First records of the minor pest termite Eucryptotermes hagenii ( Müller , 1873 ) ( Blattodea , Termitoidae , Kalotermitidae ) from the Chaco Dominion in Argentina

Eucryptotermes Holmgren, 1911, comprises 2 species of Neotropical drywood termites with phragmotic head soldiers. We report the presence of Eucryptotermes hagenii (Müller, 1873) in native forests of the Chaco Dominion and Chaco Province, enlarging its distribution and recording the genus and species for the first time in Argentina. Eucryptotermes hagenii abundance was estimated as intermediate by standardized sampling. Eighteen morphometric characters were measured in soldiers and alates, and 9 of them provided new data. The colonies, located inside living trees trunks and dead wood, were composed of reproductives, soldiers, pseudergates, and immatures.


Introduction
Eucryptotermes Holmgren, 1911, is a little-known and highly specialized endemic Neotropical genus of "drywood termites" that live in trees and pieces of wood.Soldiers have truncated heads with a remarkable degree of phragmosis (Krishna 1961).This genus has only 2 described species, the type species, E. hagenii (Müller, 1873), and E. breviceps Constantino, 1997.These two species were previously known only in Brazil, in the Brazilian and Chaco Subregions, respectively (Araujo 1977, Constantino 1998, Krishna et al. 2013).
The published data on E. hagenii are few and include some biological and cytogenetic aspects, as well as its pest status.Most of records of E. hagenii are from natural habitats in southeastern Brazil, but it is also known from urban areas, such as Curitiba and Blumenau, which indicates that it could be an occasional structural pest (Constantino 1997(Constantino , 1998)).In the city of São Paulo, where the most significant termite damage is caused by Cryptotermes Banks, 1906 andCoptotermes Wasmann, 1896, E. hagenii is considered to be a minor urban pest (Fontes 1995, Constantino 2002).From a cytogenetic and evolutionary point of view, this species is unusual because it has the lowest number of chromosomes so far reported for termites, with 2n = 22 (Martins and Mesa 1995).
We report for the first time the presence of E. hagenii in natural habitats in the Chaco Dominion in Argentina.Our new records enlarge the known range of this species and also provide new information on its biology and morphometry.

Methods
The samples were collected as part of a research project on termite communities in the Humedales Chaco Ramsar Site at the Los Chaguares Reserve (Colonia Benítez, Chaco province, Argentina) between September 2016 and February 2017 (Fig. 1) (27°20.00′S,058°58.03′W).The Reserve (19 ha) is located in an area with humid mesothermal climate and little winter rainfall, where the average annual temperature is above 18 °C.Biogeographically, it belongs to the Chaco Subregion, Chaco Dominion, Chaco Province, Eastern Chaco District or Humid Chaco Ecoregion and is characterized by the presence of grasslands, floating islands ("embalsados"), gallery forests, and xerophytic forests (Morrone 2014).The vegetation in the study area is a riverbank forest with trees up to 15 m high (Cabrera andWillink 1973, Cabrera 1976).
The standardized sampling protocol for termites (Jones and Eggleton 2000) was applied, consisting of 2 transects, each 100 × 2 m, that are divided into 20 contiguous sections (5 × 2 m).Termites were collected in each section (1 person/h) in various microhabitats, including fallen tree trunks and branches, mounds, and arboreal nests.Twelve samples of surface soil (12 × 12 cm, 10 cm deep) were excavated in each section.The total number of termite encounters per transect was counted.
The abundance of E. hagenii was estimated in the surveyed areas, defining their occurrence, dominance and abundance patterns according to the categories established by Florencio and Diehl (2006).To determine the occurrence pattern, the species are categorized as rare (R: present in 1-10% of sections), sporadic (S: 11-40% of sections), common (C: 41-70% of sections), frequent (F: 71-99% of sections), and constant (CS: 100% of sections).The following formula was applied: OP = numbers of sections where the species was found × 100/total number of evaluated sections.For the dominance pattern, the species are classified as rare (R: 1-10% of encounters), accessory (A: 11-49% of encounters), and dominant (D: 50-100% of encounters), according to the formula DP = number of encounters of each species × 100/total number of encounters.The combination of both patterns is used as an indicator of the abundance of each species, according to the following categories: common (C: species with CS and D patterns), intermediate (I: species with R, S, C or F and A and species with S, C, F or CS and R), and rare (R: species with R in occurrence and dominance patterns).
Voucher specimens were preserved in 80% ethanol and deposited in the FACENAC (registration numbers 2512-2518).The specimens were collected under the authorization of the Dirección de Fauna, Parques y Ecología, Chaco Province.
In soldiers and alates, 18 morphometric characters (Roonwal 1970, Scheffrahn andKřeček 1999) were measured with a micrometric eyepiece attached to a Leica EZ4 stereomicroscope.Microphotographs were taken with a Canon EOS Rebel T3 digital camera coupled to the microscope.For scanning electron microscopy, the specimens were dehydrated in a conventional ethanol series, air-dried, gold-coated, and photographed with the SEM Jeol 5800 LV from the UNNE Microscopy Service.The map was elaborated by using QGIS Essen version 2.14 (QGIS 2016).6) have a dark brown, short, and broad sub-truncated or phragmotic head, with almost straight parallel sides and a slight constriction at the antennae level.The frontal region of the cephalic capsule is extended forward, forming a sharp circular ridge or frontal flange located dorsally between the vertex and the frons and between the frons and the genae on both sides.The antennae are inserted at about one-third or one-half of the length of the head from the front sides (Fig. 4).The mandibles are partially covered by the cephalic capsule in dorsal view, and its inner edge is slightly serrated without notable teeth.The pronotum is brownish yellow with its anterior margin rising abruptly in profile, emarginated, and strikingly serrated (Fig. 5).The alates of E. hagenii have a uniformly brownish yellow coloration and transparent wings (Fig. 7).The pronotum is narrower than the head.The anterior margin of the forewing scale is almost straight or very slightly convex and forewings have all major veins emerging independently at the wing suture.The 18 morphometric characters measured on E. hagenii soldiers and alates are presented in Table 1.

