Abstract

All the members of Eucharitidae are parasitoid of ants. Argentina has 14 genera and 41 species, but little is known about their biology. Herein are provided new data for host associations (host ant and/or host plant) of Galearia latreillei, Kapala spp., Latina rugosa, Orasema aenea, and Orasema sp. A revision of the most relevant biological aspects of Dicoelothorax platycerus, Latina rugosa, Neolirata alta, N. daguerrei, Lophyrocera variabilis, Orasema argentina, O. salebrosa, O. simplex, O. susanae, O. worcesteri, and O. xanthopus is included. New records of K. sulcifacies, Lo. plagiata, and Ob. semifumipennis in Argentina are presented. Galearia proseni is synonymized with G. latreillei.

1. Introduction

Eucharitidae parasitize the immature stages of Formicidae and are among the most diverse hymenopteran parasitoids of eusocial insects [18]. Females are oviparous and pro-ovigenic and lay their eggs inside or on plant tissues, either individually or in masses. They oviposit away from the host, with the active first instar larva (planidium) responsible for getting into the ant nest through various associations with foraging adult ants [9]. Once in contact with the larval ant host, the planidium either remains as an external parasite or burrows into the host. Upon pupation of the host, the larva migrates to the ventral region of the thorax, just posterior to the legs of the newly formed pupa, then resumes development through two additional instars [10, 11]. The adults emerge and leave the nest on their own or may be carried by the ants and deposited in the accumulation of colony waste [10, 12, 13].

Eucharitidae are present in all zoogeographic regions but most abundant in the tropics [8]. Fifty-four genera and about 420 species worldwide have been described. In Argentina, 14 genera and 41 species have been reported [8, 1416].

Eucharitidae were well studied in a series of early taxonomic papers by Gemignani [1719]; however, very little information was provided on their biology. This paper reviews our current understanding and contributes new data for some of the Argentinean species.

2. Materials and Methods

Females were collected by sweep netting and provided twigs with leaves, fruits, and flowers of different species of plants in 10 × 3.5 cm plastic tubes to monitor oviposition habits. Host plants with eggs extracted from the field or oviposited by the captive females were placed into a cylindrical glass container of 10 × 10 cm with dampened cotton until emergence of the first instar (planidium).

Ant nests with adults, brood, and debris were collected into plastic containers. Adults and immature stages were then sorted from the debris, examined for parasitism, and in some cases returned to the containers to allow further development of immature ones. The immature stages were examined once daily until all parasitoids or ants emerged from the cocoons. In the cases where both parasitoid sexes emerged, they were put together in a cylindrical glass container of 10 × 10 cm containing different types of plants to allow for oviposition after mating.

A Leica MZ12 stereomicroscope was used for observations. Images were obtained using GT-Vision Ento-Vision software operating on a Leica M16 zoom lens linked to a JVC KY-F75U 3-CCD digital video camera or Leica Application Suite (version 3.5.0) software operating on a Leica MZ12 linked to a Leica DFC295 digital video camera. Images were enhanced with Corel Photopaint and Corel Draw (version 15). Some images were processed using Deep Focus (Stuart Ball).

The biogeographical distribution and classification of ecoregions in Argentina was taken from Morrone [20] and Bertonatti and Corcuera [21]. Geographic coordinates for eucharitid localities were estimated using Google Earth (version 6.2.2.6613).

3. Genera and Species of Eucharitidae from Argentina

Two of the four subfamilies of Eucharitidae are represented in Argentina, Oraseminae and Eucharitinae (Table 1). Oraseminae is represented only by Orasema Cameron. The Eucharitinae are comprised of 12 genera of Eucharitini with a dubious record of Psilocharis Heraty (Psilocharitini) from Déan Funes (Córdoba) [5].

3.1. Dicoelothorax Ashmead

This genus includes two species distributed in the Neotropical region: D. parviceps Cameron (Argentina, Brazil, Colombia, and Guyana) and D. platycerus Ashmead (Argentina, Bolivia, and Brazil) (Figures 1(a) and 1(b)) [8, 14, 22]. Biological information is only available for D. platycerus [22].

