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International Journal of Zoology and Animal Biology Research Article 7 min read

A Comprehensive Key for Identification of the “Swarming Conehead” Ruspolia Differens Serville, 1838 (Orthoptera: Tettigoniidae) Occurring in the Afro-Tropical Region

Matojo ND*
* Corresponding author
ISSN: 2639-216X  10.23880/izab-16000200  Received: December 10, 2019  Published: January 17, 2020
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Keywords
Ruspolia differens R. lezoensis R. nitidula Swarming Coneahead
Abstract

This work reviewed the behavioural, morphological and molecular characteristics of the long-horned grasshopper Ruspolia differens Serville or “senene” in Swahili name (Orthoptera Tettigoniidae), as apparent in literature. On that basis, the work has generated a comprehensive key for identification of this species. As widely known, this insect native to Afro-tropical region where it is widely edible and it has a characteristic swarming behaviour that strikingly occurs during rainy season. Also, it has colour polymorphism with a total of six key sympatric colour forms, sex dimorphism with males possessing longer antennae and a unique pair of active tongue-like metathoracic flaps whereas the females have a corresponding pair of vestigial metathoracic nodules. Furthermore, the species has a pair of distinct subequal black markings on the mid and hind tibia near the knee joint and a white inter-ocular oval mark that appears like a simple eye. Its sister species which is Ruspolia nitidula Scopoli as verified by molecular phylogenetics is exclusively solitary, mostly greenish and Palearctic ranging in Asia, Europe and Northern Africa. Since swarming behaviour is a foremost diagnostic feature differentiating R. differens from other coneheads, it is worthwhile to demarcate the species with a common name “Swarming Conehead” adding to the existed names.

Introduction

The edible long-horned grasshopper, Ruspolia differens Serville, 1838, or “senene” in Swahili name is a well-studied insect species with well-known biology and biogeography. The species belongs to the subfamily Copiphorinae Burmeister in the family Tettigoniidae Krauss, (Syn. Conocephalidae Burmeister) of the order Orthoptera Latreille [1, 2, 3]. The name R. differens is accepted by the International Code of Zoological Nomenclature (ICZN) with nine synonyms namely Conocephalus melanostictus Karny, C. mediotessellatus Karny, C. differens Serville, Homorocoryphus nitidulus subsp. vicinus, C. vicinus, C. exiguus, C. albidonervis, C. lemur, and C. longipennis [4, 5, 6, 7]. Formerly, R. differens was considered a subspecies (Syn. Homorocoryphus nitidulus vicinus) of the Palaearctic species Ruspolia nitidula (Syn. Homorocoryphus nitidulus nitidulus) [1, 2, 8, 9]. The wide understanding of this insect has overcome its taxonomic instability.

Ruspolia differens is a very widespread species throughout the Afro-tropical region, including also some islands of the Indian and Atlantic oceans [10, 11, 12]. Its geographical distribution is particularly linked with the need for a fairly even rainfall with seasonal peaks at regular intervals [5, 7, 10]. The species is widely consumed as a delicacy or crunchy snack in many areas of the world. In recent days, the species has also become a good source of income [12, 13, 14, 15]. Furthermore, R. differens together with other Ruspolia spp. and their New World counterparts (the common coneheads, Neoconocephalus spp.) have been used as experimental animals by biologists investigating mechanisms of hearing, mechanisms of sound production and species specificity [1, 9, 10].

Species Identification

Behavioral Identification the Swarming Behaviour: Ruspolia differens can be identified by its striking swarming behaviour among tettigoniids [5, 7, 9, 11]. The swarming phase which is mainly intended for breeding and migration of the species occurs in wet season when the environmental conditions are favourable [2, 5, 7, 9]. On the other hand, the solitary phase occurs in dry season when breeding and migration events are hindered by the prevailing unfavourable environmental conditions. Studies have also revealed that the seasonal occurrence of swarms is genetically synchronized. In Tanzania, for example, swarms occur in the two rainy seasons per year, that is, November and December (long rains) as well as April and May (short rains).

