Nylanderia deceptrix

Nylanderia deceptrix is an obligate social parasite of Nylanderia parvula.

Identification
Queen: smallest of Nearctic Nylanderia (TL less than 3.5 mm); mesosoma color mottled with areas of lighter and darker brown to yellowish-brown; Male: very small, nonfunctional wings present.

Distribution based on Regional Taxon Lists
Nearctic Region: United States.

Biology
Messer, Cover and LaPolla (2016) - Queen: smallest of Nearctic Nylanderia (TL less than 3.5 mm); mesosoma color mottled with areas of lighter and darker brown to yellowish-brown; Male: very small, nonfunctional wings present.

Nylanderia deceptrix can be identified from other Nearctic species because it has the smallest queens of all Nearctic Nylanderia, ranging between 2.91–3.40 mm (Trager 1984, Kallal and LaPolla 2012). Compared to other Nearctic species with no macrosetae on the scape such as Nylanderia parvula and Nylanderia trageri (Kallal and LaPolla 2012), N. deceptrix is the only species with queens showing bicoloration, with the head and gaster being darker in color than the mesosoma. Additionally the queens have a mottled coloration on the mesosoma with areas of darker brown and yellow-brown. Nylanderia deceptrix males are currently the only Nearctic Nylanderia to display highly reduced wings. The male parameres display dense and very long macrosetae compared to those of other Nearctic species. The digitus displays a narrower area towards the base of the structure that expands towards the tip and ends with a narrow point. The end of the digitus also has distinct foveolate (pitted) sculpturing. The head of both the queen and the male are worker-like in overall appearance (except for the presence of distinct, large ocelli; never strongly developed in workers), and are longer than wide, whereas Nylanderia reproductives, especially queens, typically have wider than long heads. Ad-ditionally, Nylanderia queens usually have heads covered in dense pubescence, and this is not the case in N. deceptrix.

Messer, Cover and LaPolla (2016) - Nylanderia deceptrix has not been observed to produce a worker caste (we observed no features among the thousands of N. parvula workers examined that would indicate N. deceptrix workers were present; i.e. all conformed to the expected worker morphology of N. parvula), it is functionally polygynous, host-queen tolerant, and has only been found within colonies of N. parvula. The intermediate size of N. deceptrix queens between that of N. parvula workers and queens is a morphological indication of its obligate social parasite status, as obligately socially parasitic ants are smaller than their host queens (Buschinger 2009). They are also often the size of their host workers but that is not the case with N. deceptrix. The males of N. deceptrix have highly reduced wings and cannot fly, a trait seen in several obligate social parasites such as Tetramorium atratulum, Pheidole inquilina, Plagiolepis xene, and Pogonomyrmex colei.

Nylanderia deceptrix seems to have a much more restricted range than its host and resides in an area with a high density of host colonies, traits that appear to be common among obligately socially parasitic species (Heinze 1989, Nonacs and Tobin 1992, Savolainen and Vepsäläinen 2003). The likelihood of a restricted range is enhanced by the fact N. deceptrix queens either have very poor flight capability, or do not fly at all, coupled with the fact that males have very small, non-functional wings. The incidence of colonies parasitized with N. deceptrix supports this as well, since all the colonies were clustered in close proximity to one another. The presumed poor flight capability coupled with the observed clustering of parasitized colonies leads us to suspect that N. deceptrix disperses by walking to nearby host colonies.

Once at a host colony, the data presented here suggest it is difficult for N. deceptrix to become established in a N. parvula colony if that colony does not already possess N. deceptrix queens. Our aggression data shows that N. parvula workers act very aggres-sively towards any individual (N. parvula worker or N. deceptrix queens) from a colony already parasitized with N. deceptrix. Comparatively, N. parvula displays lower aggression towards N. parvula workers from colonies not parasitized with N. deceptrix.

Conversely, when an individual from a colony containing N. deceptrix encounters an individual from a different colony that also contains N. deceptrix, the aggression that results is noticeably lower. This suggests that N. deceptrix is influencing the amount of aggressive behavior displayed by N. parvula. This decrease in aggression could also be responsible for acceptance of N. deceptrix queens from one colony into another foreign colony already containing N. deceptrix.

Myles Standish State Forest in southeastern Massachusetts is the only known location of Nylanderia deceptrix. The forest itself is open canopy, largely composed of pitch pine (Pinus rigida), bear/scrub oak (Quercus ilicifloia), and very sandy soil.

Within Myles Standish State Forest collections were along Southeast Line Road (41°49.12'N, 70°39.75'W, elev. 31 m) a sandy horse trail, in June, July and September of 2013 and May, June, July and September of 2014. During these trips, colonies were excavated, and then collected and/or observed for data collection purposes described below.

Prevalence of host species and parasitism rate Across the seven transects, the average Nylanderia parvula nest entrance density was 2.35 nest entrances/m2 (SD=0.15), ranging from 1.64–2.64 nest entrances/m2 for the individual transects.

In total, 356 N. parvula colonies were excavated and checked for the presence of Nylanderia deceptrix. Of those 356 colonies, nine had N. deceptrix present, resulting in a parasitism rate of 2.53%. The number of N. deceptrix queens found in a single colony ranged from 1–8 per colony. Nylanderia deceptrix males were only found in one of the nine parasitized colonies, and contained a total of nine males. Nylanderia deceptrix brood were found in two of the nine parasitized colonies. One colony contained only a single N. deceptrix queen pupa. On the other end of the spectrum one colony contained 74 N. deceptrix queen pupae and 4 N. deceptrix male pupae (male N. deceptrix pupae could be determined by highly reduced wing buds and the presence of genitalia).

