Arumatia dubia

Sexuality of the species All specimens of Arumatia dubia gen. et comb. nov. reared by us from different localities are parthenogenetic and no males are known so far. Additionally, we did not find any specimen that could represent a male of A. dubia in the visited collections matching the known or an expected distribution of the species. This is also true for iNaturalist photographic records. It is quite likely that Arumatia gen. nov. presents exclusively natural parthenogenetic populations or even entire species, which is a possible and previously recorded condition for phasmids such as is known for most or some species in the genera Acanthoxyla in New Zealand (Uvarov 1944; Myers et al. 2013) or Bacillus Berthold, 1827 in Europe (Berthold 1827; Scali et al. 2003). All sightings of A. dubia in nature consisted of females even when found in abundance. A factor that could be related to the evolution of parthenogenesis in this lineage is the short egg incubation period observed for A. dubia (2 – 3 months). The eggs of facultative parthenogenetic individuals or populations of sexual phasmid species take considerably longer to hatch (Bedford 1978; VMG, PWE & PABAN pers. obs.). Another possible factor is the absence of a praeopercular organ, contrasting with its presence in A. aramatia gen. et sp. nov. and A. motenata gen. et sp. nov., both species with known males. This organ serves as an attachment for the male vomer so a historical absence of males could have led to the loss of such a structure. Arumatia anyami gen. et sp. nov., A. diamante gen. et sp. nov. and A. crassicercata gen. et sp. nov. are also known by females only, the former also lacking a praeopercular organ. This might suggest parthenogenesis to be present in other species of Arumatia gen. nov. as well. Biology In Chapadão do Sul (MT), Assis (SP) and Araguari (MG), specimens were found in natural areas feeding on plants of the subfamily Mimosoideae (Fabaceae). In captivity, they also fed on the Fabaceae plants Anadenanthera Speg. spp. and Parapiptadenia rigida (Benth.) Brenan (angico trees), Chamaecrista flexuosa (L.) Greene (sensitive pea), the Myrtaceae plants Psidium guajava L. (guava) and Eugenia uniflora L. (Brazilian cherry), and the Sapindaceae plant Serjania Mill. sp., all native to Brazil and occurring in the Cerrado and adjacent biomes. Several reared specimens were observed to drastically change colour between green, orange or brown. This change was observed both gradually during moults and in adult specimens that changed colour in a few days. The female V 0561 from Ibaté (SP) was orangish when pre-subadult (Fig. 13 A) and turned green when adult (Figs 2 D – E, 13 B). The female V 0547 from Araguari (MG) was light green when found already as an adult (Fig. 2 C) and later turned greenish brown (Fig. 1 A, adult individual) and to orangish brown before dying (Figs 6 A, 7 A – C, 13 I). The female V 0561 was kept in an open area from the fifth instar until adult from 16 April 2021 to 17 August 2021 with access to ca 10 plant vases, including the host plant species C. flexuosa and P. guajava. The insect was observed every day and night. It hid in typical camouflage posture during the day (Fig. 2 D – E) and foraged at night, never going further than one meter from the host plants. At night, even if not walking away from the spot where it stayed by day, it kept its body away from the resting surface and held the antennae up and apart (similar to specimens in Fig. 2 A, C). During daytime, it usually hid in different spots, among leaves and branches either atop, on the side or under branches, near the surface of cactuses (Fig. 2 E) or large leaves, on the side of vases and less frequently on a thin branch with all legs close to the body (Fig. 2 D). The guava plant was strongly preferred, as the phasmid totally ignored the sensitive pea most of the nights. The insect fed on parts of random leaves of the guava plant, and a few times on some leaves and flowers of the sensitive pea. When handled, both nymphs and adults of Arumatia dubia gen. et comb. nov. display agitated behaviour, quickly walking frenetically away without stopping, which also happens frequently when the rearing cage is opened. Eggs of this species have a somewhat short incubation period with most eggs hatching within 50 – 70 days and having a high hatching rate (> 70 %). Eggs require infrequent watering to hatch with higher rates resulting from spraying 2 – 3 × to 0.5 – 1 × a week, which configures a lesser humidity requirement in comparison with many other phasmids from Southeast Brazil (pers. obs.). Some eggs were tracked for development: seven of a few dozen eggs laid in 18 – 30 January 2021 by female V 0547 from Araguari hatched 6 – 10 April 2021; only four nymphs survived and moulted from first to second instar from 2 to 5 May 2021; from second to third in the period 23 – 25 May 2021; from third to fourth on 18 June 2021; from fourth to fifth in the period 10 – 14 July 2021; and from fifth to sixth in the period 9 – 12 August 2021, when they became adults. Three nymphs that hatched around 10 December 2021 from the stock from Ibaté were also tracked, presenting a quicker development probably due to the warmer season in which they developed: they moulted to second instar from 28 December to 4 October; to third instar in the period 9 – 16 October; to fourth from 16 to 30 October; to fifth from 30 October to 12 November; and to sixth from 11 to 25 November.