Morphological Identification

Colour Polymorphism: Ruspolia differens can also be identified by its unique colour polymorphism which apparently comprises at least six key sympatric forms (morphs) namely green, brown, purple-striped green, purple-suffused green, purple-suffused brown) (Figure 1), and purple-striped brown that is very rare. Such pattern has never been reported in any other tettigoniid species. The relative occurrence frequency of these morphs changes with seasonal variation of weather for necessary camouflage of the species and, consequently, the greens dominate during rainy season when greenish vegetation dominates while the browns dominate during dry season when vegetation is largely brown due to dryness.

Figure 1: The key five colour forms of R. differens: 1: Green; 2: Brown; 3: Purple-striped green; 4: Purple- suffused green; 5: Purple-suffused brown Matojo and Yarro, et al. [13]. Paired Male Metathoracic Flaps: Also, Ruspolia differens has a unique sex dimorphism in which males have a smaller body size with longer antennae and a distinct pair of active tongue-like metathoracic flaps (Figure 2) whereas the females have a corresponding pair of vestigial metathoracic nodules.
Click to enlarge
Figure 1: The key five colour forms of R. differens: 1: Green; 2: Brown; 3: Purple-striped green; 4: Purple- suffused green; 5: Purple-suffused brown Matojo and Yarro, et al. [13]. Paired Male Metathoracic Flaps: Also, Ruspolia differens has a unique sex dimorphism in which males have a smaller body size with longer antennae and a distinct pair of active tongue-like metathoracic flaps (Figure 2) whereas the females have a corresponding pair of vestigial metathoracic nodules.

Figure 1: The key five colour forms of R. differens: 1: Green; 2: Brown; 3: Purple-striped green; 4: Purple- suffused green; 5: Purple-suffused brown Matojo and Yarro, et al. [13]. Paired Male Metathoracic Flaps: Also, Ruspolia differens has a unique sex dimorphism in which males have a smaller body size with longer antennae and a distinct pair of active tongue-like metathoracic flaps (Figure 2) whereas the females have a corresponding pair of vestigial metathoracic nodules.

Figure 2: Dorsal view of male R. differens showing distinct paired metathoracic flaps. Matojo and Yarro, et al. [13]. Tibial Black Markings: Ruspolia differens can also be identified by its distinct pair of subequal black markings on the ventrolateral and dorsolateral positions of the mid and hind tibia near the knee joint (Figure 3). The ventrolateral marking is almost two times longer than the dorsolateral marking. Other tettigoniids have no comparable tibial markings.
Click to enlarge
Figure 2: Dorsal view of male R. differens showing distinct paired metathoracic flaps. Matojo and Yarro, et al. [13]. Tibial Black Markings: Ruspolia differens can also be identified by its distinct pair of subequal black markings on the ventrolateral and dorsolateral positions of the mid and hind tibia near the knee joint (Figure 3). The ventrolateral marking is almost two times longer than the dorsolateral marking. Other tettigoniids have no comparable tibial markings.

Figure 2: Dorsal view of male R. differens showing distinct paired metathoracic flaps. Matojo and Yarro, et al. [13]. Tibial Black Markings: Ruspolia differens can also be identified by its distinct pair of subequal black markings on the ventrolateral and dorsolateral positions of the mid and hind tibia near the knee joint (Figure 3). The ventrolateral marking is almost two times longer than the dorsolateral marking. Other tettigoniids have no comparable tibial markings.

Figure 3: The dorsolateral and ventrolateral black markings in the left midtibia of R. differens. Matojo and Yarro, et al. [13]. A White Inter-Ocular Oval Mark: The fastigium of R. differens is separated from the frons by a white inter- ocular oval mark appearing like a median ocellus (i.e. simple eye) just posterior to the sulcus along the median carina (midway the two scapes) (Figure 4). The longitudinal and lateral diameters of this mark are almost one-third of those of the compound eye as described by Matojo, et al. [3].

