Redescription of the red-striped soft scale, Pulvinaria tenuivalvata (Newstead), with a new synonymy (Hemiptera, Coccomorpha, Coccidae)

Abstract The soft scale, Pulvinaria tenuivalvata (Newstead, 1911), is a major pest of sugarcane in Egypt. This paper provides a redescription and illustration of the adult female based on a microscopic study of the morphology of several adult female specimens and of the type series illustrated by De Lotto (1965) on citronella grass from Uganda. Two paratypes of Pulvinaria saccharia De Lotto, 1964 are also studied and the name is placed here as a junior synonym of Pulvinaria tenuivalvata.


Introduction
Sugarcane, Saccharum officinarum L. (Poaceae) is one of the main crops in Egypt, and the control of pests on this crop is very important. The red-striped soft scale Pulvinaria tenuivalvata is a major pest since 1992, when it was observed for the first time and named as Pulvinaria elongata Newstead (Karam and Abou-Alkhair 1992). It attacks leaves, causing a major reduction in crop yield due to depletion of sap, production of honeydew and growth of sooty mould. Early and heavy infestations have resulted in complete yield lost (El-Serwy et al. 2008).
The species was described by Newstead (1911) as Lecanium tenuivalvatum, based on adult females, all of which were heavily parasitisied, infesting citronella grass (Cymbopogon citratus) in Uganda. De Lotto (1964) described and illustrated for the first time Pulvinaria saccharia collected on leaves of sugar cane in Durban, Natal, and stated that the species is structurally very closely related to Pulvinaria tenuivalvata (Newstead, 1911). The same author (De Lotto 1965) redescribed and illustrated the adult female of Pulvinaria tenuivalvata from a single specimen from the type locality and the type host plant. Williams (1982), in his study of Pulvinaria iceryi (Signoret) and its allies on sugarcane and other grasses, separated P. tenuivalvata from five Pulvinaria species, giving a key and commenting on the great similarity of these five species, P. elongata Newstead, P. iceryi (Signoret), P. saccharia De Lotto, P. sorghicola De Lotto and P. tenuivalvata (Newstead). He stated that P. tenuivalvata is very close to P. saccharia. Watson and Foldi (2002) discussed the identity of the pest on sugarcane in Egypt and identified the species as Pulvinaria tenuivalvata (Newstead), although it had previously been identified as Pulvinaria elongata Newstead (Karam and Abu-Elkhair 1992) and Saccharolecanium krugeri (Zehntner) (Ali et al. 1997). In 2001, Ghabbour and Hodgson described and illustrated the 1 st instar nymph and 2 nd and 3 rd instar female nymphs of P. tenuivalvata and provided a key.
The present paper redescribes and illustrates the adult female of Pulvinaria tenuivalvata (Newstead) in detail. In addition, we were able to study two paratypes of Pulvinaria saccharia De Lotto, 1964 and conclude that the name Pulvinaria saccharia is a junior synonym of the name Pulvinaria tenuivalvata.

Materials and methods
Slide-mounted adult females were studied from the entomology collections at The Natural History Museum, London, U.K. (BMNH) and Muséum national d'Histoire naturelle, Paris, France (MNHN). The photos were produced using with a Leica DFC 420 camera and the software Leica Application Suite, version 2.8.1. The drawings were made using the software Illustrator CS6 version 16.0.0. Morphological terms follow those by Hodgson (1994) and Qin and Gullan (1992).
Host plants. The main host plant in Egypt is sugarcane, Saccharum officinarum, but it has also been recorded from several other Poaceae in Egypt: Imperata cylindrica, Sorghum vulgare saccharatum, and Zea mays. The species is known on Cymbopogon citratus (citronella grass) and Pennisetum purpureum in Uganda (García Morales et al. 2016), and from Zimbabwe and South Africa (Natal), on Saccharum officinarum (as P. saccharia).
Comments. Two paratypes of Pulvinaria saccharia De Lotto, 1964, have been examined, both adult females. The dorsal setae are short, strong and spiniform, but certainly not lanceolate as stated by the previous authors (De Lotto 1964;Williams 1982). The claw digitules are unequal, one much thicker than the other one, but of the same length. This character was first observed by De Lotto (1964;1965) and confirmed by Williams (1982) and Watson and Foldi (2002). These two paratypes show the presence of three types of ventral submarginal tubular ducts, as always. Pulvinaria saccharia has ventral multilocular disc-pores on the metathorax and the mesothorax. The range of setae between the anterior and the posterior spiracles is about 29-31. The combined length of hind trochanter plus femur is about 200-220 µm. On the appearance in life of P. saccharia, De Lotto (1964) mentioned that "P. saccharia does not form any ovisac but a thin layer of white cottony wax laid beneath the body along the margin". A similar type of ovisac on adult females of P. tenuivalvata was observed in Egypt. All these characters fall within the range of the morphological characters of P. tenuivalvata, so P. saccharia is here treated as a synonym of P. tenuivalvata.
for his technical assistance. We are indebted to David Ouvrard, Natural History Museum, London (NHM)who facilitated the loan of material of Pulvinaria species essential to this study. Many thanks to Douglas J. Williams, NHM, for his constant advice.