A New Species of the Mealybug Genus Mirococcus (Hemiptera: Coccomorpha: Pseudococcidae) from the Cape Verde Islands, with New Records and an Updated Checklist of Scale Insect Species

Simple Summary In this study, a new mealybug species from the Cape Verde Islands, Mirococcus capeverdensis Łagowska and Hodgson sp. n., collected on Campylanthus glaber Benth. (Scrophulariaceae) is described and illustrated based on the adult female. A key to the mealybugs from the Afrotropical Region that lack cerarii is provided. In addition, seven scale insect species are recorded for the first time from the Cape Verde Islands. An updated checklist of Coccomorpha species from this region, along with their known island distributions and valid sources, is also appended. Prior to this study, 38 scale insect species in 7 families and 28 genera are known from the Cape Verde Islands. Abstract In this study, a new species of mealybug from the Cape Verde Islands, Mirococcus capeverdensis Łagowska and Hodgson sp. n., collected on Campylanthus glaber Benth. (Scrophulariaceae), a native plant to these islands, is described and illustrated based on the adult female. A taxonomic key to the mealybugs from the Afrotropical Region that lack cerarii is provided. In addition, seven scale insect species, namely Aulacaspis tubercularis Newstead, Hemiberlesia cyanophylli (Signoret), Pseudaonidia trilobitiformis (Green), Icerya aegyptiaca (Douglas), Maconellicoccus hirsutus (Green), Palmicultor palmarum (Ehrhorn), and Pseudococcus comstocki (Kuwana) are recorded for the first time from the Cape Verde Islands and an updated checklist of Coccomorpha species known from this region, along with their known island distributions and valid sources, is appended.


Introduction
The Afrotropical region has a unique and diverse scale insect fauna with 1458 species distributed on the African continent and its many oceanic islands, including the Cape Verde archipelago [1].
The Cape Verde volcanic archipelago is a group of 10 major islands plus several smaller uninhabited islets located in the central Atlantic Ocean, approximately 570 km off the western coast of the African continent, to the west of Senegal, Gambia, and Mauritania. It lies between 14 • to 18 • N latitude and 22 • to 26 • W longitude and forms part of the Macaronesia ecoregion, along with the Azores, the Canary Islands, Madeira, and the Savage Isles. The total land area is approximately 4033 km 2 , with the islands of Santiago (785.0 km 2 ) and Santo Antão (785 km 2 ) being the largest. Three of the Cape Verde islands, Sal, Boa Vista, and Maio, are fairly flat, sandy, and dry; the others are generally rockier with more vegetation. Cape Verde's climate is milder than that of the African mainland, with average daily high temperatures ranging from 26 • C in February to 31 • C in September, whilst the average annual rainfall ranges from less than 100 mm in the arid coastal areas to more than 1000 mm in the humid mountains. Vegetation in the islands is similar to that Generic diagnosis. Members of the genus Mirococcus can be diagnosed by the following combination of features: antennae eight or nine segmented (rarely seven); legs usually normally developed; claw usually with a denticle; anal apparatus complete in type species, but much simplified in other species; posterior pair of ostioles always present, anterior pair sometimes absent; multilocular and trilocular pores present; quinquelocular pores present or absent; oral collar tubular ducts usually simple; oral rim ducts absent; cerarii absent, and conical setae absent [13]. Comment. Mirococcus is one of the few genera of mealybugs that completely lack cerarii and conical setae. Species found within the African continent lacking cerarii can be separated using the key below. Paratype: Data are the same as for the holotype, a single adult female but broken in two, with each half mounted on separate slides. The anterior half is poor, and the posterior half is good. All three slides were deposited in BMNH, London. (Figure 1). Data for paratype in brackets. Appearance in life not recorded. Mounted adult female 1.3 mm long and 0.5 mm wide. Anal lobes small, each with a long apical seta 118-126 (118) µm long, plus several other setae, each 50-76 (55) µm long; anal lobe bar absent. Antennae eight (nine) segmented, each approximately 223 (252) µm long. Legs well developed, with lengths (iii) in µm: coxa 90-95 (116-120), trochanter + femur 168 (189); tibia 144 (151), and tarsus 84-86 (84); tarsal digitules setose; claw approximately 26-28 (27) um long, with a strong denticle; claw digitules knobbed, longer than claw; translucent pores present on distal end of femur and on tibia. Labium approximately 100 µm long; clypeolabral shield with a single pair of long setae. Spiracles with anterior peritreme 25 (32)(33)(34) µm wide, posterior peritreme 32 (42) µm wide. Circulus well developed, approximately 50 (92) µm wide, possibly divided by an intersegmental line. Ostioles present, with few trilocular pores on lips and no setae. Cerarii absent but with very long setose setae (lengths ranging from 35 µm to 60 µm) in groups of one to three along margin, located approximately segmentally. Each group also with one to three shorter setae, each approximately 25-35 µm long.