Figure 3: The dorsolateral and ventrolateral black markings in the left midtibia of R. differens. Matojo and Yarro, et al. [13]. A White Inter-Ocular Oval Mark: The fastigium of R. differens is separated from the frons by a white inter- ocular oval mark appearing like a median ocellus (i.e. simple eye) just posterior to the sulcus along the median carina (midway the two scapes) (Figure 4). The longitudinal and lateral diameters of this mark are almost one-third of those of the compound eye as described by Matojo, et al. [3].
Click to enlarge
Figure 3: The dorsolateral and ventrolateral black markings in the left midtibia of R. differens. Matojo and Yarro, et al. [13]. A White Inter-Ocular Oval Mark: The fastigium of R. differens is separated from the frons by a white inter- ocular oval mark appearing like a median ocellus (i.e. simple eye) just posterior to the sulcus along the median carina (midway the two scapes) (Figure 4). The longitudinal and lateral diameters of this mark are almost one-third of those of the compound eye as described by Matojo, et al. [3].

Molecular Identification

Various molecular data of R. differens have been documented and registered with NCBI (National Centre of Biotechnology Information) global genebank for clear identification of the species using standard approaches. For example, Hemp, et al. documented 16S rRNA partial sequence of the species (Accession number FM882032). Likewise, Matojo, et al. [11] documented 18S rRNA partial sequence of the species (Accession Number KJ001187). Both works successfully verified that the sister species of R. differens is the Large Conehead, Ruspolia nitidula Scopoli, which is an exclusively solitary, mostly green and Palearctic species ranging in Asia, Europe and Northern Africa. Before molecular techniques, the two species were mainly considered conspecific due to their highly close morphological resemblance. Their other nearby relatives includes R. dubia, R. lineosa and R. jezoensis, all being native to Europe and Asia Appendix 1.

Conclusions

Based on the present review, the following conclusions are drawn in relation to R. differens identification: • Ruspolia differens can be easily identified by its distinct five main characteristics as part of “A Comprehensive Key for identification of the Swarming Conehead, Ruspolia differens Serville, occurring in the Afro-tropical region” (see Appendix); the characteristics are swarming behaviour, colour polymorphism, male metathoracic flaps, paired subequal black markings on the mid and hind tibia, and a white inter-ocular oval mark that appears like a simple eye. The molecular relationship of R. differens agree well with its behavioural and morphological characteristics that the closest relative of this insect is the Large Conehead, Ruspolia nitidula which is a non- swarming Palearctic species never reported in East Africa.

Recommendations

  • Since swarming behaviour is a foremost diagnostic feature differentiating R. differens from other coneheads, it becomes worthwhile to demarcate the species with a common name “Swarming Conehead” adding to the existed names.
  • Stakeholders are insisted to be well familiar with the distinguishing characteristics of R. differens for its proper handling, utilization and documentation.

