Parasaissetia nigra (Nietner)

Adult female is elongate-oval, shiny, dark brown, 3-4 mm long. Body shape varies according to the substrate, specimens found on leaves are broad, only slightly convex but much more convex than those on stems or leaf-mid-ribs, which are elongate and less convex. Immature stages and young adult specimens of P. nigra are translucent-yellow and sometimes mottled (Hamon & Williams 1984).

In California and Florida, P. nigra has 1 complete generation per year outdoors (Gill 1988). Ben-Dov (1978) recorded up to 6 generations per year in greenhouses in Israel. In Tamaulipas, Mexico, from Oct 2012 to Jun 2013, we observed the development of at least 2 complete generations of P. nigra on mistletoe Phoradendron spp. (Santalales: Santalaceae) near Rio San Marcos in Ciudad Victoria. Upon hatching, the first instar nymphs (crawlers) move away from the female to other parts of the plant, where they fix themselves and start feeding.

It is interesting that in natural landscapes in Tamaulipas, scale colonies developed on mistletoes, hemiparasitic plants from the genus Phoradendron, but not on Acacia farnesiana (L.) Willd., Guazuma ulmifolia Lam., Salix humboldtiana Willd. and Prosopis glandulosa Torr., which have been reported as host plants of this species. In Mexico, P. nigra was recorded as pest of guava (Ben-Dov 1978). Moreover, parasitoids were obtained only from P. nigra on huisache Acacia farnesiana (L.) Willd. in the State of Tamaulipas.

Families of parasitoids of Parasaissetia nigra

Parasitoids from several families of Chalcidoidea have been reported as natural enemies of P. nigra in the world: Encyrtidae, Aphelinidae, Eulophidae, Eupelmidae and Pteromalidae. In Peru, the dominant parasitoid species in agroecosystems belong to 3 families: Encyrtidae, Aphelinidae and Pteromalidae (Núñez 2008). In many countries where it was once a pest, P. nigra is now successfully controlled by natural enemies originally introduced to control Saissetia oleae (Bartlett 1978). For example, the most effective control agent of P. nigra in California (USA), is an encyrtid Metaphycus helvolus (Compere), that was introduced with several other enemies to control S. oleae, which has been more effective against P. nigra (Ebeling 1959).

In Mexico, we reared from P. nigra parasitoids from 6 families: Encyrtidae, Aphelinidae, Eupelmidae, Eulophidae, Pteromalidae and Signiphoridae, but the encyrtid and aphelinid species were the most dominant. This is the first record of Signiphoridae as parasitoids of P. nigra. The main parasitoids in the family Aphelinidae are species of the genus Coccophagus Westwood.

Coccophagus spp.—parasitoids of Parasaissetia nigra

Species of the genus Coccophagus are mainly parasitoids of soft scales (Coccidae), but rarely parasitize armored scales (Diaspididae) and other Coccoidea. In the world, the genus Coccophagus consists of 257 species (Noyes 2012a), some of which are widely distributed. In the family Aphelinidae, Coccophagus is the second most speciose genus after Encarsia Foerster. Coccophagus is divided into 6 species-groups: lycimnia-group, pseudococci-group, varius-group, malthusi-group, ochraceus-group and zebratus-group (Hayat 1997).

Females of this genus have 8-segmented antenna; mandible with 1 or 2 teeth and a truncation; pronotum entire, medially sometimes narrow; mid lobe of mesoscutum with numerous short setae; axillae large, strongly projecting forwards, with at least 2 setae, rarely more to about as densely setose; Each side lobe with 4 or more setae, rarely less; scutellum large, usually convex, not overlapping propodeum, either with 3 pairs of setae or several additional setae to densely setose; propodeum either medially membranous or with a triangular median projection: fore wing large, broad, densely setose, with short marginal fringe; submarginal vein with 5 or more setae, stigma vein variable, either subsessile or with a neck and swollen stigma; linea calva absent; hind wing usually broad, with a broadly rounded apex; all tarsi 5-segmented; hind coxae sometimes large, as long as femora; tibiae often with thick setae (bristles) along dorsal (outer) margins; gaster with 7 terga; length of ovipositor and relative dimensions of last tergum highly variable; hypopygium extending to about two-thirds along gaster and with apex broadly rounded or truncate; color of body variable from whitish-yellow to brown black, partially or entirely; males similar to females except for genitalia and, in most species, antennae quite different from those of females.

Coccophagus females are diploid, developing from fertilized eggs, but are also produced from unfertilized eggs, whereas the males are invariably haploid, produced from unfertilized eggs; males are either primary ectoparasitoids, secondary ectoparasitoids or endoparasitoids of other primary hymenopterous parasitoids, including females of the same species (Hayat 1997). For example, females of C. caridei (Brèthes) are soft scale parasitoids, but males develop in the mealybug Planococcus citri (Risso) as hyperparasitoids of the encyrtid Anagyrus pseudococci (Girault) (Flanders et al. 1961).

Twenty-four species of Coccophagus have been recorded as parasitoids of P. nigra, and of these some species have a worldwide in distribution due to various introduction programs (Hayat 1997; Noyes 2012a). An analysis of the lists of species distributed in some large regions — South Africa, Oriental and Neotropical, and United States according to Noyes (2012a), showed that these regions have a similar number of Coccophagus species that parasitize P. nigra: In addition to the widespread parasitoid species some regions have 1-2 specific parasitoids from their local fauna: South Africa — 1 from a total of 12 species, the Oriental Region — 1 of 8 species, and the Neotropical Region — 2 of 13 species (Table 1). In the South Africa list, some species of Coccophagus were included by Hayat (1997): C. bivittatus Compere, C. lutescens Compere, C. modestus Silvestri, C. nubes Compere, C. saintbeauvei Compere and C. varius Silvestri.

Table 1.

Coccophagus parasitoids of Parasaissetia nigra and their distribution in the world (after Noyes 2012a).

In Tamaulipas, Mexico, we reared the following 5 Coccophagus species from P. nigra: C. rusti Compere (introduced into Mexico accidentally from California, where it was introduced for Saissetia oleae), C. lycimnia (Walker), C. ochraceus Howard, C. minor sp. nov. and Coccophagus sp. As Table 1 shows, 2 other species of Coccophagus (C. pulvinariae and C. scutellaris) are widely distributed in the world; in Mexico, they are parasitoids of other coccid species: C. lycimnia from Philephedra lutea (Cockerell), Coccus hesperidum L., Pulvinaria spp. and Saissetia spp. (Myartseva et al. 2012).

Below is presented a key to species of Coccophagus associated with P. nigra in Mexico, including C. scutellaris and C. pulvinariae, species present in Mexico as parasitoid, of other soft scales that probably also attack P. nigra. All these species are distributed in the Neotropical Region and USA (California).

Figs. 1–4.

Coccophagus minor sp. nov., female: 1 — antenna, 2 — stigmal vein, 3 — mid tarsus and mid tibial spur, 4 — ovipositor.

Table 2.

Structural differences of three Coccophagus species.