Description of adult female
Comment. Mirococcus is one of the few genera of mealybugs that completely lack cerarii and conical setae. Species found within the African continent lacking cerarii can be separated using the key below.
Mirococcus capeverdensis Łagowska and Hodgson sp. n.   Dorsal surface with rows of setae, some very short (only about 8 µm long) but also with a few setae similar to long marginal setae, each 40-50 (40-50) µm long with a few on all segments. Multilocular disc pores, each 6-8 µm wide, frequent throughout but most abundant posteriorly; where present mainly along posterior margin of each segment; those posteriorly all with 10 loculi, but number of loculi decreasing more anteriorly, with five or six loculi in some smaller pores. Quinquelocular pores otherwise absent. Trilocular pores slightly larger than usual, almost round, each 3-4 µm wide, and present throughout. Simple pores, each approximately 1.5 µm wide, present sparsely throughout. Oral collar tubular ducts, each 8-10 µm long, present throughout but most abundant posteriorly and marginally. Oral rim ducts absent.
Ventral surface with mainly slender setose setae but with an occasional quite long seta, as on dorsum. Multilocular disc pores as on dorsum, throughout but most abundant on abdomen; where present mainly along both anterior and posterior margins. Trilocular pores, as on dorsum, evenly distributed. Simple pores as on dorsum. Oral collar tubular ducts present, as on dorsum, but more abundant and present more or less throughout. Oral rim ducts absent.
Etymology. The name of the species is derived from Cape Verde Islands, the archipelago from which this species was collected, with the adjectival suffix -ensis, indicating the place of origin.
Comment. Adult female M. capeverdensis sp. n. can be diagnosed by a combination of the following features: (i) all cerarii and conical setae absent; (ii) dorsum, margin, and venter with very long setae, each up to 60 µm long; (iii) small anal lobes; (iv) legs with translucent pores; (v) each claw with a strong denticle; (vi) multilocular pores present on both dorsum and venter; (vii) oral collar tubular ducts all about the same size, present on dorsum and venter, and; (viii) trilocular pores slightly larger than usual, almost round.
M. capeverdensis sp. n. differs from all other species in this genus in having very long setae on the dorsum and margin.
Of the species currently included in Mirococcus, adult female M. capeverdensis sp. n. are most similar to that of M. inermis (Hall), sharing the following features: (i) cerarii and conical setae absent; (ii) circulus well developed; (iii) both anterior and posterior ostioles present; (iv) legs with translucent pores; (v) simple pores scattered on the dorsum and venter; (vi) multilocular pores present on the dorsum and venter, and (vii) oral collar tubular ducts of one size present on the dorsum and venter. However, it differs as follows (character-states in M. inermis in brackets): (i) many dorsal setae, very long and setose (all dorsal setae short and slender), (ii) claw digitules capitate (claw digitules setose), and (iii) claw with a strong denticle (claw denticle weak).
With the description of M. capeverdensis sp. n., the total number of species in Mirococcus is increased to 15, distributed mainly in the Palaearctic Region (14 species). Currently, only two Mirococcus species are known from the Afrotropics: M. inermis (Hall), recorded from north Africa (Egypt, Sudan, and Tunisia), and M. capeverdensis sp. n. from the Cape Verde Islands. [14] and Millar [15]).

1.
Dorsal setae and ventral marginal body setae very stoutly spiniform with apices rounded or truncated, and some slightly curved. Antennae nine segmented. Hind leg without translucent pores. Claw with a denticle. Quinquelocular pores present . . .

