Monday, January 27, 2020

[Entomology • 2020] Pseudolebinthus lunipterus • A Striking Deaf and Mute New Cricket (Orthoptera, Gryllidae, Eneopterinae) from Malawi

Pseudolebinthus lunipterus 
 Salazar, Murphy, Guillaume, Nattier & Robillard, 2020 

This article presents an intriguing new cricket species of the tribe Xenogryllini discovered in Northern Malawi. This is the first case of mute and deaf species in the subfamily Eneopterinae; it shows no stridulatory apparatus on short male forewings and no tympana on either side of fore tibiae in both sexes. We introduce the new species and its complete mitogenome and assess phylogenetic relationships based on molecular data obtained from next-generation sequencing genome skimming method. Phylogenetic analyses place the new species within the genus Pseudolebinthus in Xenogryllini, as the sister species of Pseudolebinthus gorochovi Robillard. We describe Pseudolebinthus lunipterus sp. nov., provide illustrations of main morphology, male and female genitalia, photographs of living specimens and information about habitat and update the identification key for species of genus Pseudolebinthus. We discuss the differences between the new species and related taxa and the striking loss of acoustic communication in this cricket.

Insecta Linnaeus, 1758
Orthoptera Olivier, 1789
Gryllidae Laicharting, 1781
Eneopterinae Saussure, 1874

Xenogryllini Robillard, 2004

Genus Pseudolebinthus Robillard, 2006
Type species: Pseudolebinthus africanus Robillard, 2006

Figure 1: Pseudolebinthus lunipterus sp. nov.
 (A) Male habitus on low vegetation at night; (B) natural habitat indicated by a green arrow (left) and location of Malawi on simplified map of Africa (left); (C) type locality in Malawi. Photo Tony Robillard.

Pseudolebinthus lunipterus sp. nov.

Diagnosis: Size small, mostly dark brown with pale wings (Figs. 1, 3 and 4). Among Eneopterinae genera, the new species presents the characteristics of Pseudolebinthus: large lateral eyes (Figs. 5A–5C); brachypterous FWs barely reaching quarter of abdomen length in males (Figs. 4 and 6), shorter in females where it forms pale narrow crescents (Figs. 4 and 5D); male genitalia with long sclerotized lophi, close to that of P. gorochovi (Figs. 8 and 9); female ovipositor little differentiated but less pointed and thicker than in P. gorochovi (Fig. 10A). The new species is characterized by complete absence of tympana (unique feature among eneopterines) (Figs. 7A and 7B), absence of stridulatory apparatus on male FWs (Fig. 6), abdomen ventrally yellow with a wide black stripe (Fig. 5F), thick and short female ovipositor (Fig. 4D), and differences in male genitalia, including shape of pseudepiphallic parameres, shape of sclerite in ectophallic fold and endophallic apodeme with anterior lateral expansions.

Type locality. North Malawi, Mount Uzumara, ..., 1,941 m.

Distribution. The species is only known from the type locality in Northern Malawi (Fig. 1C).

Etymology. The species name refers to the whitish wings, rounded in males and crescent-shaped in females, which look like tiny moons on the back of the dark body of these crickets when encountered at night.

Habitat and life history. Pseudolebinthus lunipterus lives on low vegetation in herbaceous areas near forest hedge or in open areas along trails in forest (Figs. 1A and 1B). Adults and juveniles have been found active at night on top of vegetation, but can also be found lower within vegetation during the day. Remarkably, the species lives in syntopy with P. gorochovi in the type locality, where adults and juveniles of both species are quite abundant. One juvenile specimen of P. lunipterus has been observed eating a dead insect on a low leaf on vegetation (Fig. 11B).

Females maintained in controlled laboratory conditions (20–22 °C, 14–10 day–night cycle) with a single male produced 46–50 offspring (n = 2) during their life; first hatchings started 42–49 days after first mating and occurred on a period of 35–66 days.

Figure 11: Live photos of Pseudolebinthus lunipterus sp. nov.
(A) Female on vegetation; (B) subadult male eating a dead insect on a leaf at night; (C) first instar juvenile. Photos (A and B) Tony Robillard and (C) Karen Salazar.

Conclusion: Crickets of Malawi
The diversity of crickets in Eastern Africa in general, and Malawi in particular, has been underestimated, understudied and undersampled. This is at least the case for the members of the tribe Xenogryllini which were recently revised (Jaiswara, Dong & Robillard, 2018, 2019; Jaiswara et al., 2019). Despite the large amount of data considered in these systematic studies (several hundreds of specimens studied across the study of the largest natural history museum collections), they gathered very little information about the species of Pseudolebinthus, known by a few specimens each.

A single recent field trip in Malawi allowed us to re-discover two of the previously described species of the genus, which are in fact common species, and it allowed documenting the acoustic features of their calling songs and their ecology (T. Robillard et al., 2020, in prep.). Interestingly, these findings allowed us to discover P. lunipterus, a completely different new species belonging to the Xenogryllini lineage, but with strikingly new morphological features. This finding reveals that more taxa probably remain unrecorded in the whole Eastern African region, as suggested by the large amount of new species and genera recently discovered in this region for other clades of orthopteran insects (Hemp et al., 2018; Hemp & Heller, 2019). More taxonomic surveys with appropriate collecting methods in regions where there is zero record about these crickets, such as other regions of Malawi, but also Zimbabwe, Zambia, Western Mozambique and Northern South Africa, are thus necessary to explore this part of African biodiversity.

Karen Salazar, Raymond J. Murphy, Marion Guillaume, Romain Nattier and Tony Robillard​. 2020. 
Pseudolebinthus lunipterus sp. nov.: A Striking Deaf and Mute New Cricket from Malawi (Orthoptera, Gryllidae, Eneopterinae). PeerJ. 8:e8204. DOI: 10.7717/peerj.8204