Reproductive cycle Among 43 colonies, the average number of adult N. parvula reproductives (alate queens and males) found in colonies was: 15.4 (±23.3) for May, 0 for June, 6.1 (±4.1) for July, and 20.4 (±11.77) for September. Compared to the number of alates, the total brood (larvae and pupae combined) within colonies shows the opposite trend. Counts were low in May (37 ±134.2) and September (15.8 ±209.6), moderate in July (177.6 ±65.2), and at the highest in June (722.7 ±116.1). Nylanderia parvula reproductive pupae were only found in July, and N. deceptrix reproductive pupae were only observed in July as well.

Morphology
Messer, Cover and LaPolla (2016) - Forewing length (FWL) measurements: The FWL:WL for N. parvula ranged from 2.27–2.59, with an average of 2.47 (±0.018), and for N. deceptrix the ration ranged from 2.07–2.31, averaging 2.18 (±0.014). The difference between the two was significant (P<0.00001, t=12.59 for a two-tailed test), meaning the wings of N. deceptrix were smaller in proportion to Weber’s length compared to N. parvula.

Nomenclature

 *  deceptrix. Nylanderia deceptrix Messer, Cover & LaPolla, 2016: 55, figs. 2-11 (q.m.) UNITED STATES.

Queen
(n=10): TL: 2.91–3.40; HW: 0.55–0.63; HL: 0.58–0.69; EL: 0.22–0.24; SL: 0.73–0.78; MW: 0.52–0.57; PW: 0.55–0.67; WL: 0.99–1.07; GL: 1.24–1.69; PDH: 0.35–0.42; PFL: 0.67–0.72; PFW: 0.15–0.17; SMC: 0–3; PMC: 4–5; MMC: 21–27; MtMC: 3–4.

Indices: CI: 92–97; REL: 33–37; SI: 121–130; FI: 21–24.

Overall brown to yellowish-brown; head and gaster darker brown with generally lighter mesosoma; mesosoma color mottled with areas of lighter and darker brown to yellowish-brown; antennae, mandibles and legs yellow; body covered with dense pubescence; macrosetae dark brown but usually with lighter yellowish-brown tips. Eyes bulge slightly beyond head outline in full-frontal view; three prominent ocelli present. Scapes long; yellow; exceed posterior margin of the head by the length of first 3 funicular segments; scapes with dense pubescence and sometimes with up to three short standing macrosetae, but often with none. Head with abundant macrosetae and layer of pubescence; slightly longer than broad; becoming slightly wider at posterior of head. Mesosoma covered with erect macrosetae and pubescence; most macrosetae on mesonotum and metanotum show strong curvature. Gaster covered in pubescence and a large cluster of macrosetae on first gastral tergite.

Male
(n=5): TL: 1.91–2.05; HW: 0.45–0.46; HL: 0.48–0.53; EL: 0.17–0.18; SL:0.57–0.59; MW: 0.28–0.32; PW: 0.37–0.39; WL: 0.66–0.69; GL: 0.74–0.88; PDH: 0.24–0.26; PFL: 0.52–0.54; PFW: 0.11–0.13; PL: 0.20–0.24; SMC: 0; PMC: 0; MMC: 7–12; MtMC: 1–2. Indices: CI: 88–97; REL: 34–36; SI: 125–127; FI: 22–25.

Overall color brown to brownish-yellow; head and gaster darker brown with generally lighter mesosoma; antennae, mandibles, legs, and parameres yellow; body covered with dense pubescence; macrosetae dark brown but usually with lighter yellowish-brown tips; cuticular surface dull, covered in a dense layer of appressed setae. Head longer than broad; eyes large and bulging beyond head outline in full-frontal view; three prominent ocelli present; scapes long, exceeding posterior margin of the head by length of first 3 funicular segments; scapes absent of macrosetae and with a dense layer of pubescence; clypeus roughly rectangular, with anterior margin emarginated; mandible broad, with 4 teeth; all but apical tooth are weakly developed; apical tooth distinct, curves in toward body midline. Mesosoma relatively small; very small nonfunctional wings present; mesosoma covered in pubescence, with erect setae of varying lengths dorsally and on legs. Pronotum collar-like; mesonotum offset from pronotum at sulcus; mesonotum rises sharply above height of pronotum; mesonotum flat dorsally with many erect setae of varying lengths; marcosetae on mesonotum and metanotum show strong curvature of about 90°; propodeum indistinct from remainder of mesosoma, but with steep declivity; petiole short, triangular, upright, with posterior face only slightly longer than anterior face. Gaster with a dense layer of pubescence and erect setae; parameres especially setose; parameres roughly triangular, turning slightly mesad posteriorly; long setae extend off of parameres; cuspi small and tubular, reaching digiti dorsally; digiti weakly anvil-shaped, with poorly developed point directed ventrally; volsellar lobes flat, slightly indented relative to digital margin.

Type Material
Holotype queen, USA. Massachusetts: Plymouth County: Myles Standish State Forest; Southeast Line Road; 41°49.12'N, 70°39.75'W; elev. 31 m; in N. parvula nest; 06 June 2013 (S. Messer) ; 10 paratype queens and 7 paratype males same locality information as holotype except different collection dates (MCZC and ).



Etymology
The species epithet deceptrix (Latin = deceiver) is attributed to the parasitic lifestyle, deceiving the host to allow cohabitation.