New
Eucryptotermes breviceps differs from E. hagenii by its smaller soldiers and imagoes and by having only 2 tibial spurs on the fore-tibiae.Soldiers of E. breviceps also have a shorter and strongly phragmotic head, with a much larger frontal extension covering most of the mandibles in dorsal view (Constantino 1997).
Other kalotermitid genera detected in Argentina, with soldiers showing varying degrees of cephalic phragmosis are Cryptotermes, Glyptotermes Froggatt, 1897, and Tauritermes Krishna, 1961, but the development of their frontal ridge is smaller than in Eucryptotermes (Silvestri 1903, Torales et al. 1997, Roisin 2003).In addition, unlike them, the antennae of Eucryptotermes are inserted at about one-third or one-half of the head length from the front sides.

Discussion
In our surveys of termites in native forests of the Humedales Chaco Ramsar Site, E. hagenii was collected and identified from the Chaco Dominion, Chaco Province, Chaco Humid District for the first time (Fig. 1).In this biome, E. hagenii is a sporadic species, because 6 colonies were detected in the 2 transects (12.5% of the analyzed sections).With regard to dominance, it was an accessory species (15.79%), so that the abundance of E. hagenii in the analyzed forests was categorized as intermediate.Other 2 colonies of the species were detected in the Reserve during complementary samplings.
We found only 2 nests in Colonia Benítez that had 1 or 2 dealate reproductives.Presumably these are members of the royal couple and suggest that the colonies were monogynous.In November, 7 mature alates were found in a single nest.The mature alates found in November indicate that swarming might take place in late spring or early summer.All colonies were also composed of sol-  diers, pseudergates, and immature individuals (larvae and white soldiers) (Fig. 7).For E. hagenii, there are few data available on the microhabitats occupied by E. hagenii in natural habitats, such as inside a dead hardwood trunk in a Rio de Janeiro forest (Araujo 1970).This species does not construct conspicuous arboreal nests like some termitids, and thus, its detection is difficult and requires exhaustive searching of standing trees and pieces of dead wood.We found this species in galleries excavated inside the trunks of living trees (Fig. 8) and in standing dead wood, as well as in fallen branches.Native trees having colonies of E. hagenii were found to be Nectandra megapotamica (Spreng.)Mez and E. contortisiliquum (Vell.)Morong.Fallen branches sheltering E. hagenii were poorly degraded, and the wood still retained its structure, although some had high moisture content.
Eucryptotermes, like other "drywood termites", have evolutionary characteristics that are considered basal for termites in regard to their morphology, social organization, and nesting type.Nevertheless, the phragmotic head of soldiers is an advanced or derived condition within the family Kalotermitidae; with the addition of prominent mandibles, it is developed as a defensive adaptation to block galleries in the wood and prevent the entry of predators (Krishna 1961, Scheffrahn et al. 1998).
Nine of the 18 morphometric characters measured in soldiers and alates of E. hagenii provide new data for the species; our measurements of the other 6 characters extend previously known ranges (Constantino 1997).Our measured values correspond to observations of Constantino (1997), who pointed out that the size of the soldiers varied considerably.His sample size was small, and species were previously thought endemic to Brazil.The number of termite genera in Argentina is increased to 34 (Silvestri 1903, Torales et al. 1997, 2005, Roisin 2003).