3.1.1. Dicoelothorax platycerus Ashmead

Habitat and location are as follows. Specimens were collected in San Vicente (Tucumán). The vegetation of this region is characterized by dry forests, dominated by deciduous, spiny, and small-leaves plants typical of the Chaco ecoregion [40] (Figures 1(c) and 1(d)). The host plant, Pseudabutilon virgatum (Cav.) (Malvaceae), is a ligneous shrub that occurs throughout the area and persists year round.

Life history and host ants are next. A single gravid female oviposited about 40 eggs per 1 mm2 on the underside of leaves (Figure 1(e)), and eggs hatched within 10 days. First instars (planidia) (Figure 1(f)) are mobile and have a propensity to jump; larvae presumably attach phoretically to foraging ants under the host plant and get carried back to the ant nest where they attack the ant larvae [3]. Of two pupae of D. platycerus obtained from the host ants nest one male emerged 12 days after the nest was excavated, whereas the other pupa (female) did not emerge (Figure 2(d)).

Ectatomma brunneum F. Smith (Ectatomminae) workers were observed and sampled from under the plants with Dicoelothorax. Of three ant nests found, immature ones were in two of them (H1 and H2). The disposition of chambers and general structure of nests are similar to those observed by Lapola et al. [41] (Figures 1(g) and 2(a)). Nest H1 contained 17 cocoons and 2 ant larvae, and nest H2 had 97 ant larvae and no cocoons. The percentage of parasitism ranged from 6.2% in H2 to 21% in H1. Of the 17 cocoons (H1) recovered, there were two cocoons each with one pupae of D. platycerus (1 female and 1 male) and 2 ant prepupae parasitized by second instars of D. platycerus (Figure 2(b)). In nest H2, 6 of the larvae were parasitized by externally located planidia (Figure 2(c)).

3.2. Galearia Brullé

The genus is comprised of two species, G. latreillei (Guérin-Méneville) and G. proseni Gemignani. Heraty [8] argued that the Argentinean male described as G. proseni by Gemignani [19] was likely the male of G. latreillei (Figures 2(e) and 2(f)). Based on the morphological similarity of a reared male with G. proseni (=Pseudokapala proseni), and its subsequent mating with a female of G. latreillei, infer that the suggestion by Heraty is correct and propose here a new synonymy of G. proseni with G. latreillei. The one species has a widespread Neotropical distribution, being present in Argentina, Bolivia, Brazil, and Venezuela [8, 14].

The only known biological record was from Gemignani [17] in which he mentioned that an adult of G. latreillei (=Thoracantha latreillei) was collected from the waste pile of a nest of Pogonomyrmex cunicularius Mayr (=P. carnivora), but this ant association is likely invalid [8].

Galearia latreillei was collected in northcentral and northwestern Argentina, and information on life history, immature stages, and host association is included.

3.2.1. Galearia latreillei (Guérin-Méneville)

Habitat and locations are as follows. Specimens were collected in Cabeza de Buey (Salta), Campo Gallo, Suncho Corral, and Tintina (Santiago del Estero). The Cabeza de Buey locality consists of mixed yunga (humid mountain forest) and xeric lowland Chaco vegetation. In the two localities in Santiago del Estero, located in the center and north of the province, the vegetation is typical of the chaco ecoregion (Figure 3(a)). The host plant, Sida cordifolia L. (Malvaceae), is a perennial, herbaceous plant with stems that are yellow-green, hairy, long, and slender, and their leaves are oblong-ovate, covered with hairs (Figure 3(b)).

Life history and host ants are next. Both sexes of G. latreillei were obtained from a nest of Ectatomma brunneum. The adult wasps were together for two days before mating occurred. The female then oviposited about 400 eggs that were dispersed among the spicules forming the pubescence on the stem of S. cordifolia near to the leaves or in the underside of leaves near the base (Figure 3(c)). Eggs hatched within 11 days. The planidia were very mobile and had a propensity to jump.

Nests of Ectatomma brunneum were excavated from near to the host plant, with immature ones found at a depth of 6 to 8 cm. From 50 cocoons, we extracted 10 pupae of G. latreillei. One male and one female emerged about 4 days after the nest was excavated, whereas the other pupae did not emerge (Figure 3(f)). Three other cocoons yielded one second-instar and two third-instars (Figures 3(d) and 3(e)). Of the 50 cocoons recovered, 13 were attacked giving a percentage parasitism of 26%.