References

  1. Agea JG, Biryomumaisho D, Buyinza M, Nabanoga N (2008) Commercialization of Ruspolia nitidula (Nsenene grasshoppers) in central Uganda. African Journal of Food Agriculture Nutrition and Development 8(3): 319-332.
  2. Bailey WJ (1976) Species isolation and song types of the genus Ruspolia Schulthess (Orthoptera: Tettigonioidea) in Uganda. J Nat Hist10(5): 511-528.
  3. Bailey WJ, McCrae AWR (1978) The general biology and phenology of swarming in the East African tettigoniid Ruspolia differens (Serville) (Orthoptera). J Nat Hist 12(3): 259-288.
  4. Bailey WJ (1979) A review of Australian Copiphirini (Orthoptera: Tettigoniidae: Conocephalinae). Austr J Zool 27: 1015-1049.
  5. Bailey WJ (1975) A review of the African species of the genus Ruspolia Schulthess (Orthoptera, Tettigonioidea). Bulletin de Ins. Fr Afr Noire Ser A 37: 171-226.
  6. Hemp C, Heller KG, Kehl S, Warchaowska liwa E, Waegele W, et al. (2010) The Phlesirtes complex (Orthoptera, Tettigoniidae, Conocephalinae, Conocephalini) reviewed: Integrating morphological, molecular, chromosomal and bioacoustics data. Systematic Entomology 35(3): 554-580.
  7. Ingrisch S (2009) Feedback to catalogue of life: Annual checklist on the classification of Ruspolia differens (Serville, 1838) Catalogue of Life.
  8. Kinyuru JN, Kenji GM, Muhoho SN, Ayieko M (2011) Nutritional potential of longhorn grasshopper (Ruspolia differens) consumed in Siaya District, Kenya. Journal of Agricultural Science and Technology 12: 32-46.
  9. Matojo ND, Jacob GY (2013) Anatomic morphometrics of the “Senene” Tettigoniid Ruspolia differens Serville (Orthoptera: Conocephalidae) from North-West Tanzania. ISRN Entomology Article ID: 176342 pp: 1- 12.
  10. Matojo ND, Keneth M, Hosea (2013) Phylogenetic relationship of the longhorn grasshopper Ruspolia differens Serville (Orthoptera: Tettigoniidae) from Northwest Tanzania based on 18S ribosomal nuclear sequences. Journal of Insects pp: 1-5.
  11. Matojo ND, Njau MA (2009) Plasticity and biosystematics of swarming of the conehead Ruspolia differens Serville (Orthoptera: Conocephalidae) in North-west Tanzania. International Journal of Integrative Biology 9(2): 97-103.
  12. Matojo ND, Yarro JG (2010) Variability in polymorphism and sex ratio of the conehead Ruspolia differens Serville (Orthoptera: Conocephalidae) in North-west Tanzania. International Journal of Integrative Biology 9(3): 131-136.
  13. Matojo ND (2017) A Review Work on How to Differentiate the Longhorn Grasshoppers Ruspolia differens and Ruspolia nitidula (Orthoptera: Tettigoniidae). Journal of Applied Life Sciences International 15(2): 1-4.
  14. McCrae AWR (1982) Characteristics of swarming in the East African bush-cricket Ruspolia differens (Serville) (Orthoptera, Tettigoniidae). J E Afr Nat Hist Soc 178: 1-8.
  15. Ssepuuya, Geoffrey, Mukisa IM, Nakimbugwe D (2017) Nutritional composition, quality and shelf stability of processed Ruspolia nitidula (edible grasshoppers). Food Sci Nutr 5(1): 103-112.
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@article{matojo2020,
  title   = {A Comprehensive Key for Identification of the “Swarming Conehead” Ruspolia Differens Serville, 1838 (Orthoptera: Tettigoniidae) Occurring in the Afro-Tropical Region},
  author  = {Matojo ND},
  journal = {International Journal of Zoology and Animal Biology},
  year    = {2020},
  volume  = {3},
  number  = {1},
  doi     = {10.23880/izab-16000200}
}
Matojo ND (2020). A Comprehensive Key for Identification of the “Swarming Conehead” Ruspolia Differens Serville, 1838 (Orthoptera: Tettigoniidae) Occurring in the Afro-Tropical Region. International Journal of Zoology and Animal Biology, 3(1). https://doi.org/10.23880/izab-16000200
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TI  - A Comprehensive Key for Identification of the “Swarming Conehead” Ruspolia Differens Serville, 1838 (Orthoptera: Tettigoniidae) Occurring in the Afro-Tropical Region
AU  - Matojo ND
JO  - International Journal of Zoology and Animal Biology
PY  - 2020
VL  - 3
IS  - 1
DO  - 10.23880/izab-16000200
ER  -