Checklist of Coccomorpha from Cape Verde Islands
In addition to the new species described above, the samples of scale insects collected on the Cape Verde Islands in 2018 by the first author also included 7 species new to the fauna and 11 species which had been reported earlier by Fernandes [4][5][6][7], Schmutterer et al. [8], and Van Harten et al. [9].
The species new to the Cape Verde islands in the list below include notes regarding their economic importance and worldwide distribution. In addition, an updated checklist of Coccomorpha species known from this archipelago, along with validation sources, is appended (Table 1). Families and species within each family are listed in alphabetical order according to the classification used in the ScaleNet database [1]. The references to species recorded from the Cape Verde Islands reported in ScaleNet have been checked and, where erroneous, corrected in the present checklist.  [1]. Its origin is probably southern Asia, where it is common, but it has spread into Africa, the Malagasian area, and tropical America [20]. Tetraena fontanesi (Zygophyllaceae); Heliotropium curassavicum (Boraginaceae) and Tamarix senegalensis (Tamaricaceae). Distribution: A polyphagous species widespread throughout southern Asia, Australia, and Africa [20]. Palmicultor palmarum (Ehrhorn, 1916) Material examined: Sal, Santa Maria, 5.ii.2018, 17.ii.2018, 11 ♀♀on palms; Santo Antão, 6.ii.2018, 5 ♀♀on an unidentified plant. Distribution: Widely distributed in the Australasian, Oriental, and Palaearctic regions. It has also been reported from the Nearctic and Neotropics [1,11,18,[25][26][27]. This is the first report from the Afrotropical Region. Tamarix senegalensis [6,9] this publication

Discussion
Following the current study, 48 scale insect species are known from the Cape Verde Islands: 18 Diaspididae, 11 Pseudococcidae, 13 Coccidae, 2 Asterolecaniidae, 2 Monophlebidae, 1 Dactylopiidae, and 1 Ortheziidae (Table 1). This updated checklist includes all the scale insect species recorded from the Cape Verde Islands according to ScaleNet [1], plus the eight species reported here for the first time. However, Orthezia urticae (L.) is erroneously recorded in the ScaleNet catalogue, citing Van Harten et al. [9], but neither they nor any of the other authors who have studied the fauna of these islands, such as Fernandes [4][5][6][7] and Schmutterer et al. [8], mention it as being present. The list above also includes a further three diaspidid species (Aonidomytilus albus (Cockerell), Duplachionaspis natalensis (Maskell), and Pinnaspis buxi (Bouché)) which have been omitted from the ScaleNet database, although there are published records in Schmutterer et al. [8] and Van Harten et al. [9].
In addition to the new Mirococcus species described above, there may be other undescribed species in the various lots of material previously collected on these islands. Van Harten et al. [9] noticed an undescribed species of Planococcoides (which would now be placed in Formicococcus), which he considered had probably been introduced from mainland Africa. Van Harten et al. [9] also collected a Ceroplastes species, which they considered similar to but different from C. rusci (L.). It may have been these specimens from the Cape Verde Islands that were seen by Hodgson and Peronti [28], who also considered the specimens not to be C. rusci (L.) but possibly referable to one of the other cryptic species in this group.
Apart from M. capeverdensis, the newly recorded scale insects in the present study are all widely distributed, polyphagous species and considered to be plant pests. Thus, the cosmopolitan Aulacaspis tubercularis is a serious pest of mangos in many parts of the world [34][35][36]; Hemiberlesia cyanophylli causes damage to various ornamentals and avocado trees, while Pseudaonidia trilobitiformis was recorded as a pest of cocoa in The Democratic Republic of the Congo [1]. Another species, Icerya aegyptiaca, is considered a pest of Artocarpus altilis (Breadfruit) in the Pacific Region [23]. In addition, all the newly recorded mealybug species are known to cause some damage; thus, Maconellicoccus hirsutus is a potentially invasive pest of several crops, particularly pineapple [1]. Palmicultor palmarum attacks the leaves of oil palm and can kill young germinating plants [1,11], and Pseudococcus comstocki is a pest of many fruit and ornamental trees in the U.S.A. and Japan [1]. Although none of the above mentioned species were very abundant, each could potentially be important both ecologically and economically on the Cape Verde Islands.