Discussion. Ectatomma brunneum has also been reported as the ant host for Dicoelothorax platycerus [22] and for an unidentified species of Kapala Cameron (Eucharitidae: Eucharitini) in French Guiana [42]. Similarly, another species of the same ant genus, E. tuberculatum (Olivier), is known to be attacked by three different eucharitid genera, Dilocantha Shipp, Isomerala Shipp, and Kapala [43].

3.3. Kapala Cameron

Kapala includes 16 species, but there are many undescribed species in the Neotropical region. It is widespread and diverse in both the Nearctic and Neotropical regions and also includes one widespread afrotropical species, Kapala ivorensis Risbec [8].

In Argentina, 5 species were recorded: K. argentina Gemignani, K. chacoensis Gemignani, K. furcata (Fabricius), K. splendens Ashmead, and K. sulcifacies (Cameron) [8, 14]. Partial biological information is available for K. furcata and K. sulcifacies (summarized later). New data is also added for two unidentified species.

3.3.1. Kapala furcata (Fabricius)

This species was observed ovipositing on floral buds of Mikania sp. (Asteraceae) [2] that were infested with aphids [3].

3.3.2. Kapala sulcifacies (Cameron)

This species has been reported as ovipositing in floral buds of Cordia curassavica (Jacq.) Roem. & Schult. (Boraginaceae) (=Cordia macrostachya), Gossypium hirsutum L. (Malvaceae), and in a flowering asclepiad [23], with eggs laid in clusters of 200–300 eggs [24].

3.3.3. Kapala spp.

A species sampled in Campo Gallo (Santiago del Estero) oviposited into flower buds of Sphaeralcea bonariensis (Cav.) Griseb. (Malvaceae), with the planidia emerging 9 days after oviposition. Another species was collected in Rosario de la Frontera (Salta) over an unidentified Sapindaceae, but no oviposition was observed.

3.4. Latina Koçak and Kemal

Latina (=Laurella Heraty) includes four species distributed in the Neotropical region: Latina bonariensis (Gemignani) (Argentina), L. guriana (Heraty) (Venezuela), L. rugosa (Torréns, Heraty and Fidalgo) (Argentina) (Figures 4(a) and 4(b)), and L. vianai (Gemignani) (Argentina) [8, 25].

Latina rugosa was collected in northwestern Argentina and the taxonomic and biological aspects provided by Torréns, Heraty, and Fidalgo [25].

3.4.1. Latina rugosa (Torréns, Heraty, and Fidalgo)

Habitat and location are as follows. Specimens were collected at Rosario de la Frontera (Salta); the collection site was a forest of Piptadenia macrocarpa Benth. (Cebil Colorado) (Fabaceae). The vegetation of this region corresponds to the Yungas and Chaco ecoregions [40]. The host plants, Serjania glabrata (Sapindaceae), are perennial shrubs with pubescent and serrated leaves, with the plants dispersed between trees in the collection area (Figures 4(c) and 4(d)).

Life history and host ants are next. Adults of L. rugosa were collected in the same location, mainly close to or on the host plant. A single gravid female oviposited about 25 eggs per 1 mm2 on the underside of leaves (Figure 4(d)). Eggs hatched within 6 days. The planidia (Figure 4(e)) were mobile and able to jump.

Odontomachus chelifer (Latreille) (Ponerinae) workers were observed and collected under the host plants from which L. rugosa were collected. One O. chelifer nest was identified only by a small ground opening. The ant nests were excavated and the cocoons and ants larvae extracted at a depth of 16 cm; however, the nest appeared to be much deeper, and it was difficult to tell whether the entire brood was extracted. Of the five ant larvae extracted, one had three planidia externally attached (Figure 4(f)), while of the 19 cocoons only one planidium was found attached externally to a prepupa. From this sample, the percentage of parasitism was 8.3% of 24 immature ones.

Discussion. Data presented here confirm the ant host association of Latina rugosa as Odontomachus chelifer. This ant genus is also the host of other eucharitids genera as Ancylotropus Cameron, Chalcura Kirby, Schizaspidia Westwood, and Kapala Cameron [8, 42].

