be considered as potential crop pollinators. [ABSTRACT FROM AUTHOR]

Sunflower (Helianthus annuus) is an oilseed crop pollinated by Apis mellifera L. and other diurnal bees in different regions of the world. However, their flowers are also visited by insects active at night. During three agricultural years, the diversity of nocturnal visitors to sunflower heads was assessed in five different sites in Argentina. The foraging behavior of the main visitors as well as the stigmatic receptivity variations along the day were also studied in order to determine whether or not these visitors contribute to pollination. At least 67 species or morpho-species belonging to four nocturnal visitor orders were recorded. The richest and most abundant order was Lepidoptera (44 species or morpho-species, five families), followed by Coleóptera (18 species or morpho-species, nine families), Orthoptera (three morpho-species, one family) and Blattaria (two species, one family). Lepidopterans foraged exclusively for nectar while species in other orders consumed pollen and/or floral parts. However, stigma receptivity was greater during the day, peaking at midday (12:00 - 14:00). Unexpectedly, moth species widely outnumbered bee species as sunflower visitors. Since moths potentially transfer pollen at a time of the day when stigmas are least receptive, it is unlikely that they do effectively pollinate sunflowers. [ABSTRACT FROM AUTHOR]

There is a growing consensus that the world is facing a pollination crisis. To mitigate crop pollination deficits, some management strategies include the massive introduction of managed bee species, yet quite often they are applied blindly, as information on crop pollination effectiveness for each single pollinator species of assemblages is usually not available. Therefore, the introduction on managed species is not always the best option to improve crop yields. Here, by using the highly pollinator-dependent alfalfa crop (Medicago sativa L.) as a case study, we propose the use of the effectiveness landscape framework to identify key crop pollinator species. According to this framework, in a mutualistic interaction, each species´ effectiveness is represented by the product of a quantitative component and a qualitative one, these being measures of the outcomes of this interaction. We applied this framework for two managed and four wild bee species that visit alfalfa in fields southwest of Buenos Aires province, Argentina. We dissected the quantity components of the pollinator effectiveness landscape by estimating two quantitative subcomponents: visitation rate and flower tripping rate. Also, we estimate pod set as a qualitative component without dissecting it in subcomponents. Our results showed that the contribution of both components and the resulting pollinator effectiveness varied among pollinator species, indicating a contrasting effectiveness of different bee species on alfalfa pollination. For example, pollinator effectiveness was higher for managed than for wild bees, as consequence of their very high visitation rate, however, wild bee flower tripping rate and pod set were as high as managed ones. In fact, wild bees were more effective in promoting flower tripping than one of the managed bees (A. mellifera). This approach allowed us to assess which effectiveness components and subcomponents make pollinator species more or less effective, thus providing valuable information to identify key species to be enhanced to help in closing yield gaps. We suggest that the application of the effectiveness landscape framework would be useful to develop strategies to improve crop pollination service in pollinator-dependent crop systems. • Identification of key crop pollinator species is essential. • Effectiveness landscape decomposes effectiveness into components and subcomponents. • Effectiveness landscape allows us to assess the effectiveness of each crop pollinator species. • This approach is useful for crop pollination management strategies. [ABSTRACT FROM AUTHOR]

Temporal changes of flesh flies abundance were simultaneously recorded at monthly intervals during a year in a woodland and in a grassland at the "Reserva Ecológica Costanera Sur" (RECS), Buenos Aires city, Argentina. Samples were taken at monthly intervals (February 2004-January 2005). Hourly captures of adult flies (10:00 am - 04:00 pm) were taken each sampling date with a hand net. Temperature was recorded at each hourly capture. The baits used were 200 g of rotten cow liver and 200 g of fresh dog faeces. Records of abundance included only species whose abundance was ≥30 individuals accumulated during the whole sampling period. Considering overall abundance, a non-parametric Chi-square test was used to estimate deviations of an expected habitat and bait preference ratios of 1:1. The same criterion was applied to include species in a contingency table to describe their seasonality. The final matrix included four species whose associations to seasons were analyzed by using a Correspondence Analysis. To normalize the data, a log 10(n+1) transformation was applied prior to the analysis of correlation. Pearson product-moment correlations were used to examine the relationship between flesh-fly abundance with temperature and habitat preference. The entire sample accumulated 1 305 individuals and 18 species. The flies were more abundant in the grassland than in the woodland. Microcerella muehni, Oxysarcodexia paulistanensis, O. varia and Tricharaea (Sarcophagula) occidua exhibited the higher relative abundance, representing the remaining species less than 8 % of the entire sample. Most of the recorded species showed preference for faces as bait. Concerning the dominant species, all of them but M. muehni, a suggestively termophobic species, prevailed in late spring-summer. The observed species arrangement at both sites indicates low species diversity and equitability and high information per individual in the average. The referred community traits would indicate the possible effects of environmental disturbance due to the proximity of study sites to dense urban settlements. [ABSTRACT FROM AUTHOR]

