Possible New Species of Araecerus (Coleoptera: Anthribidae) associated with Mastixiodendron pachyclados (Rubiaceae) of Papua New Guinea
Abstract
Araecerus is genus of beetles of the Anthribidae family which are important economic pests of various crops including coffee (Rubiaceae), with A.fasciculatus (Degeer) being the common pest (weevil) of coffee beans. This paper presents a study in which five undescribed species of genus Araecerus were reared predominantly from the seeds of M.pachyclados (Rubiceae), a native tree of Papua New Guinea (PNG). Fruits of M. pachyclados were regularly sampled and insects attacking them were reared, preserved and identified. Fruits were hand collected, photographed, weighed and reared. Insects emerging from the fruits were captured and preserved in 99% ethanol. All the specimens were identified into morphospecies at the laboratory. The five new species discovered were designated as A. sp.1, A. sp.2, A. sp.3, A. sp.4 and A.sp.5. This was accorded based on differences in body length; scutellum color, size, hair-scales and visibility; length of first and second segments of fore tarsus; apical and subapical teeth-size (mandible and maxillary palpi); declivity of dorsal abdomen; basal-anterior eye markings; lateral eye markings; absence of eye markings; and shape of pygidium. We discovered A. sp.1 has yellowish gold marking inside the base of the eye, A. sp.2 with pygidium almost vertically-flat at abdominal apex, A. sp.3 has eyes without yellowish gold marking and generally dark in color, A. sp.4 with distinct yellowish gold interior-lateral marking in its eye, and A. sp.5 with pygidium pointed at abdominal apex.
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Introduction
Araecerus is a genus of beetles belonging to the family Anthribidae. They are important storage pests of cash crops such as coffee (Rubiaceae) and cocoa (Malvaceae). The species A. fasciculatus (DeGeer) is a common storage pest of coffee beans (coffee bean weevil) (Barrera 2008). A. fasciculatusis also a common pest infesting cocoa beans in storage (Eduku2014).
Duke (1993) mentioned that A. fasciculatus was one of the pest of Nutmeg. A. fasciculatus was reported by Abo and Ja (2014) as major pests of yam and cassava flour. Araeceruslevipennis Jordan is a pest of leguminous plant Leucaenaglauca (L.) that has high protein content that is mainly used as a valuable foraging crop in ranches (Sherman and Tamashiro1955).
Early entomologists like Pascoe (1860) and Jordan (1894) extensively described about one hundred genera and one thousand species under Anthribidae family in which A.Schönherr, (Valentine 2005) was categorized under Subfamily Choraginae and Tribe Araecerini. Choraginae subfamily consisted of 3 species in South America in comparison with 14 species in Central America (Blackwelder1947). Jordan (1907) described ten species while Valentine (1999; 2002) contributed to the revision of the species. At least 98 species of Choraginae existed in the Old World (Mermudes and Lesche, 2014). The first species of the tribe Araecerini is A.fasciculatus (DeGeer1775), a pluralistic species of the genus A.Schoenherr, 1823 that comprises of about 70 described species in Indo Pacific (Mermudes2015).
Ctvrtecka et. al. (2014) obtained 1200 specimens of Anthribidae as a part of Curculionoidea in the same location where our research was carried out, but they could not be reliably identified to species. Seven species were found but had to be excluded also because most of the specimens remain unsorted (Ctvrtecka et. al.2014). Morimoto (1972) described A.Schoenherr as having tarsal segment 3 bilobed, nearly as broad as segment 2; tarsi slender, segments 1 and 2 much longer than wide; front tibiae simple at least in female; front tarsi normal; lateral prothoracic carinae reaching the middle; front tarsal segment 1 longer than the remaining segments added together; and eyes oval, less prominent.
This study was carried out to discover host-specific new species of Araecerus associated with M.pachyclados (Rubiaceae) using its “fallen fruits”.
Conclusion
The genus Araecerus is a major pest of important cash crops (e.g. coffee and cocoa) and identification of new pests and quantification of their abundance are prerequisites to crop protection. It is known now that A. fasciculatus was found feeding on pesticide plant Meliaazedarach L., which may support their ability to tolerate application of botanical pesticides. In such case, more suitable and effective control measures should be used to overcome such problems. Since these five species have not been described, it is presumed that they are possibly new species. Their morphological descriptions can therefore be used for nomenclatural system, and thus contributes to overall insect taxonomy.