3.5. Lophyrocera Cameron

Lophyrocera Cameron includes seven species distributed across South and Central America and the western United States (Neotropical and Nearctic): L. apicalis Ashmead (USA), L. daguerrei (Gemignani) (Argentina), L. chilensis (Brèthes) (Chile), L. plagiata (Walker) (Argentina and Brazil), L. pretendens (Walker) (Brazil), L. stramineipes Cameron (Panama), and L. variabilis Torréns et al. (Argentina) (Figures 5(a)–5(c)) [8, 14, 26].

Lophyrocera variabilis was collected in northwestern Argentina, with information available on life history, immature stages, and host association [26].

3.5.1. Lophyrocera variabilis Torréns, Heraty, and Fidalgo

Habitat and location are as follows. The habitat consists of mixed Yungas and Chaco vegetation in Los Chorrillos (Tucumán) (Figure 5(d)). The host plant, Vassobia breviflora (Sendtn) Hunz. (Solanaceae), common name “Chalchal de la gallina”, is a spiny shrub with globe-shaped fruits, which are red in color when mature (Figure 5(e)) [44].

Life history and host ants are next. Females were observed ovipositing in the immature (green) fruit of V. breviflora, with eggs deposited in small masses within the fruit (Figure 5(f)). Only undeveloped eggs were obtained from immature fruits while mature fruits taken from the ground had mature eggs and larvae. The planidia (Figure 5(g)) crawl and do not have the ability to jump.

In the field, a species of Camponotus Mayr (Formicinae: Camponotini) visited and foraged below the host plant. Camponotus are known to collect fruit pulp and small seeds [45], and a direct interaction of foragers with the ripe fruit and planidia is very likely, as proposed for Pseudochalcura [9].

Nests of Camponotus were located under host plants or within a few meters (Figure 6(a)). In total, 35 Lophyrocera pupae were found in 7 of the 13 nests excavated, and of these, three had two pupae of L. variabilis in the same cocoon (Figure 6(b)). No larvae were found. The parasitism rate ranged from 0 to 6.21%.

3.6. Neolirata Torréns and Heraty

This genus includes three species distributed in the Neotropical region: N. alta (Walker) (Argentina, Brazil, and Uruguay) (Figure 6(c)), N. daguerrei (Gemignani) (Argentina, and Brazil) (Figures 7(a) and 7(b)), and N. furcula Torréns and Heraty (Brazil) [15].

Neolirata alta and N. daguerrei were collected in northwestern Argentina, and their taxonomic and biological information is given in Torréns and Heraty [15].

3.6.1. Neolirata alta (Walker)

Habitat and location are as follows. Specimens were collected in Los Baños and Rosario de la Frontera (Salta) and Tapia and San Vicente (Tucumán). In Los Baños, the vegetation corresponds to the transition Yungas and Chaco ecoregions, while the others are typical of the Chaco ecoregion (Figure 6(d)). The host plant, Pseudabutilon virgatum, was widely distributed in all four areas (Figure 6(e)).

Life history and host ants are next. The female oviposited about 32 eggs per mm2 at random between the spicules on the underside of a leaf (Figure 6(e)). Eggs hatched within 14 days. The planidia (Figure 6(f)) were mobile and have the ability to jump.

The host ant remains unknown. A few meters from where the female was collected in San Vicente (Tucumán), there was a nest of Ectatomma brunneum. This nest was excavated, but no immature stages were found.

3.6.2. Neolirata daguerrei (Gemignani)

Habitat and location are as follows. Most specimens were collected in Tapia (Tucumán) (Figure 7(c)); the vegetation corresponds to the Chaco ecoregion [40]. The host plant, Urvillea chacoensis Hunz. (Sapindaceae), is a climbing vine distributed throughout the collection area; its leaves are marginally serrate and pubescent [46] (Figure 7(d)).

Life history and host ants are next. Females were observed ovipositing on the underside of leaves of U. chacoensis. A single gravid female oviposited about 28 eggs per mm2 (Figure 7(d)). Eggs hatched within 9 days (Figure 7(e)). Planidia (Figure 7(f)) are very mobile and jump.