Biotic pollination is an essential ecosystem service for agricultural production and is reflected in the high number of crops that depend on insect pollination in order to produce profitable yields. Alfalfa (Medicago sativa) is a crop whose flowers need to be visited by a bee to be pollinated for seed production, making it highly pollinator-dependent. Two managed bee species are currently used to pollinate this crop: the alfalfa leafcutting bee (ALCB), one of the most efficient alfalfa pollinators, and the honey bee (HB), whose efficiencies could be highly variable among production sites. Besides, there are many other wild bee species (WBs) that are effective pollinators of alfalfa, but little attention has been placed on them, especially in Argentina, where alfalfa seed production is deficient. Here, we evaluate the contribution of both managed species and WBs on alfalfa pollination services in one of the most important alfalfa seed productive regions of Argentina. During the span of two years, we calculated pollen limitation in different pollinator managed scenarios: with and without ALCBs (ALCB+ and ALCB−, respectively), and we also evaluated the relationship between pollen limitation and all bee species visitation rates. Our results show that the ALCB is a very effective pollinator of alfalfa, since ALCB+ lots have less pollen limitation (32%) compared to ALCB− lots. In contrast, HBs seem to have a detrimental effect in pollination service in ALCB+ lots and a positive effect in ALCB− lots. This differential effect could be due to differences in foraging behavior caused by competition between HBs and ALCBs. Finally, in spite of their low abundances, we found that an increase in WB visitation rates substantially reduces pollen limitation. In spite of ALCBs being a good alfalfa pollinators, the difficulty and cost of managing them hinder its widespread use. The use of WBs seems to be a good alternative, and practices that improve their abundance and diversity should be implemented to improve alfalfa pollination service. • Alfalfa reproduction highly depends on cross pollination by a bee. • Alfalfa leafcutting bee management improve alfalfa pollination service. • Honey bee differs in its efficiency between alfalfa crops. • Increased wild bee abundance enhances pollination service of alfalfa crops. [ABSTRACT FROM AUTHOR]

Bee flies of the genus Heterostylum Macquart are medium-sized species (1015 mm) characterized primarily by a robust body covered with long pile and by an indented hind margin of the eye (Cunha et al. 2007). There are several studies on the immatures of some species of Heterostylum (Bohart et al. 1960; Yeates Greathead 1997), which are considered ectoparasites of fossorial solitary bee larvae and pupae (Yeates Greathead 1997).

We conducted a whole year research on the ecology of Mansonia indubitans and Ma. titillans in Macáes Pond, Costanera Sur Reserve, Buenos Aires, Argentina. The usage of different floating plants by immature instars and their overwintering was analyzed. The percentage of usage of the available floating macrophytes (Pistia, Limnobium, and Salvinia) by the larvae and pupae was studied. Also, we defined positivity (P+) as the percentage of plants with immature instars for each plant genus on a monthly basis. Ma. immature instars were captured throughout the year and Pistia was the resource most commonly exploited by the mosquitoes. The percentage of fourth-instar larvae and pupae on Pistia roots with respect to total immature instars captured was assessed on a monthly and seasonal basis. The proportion of fourth-instar larvae and pupae from both species of Mansonia on water lettuce roots, showed significant differences between months and seasons. Our results suggest that the populations of Ma. indubitans and Ma. titillans in Macáes Pond, survive during winter mainly as fourth-instar larvae.

Larvae and pupae of the genus Mansonia Blanchard attach to the roots of aquatic plants by means of modified structures to obtain oxygen. A study of the association of larval Ma. indubitans and Ma. titillans with floating macrophytes was conducted at Macies Pond, Argentina. Fifty-four sampling units were taken from January to May 2003. Three genera of host plants were considered: Pistia, Limnobium, and Salvinia. A total of 402 immatures of Ma. indubitans and 217 of Ma. titillans were captured and associations between Mansonia immatures and roots of each genera were assesed. Significant association was noted between Ma. indubitans and certain host plant species (K-W H=42.74, df=2, p<0.001). The same result was observed for Ma. titillans (K-W H=23.42, df=2, p<0.001). Both Mansonia species utilized roots of P. stratiotes in significantly higher proportions than expected by random selection. Both species showed significant negative association with Salvinia spp., while no clear relationships were detected with L. laevigatum.