Host ant unknown.

3.7. Orasema Cameron

Orasema is composed of 57 species, but many are still undescribed. Their distribution is Neotropical, Nearctic, and Paleotropical [8]. In Argentina, Orasema is widely distributed, with 11 species documented: O. aenea Gahan, O. argentina Gemignani, O. deltae Gemignani, O. freychei (Gemignani), O. gemignanii De Santis, O. salebrosa Heraty, O. simplex Heraty, O. susanae Gemignani, O. vianai Gemignani, O. worcesteri (Girault), and O. xanthopus (Cameron).

Several authors have studied the biological aspects of Orasema [5, 7, 11, 2729, 4756]. Among the genera of ants recorded as attacked by Orasema are Formica Linnaeus, Monomorium Mayr, Pheidole Westwood, Solenopsis Westwood, Temnothorax Mayr, Tetramorium Mayr, Wasmannia Forel, and a dubious case of Eciton Latreille [58, 11, 27, 47, 54]. Immature stages were described by several authors [58, 11, 24, 27, 47, 48, 53, 54, 56, 57].

Herein are summarized the most relevant data on the biology of the species found in Argentina, with new data for O. aenea and some records of an unidentified species.

3.7.1. Orasema aenea Gahan

Habitat and location are as follows. Specimens of O. aenea (Figures 8(a) and 8(b)) were collected in Caimancito (Jujuy). The vegetation and geographic location corresponds to the foothills of the Yungas ecoregion. The host plant, Tecoma stans (L.) Juss. ex Kunth (Bignoniaceae) (common name, Guarán amarillo), is a shrub or small tree that grows 3–6 m tall, with leaves decussate with elliptic-lanceolate and serrated edges, and it blooms from August to October [40] (Figure 8(c)).

Life history and host ants are next. Females were observed ovipositing on the undersides of leaves of T. stans by creating an incision and laying a single egg in short linear rows (Figures 8(d) and 8(e)). Eggs hatched within 9 days. Planidia (Figure 8(f)) crawl and leave the incision but do not have the ability to jump.

Although host ants were not located in the area, the host has been reported as Solenopsis quinquecuspis Forel (Myrmicinae) [27].

Discussion. Plants used for oviposition also include Ilex paraguayensis A.St.-Hil. (Aquifoliaceae) (Yerba Mate) and Olea europaea L. (Oleaceae) (Olive) for which Orasema is considered as a potential pest [50, 57]. Orasema aenea was found on both T. stans and Vaccinium corymbosum L. (Ericaceae) (blueberry), with the latter association recorded by Varone and Briano [29].

3.7.2. Orasema argentina Gemignani

It is associated with Pheidole nitidula Emery (Myrmicinae) [6, 17].

3.7.3. Orasema salebrosa Heraty

It is associated with Solenopsis invicta Buren, S. macdonaghi Santschi and S. richteri Forel (Myrmicinae) [11, 27].

3.7.4. Orasema simplex Heraty

It is associated with Solenopsis richteri, S. invicta, and S. quinquecuspis (Myrmicinae) [11, 27]. Varone and Briano reported Zea mays L., Glycine max L., Vinca rosae L., Citrus limon (L.) Burn, Capsicum annuum L., Smilax campestris Griseb, Paspalum unispicatum (Scribn. & Merr.) Nash, P. denticulatum Trin., P. notatum Fluegge, P. dilatatum Poir, Grindelia pulchella Dann., Stevia aff. entreriensis Hieron, Eupatorium aff. laevigatum L., Sesbania virgata (Cav.) Pers., Asclepias curassavica L., Verbena montevidensis Spreng., Sida rhombifolia L., and Stemodia aff. lanceolata Benth. with oviposition marks of Orasema simplex in nonchoice laboratory tests and in field surveys [29].

3.7.5. Orasema susanae Gemignani

It is associated with Pheidole near tetra Creighton [6].

3.7.6. Orasema worcesteri (Girault)

It is associated with Pheidole radoszkowskii Mayr (Myrmicinae) (=P. nitidula) [17].

3.7.7. Orasema xanthopus (Cameron)

Various aspects related to its biology were recorded by several authors [11, 28, 3039]. Orasema xanthopus is associated with several species of Solenopsis, such as S. invicta [11, 27, 3235, 39, 58], S. quinquecuspis [27], S. richteri [33], and the S. saevissima (Smith) complex [6, 11, 35].

3.7.8. Orasema sp.

Several females were collected in Villa Vil (Catamarca) ovipositing into the stem tissue below the flower buds and along the petiole and midrib of leaves of Lantana xenica Moldenke (Verbenaceae).

3.8. Thoracantha Latreille

This genus is comprised of three species, Thoracantha anchura Walker (Brazil), T. spegazzinii (Gemignani) (Argentina), and T. striata Perty (Argentina and Brazil) [8].

3.8.1. Thoracantha spegazzinii (Gemignani)

A single female was collected on a flower of a Malvaceae. This data was included on the holotype label but not used in the original description of the species by Gemignani [17].

3.8.2. Thoracantha striata Perty

Heraty observed females ovipositing in patches on the underside of leaves of Lantana sp. (Verbenaceae); oviposition took place over 1-2 hours. Eggs and planidia were obtained [8].

4. Conclusion

Eucharitidae are found in almost all biogeographic regions in northern Argentina (Figure 9). Most genera are distributed in the Chaco ecoregion and the transition between Chaco and Yungas, but more surveys are necessary in the Monte and Pampa ecoregions, and in those it was areas never surveyed for eucharitids including Central Patagonia and Prepuna. Herein we presented a new record for Kapala sulcifacies (Cameron) from Salta (Rosario de la Frontera, 20/03/2003; one female and two males deposited in Instituto Fundación Miguel Lillo, Tucumán, Argentina), Lophyrocera plagiata (Walker) from Misiones (Mado, Puerto Magdalena, 23/10/1964; one female deposited in American Museum of Natural History, NY, USA) and Obeza semifumipennis (Girault) from Formosa (Pirané, 31/12/1948; two males deposited in Instituto Fundación Miguel Lillo, Tucumán, Argentina).

Although we have detailed information for most genera, little or nothing is known about the biology of many species. Host relationships were summarized by Heraty [8], Lachaud and Pérez-Lachaud [59], and Lachaud et al. [42]. Herein we presented a new host association for Galearia latreillei from Ectatomma brunneum and confirm the association of Latina rugosa with Odontomachus chelifer suggested by Torréns et al. [25]. Of the remaining genera present in Argentina, ant host relationships can be inferred from species found elsewhere in South and Central America. Generally, it is expected that in Argentina, Orasema (Oraseminae) are exclusively found on Myrmicinae, the genera Lophyrocera, Obeza, and Pseudochalcura attack Camponotini (Formicinae), and the remaining genera in the Kapala clade all attack either Ectatomminae or Ponerinae [8, 9, 11, 12, 23, 26, 27, 29, 42, 43, 59].

Eucharitidae utilize a variety of distinct methods for oviposition. Oraseminae oviposit into incisions made in leaf tissues [2, 5, 49, 52]. Damage to the leaves can be caused by scaring of the plant tissue [7] or through secondary infections caused by the punctures [50]. Because of this, Orasema have been considered as potential pests of banana, citrus, olive, tea, and yerba mate [30, 31, 48, 50, 52, 53]. However, they are never regarded as a continuing pest problem. In contrast, Eucharitinae oviposit either on the undersides of the leaves, into fruits or into the bracts of flower buds, without causing cosmetic damage to the plants. However, as parasitoids of Ectatomma, they might have a negative impact on ants that are potential biological control agents [60]. Importantly, various details of the oviposition behavior, plant and ant host choice, behavior of the planidia both within and outside of the nest, and development within the nest are all key pieces of information to provide a better understanding of how the eucharitids gain access and specialize on their particular ant host group.

Acknowledgments

The author would like to thank J. M. Heraty and P. Fidalgo for their help in all his studies and Elizabeth Murray for constructive comments and suggestions of this paper. This investigation was made possible through funding by the Projects PIP6361 from CONICET and PICT 01238 provided by Agencia Nacional de Promoción Científica y Tecnológica. He dedicates this paper to the memory of Emma “Chongui” Wuscovi who supported him at all times in his Ph.D. degree.