Stigmacoccus

Hodgson, Chris, Gamper, Heather, Bogo, Amauri & Watson, Gillian, 2007, A taxonomic review of the Margarodoid genus Stigmacoccus Hempel (Hemiptera: Sternorrhyncha: Coccoidea: Stigmacoccidae), with some details on their biology, Zootaxa 1507, pp. 1-55 : 25-27

Stigmacoccus species C

( Fig. 10 )

Material studied. MEXICO, Carrizal, Michoacan, 27.i.1926, on "Tepehuaje", no collector ( USNM): 1/5 cysts, 2 large (complete) + 3 small, all missing anal areas.

Unmounted material. Not seen.

Mounted material. More or less circular; length large about 1.5 mm, small about 1.13 mm.

Dorsum. Derm densely covered in dermal spines except over a large area medially (densest on large specimens); with a few along anterior margin of head; intersegmental areas within spines reasonably distinct; each spine mainly 20–35 ųm long. With a few short, cone-like spines associated with each abdominal spiracle, each about 10–12 ųm tall and most about 2x as tall as wide, distributed as follows: large: I–VII 3–11 and VIII 0; small: I–V 2–5, VI–VIII missing. Setae: (i) hairs all slightly sunken, each 14–18 ųm long; sparse; (ii) hair-like setae not detected; (iii) minute setae of 2 sizes: basal socket about 3 ųm wide + a very short seta about 1 ųm long, sparse; larger setae, each about 2–3 ųm long: most frequent amongst cone-like spines near spiracles. Pores: (i) bilocular pores, each rather round and about 12–13 ųm widest, clearly larger than tubular pore; each in a shallow dermal depression: quite frequent, mainly intersegmental on abdomen; and (ii) tubular pores, each 8–9 ųm wide and 11–14 ųm deep; rather abundant throughout and 3 or 4 times as frequent as bilocular pores on large specimens. Abdominal spiracles, large: outer atrium 30–33 ųm long, 35–38 ųm wide, each with 2 rows of pores at distal end; inner atrium 16–20 ųm long, 28–30 ųm wide, with a further short atrium at distal end, 8 ųm long; small: outer atrium 18 ųm long, 18 ųm wide, each with 1 row of pores at distal end; inner atrium 12 ųm long, 13 ųm wide, short atrium at distal end, 3 ųm long. Anal area missing on small specimens: large: anal opening 100 ųm wide, with about 16 small pores around outer margin; tuberclelike pores in a band about 4–5 pores deep, each tubercle about 8 ųm tall and 4 ųm wide, plus an outer ring of rounded bollard-like spines 1–2 spines deep, each spine about 7 ųm wide, each with a rather flat apex; outer diameter of band of bollard-like spines 170–175 ųm; abdominal spiracles VIII lying within or just laterad to outer ring of bollard-like spines. Anal tube large: outer tube about 220 ųm long, and finger-like extensions each 160 ųm long; distribution and shape of pores on anal tube as in generic description.

Venter. Distribution of spines similar to that on dorsum. Pore and setal distribution similar to that on dorsum. Antennae without setae or small pores on derm near margin; width: large 23–25 ųm, small 16 ųm. Clypeolabral shield pointing posteriorly, length: large each 310–330 ųm, small 235–250 ųm; labium facing more or less anteriorly, large of unknown length but 200 ųm wide, small 136–200 ųm long, 140–165 ųm wide. Thoracic spiracles: peritreme large each 38–42 ųm wide, with 1–2 rows of moderate-sized pores totalling about 19–27; length of muscle plate 120–130 ųm; small 20–23 ųm wide, with 9 or 10 pores; muscle plate 75– 82 ųm long; each spiracle with a group of cone-like spines similar to those near abdominal spiracles, each group elongate but almost all spines on posterior margin, few or absent along anterior margin; large with 20– 40; small with 10–16; each group also with a few larger setae.

Comment. These cysts resemble those of Stigmacoccus sp. B above but differ in having (i) cone-like spines (rather than bollard-like spines) near each spiracle; (ii) cone-like spines near each thoracic spiracle much more abundant along posterior margin than anterior margin; and possibly in having (iii) more abundant bilocular and tubular pores.

Discussion of cyst stage. Mouthparts: on most specimens, the labium was pointing anteriorly, either overlying the clypeolabral shield or anterior to it. The clypeolabral shield appears to lie within the body of the cyst and appears to be only rather loosely connected to it – indeed, it is missing on many specimens. When present on mounted specimens, the clypeolabral shield may point in almost any direction although, when the labium overlies it, it is generally facing posteriorly (i.e., in the normal position). When the clypeolabral shield is facing anteriorly, the labium, when present, is generally some way anterior to it. When the clypeolabral shield is missing, the labium is also generally missing as well, suggesting that it is also only rather loosely connected to the cyst wall. It is unclear as to how the stylets emerge through the cyst wall!

Cyst sizes. As far as the authors are aware, two cyst sizes have not been noted previously for Stigmacoccus species. Gullan and Brookes (1998) recorded two sizes of cyst with Callipappus rubiginosus (Maskell) , where the larger (19 mm long and 7 mm wide) contained a female and the smaller cysts (each about 11 mm by 5 mm) were considered to enclose male nymphs. Foldi (2005) outlined the life cycle of the ground pearl genera ( Margarodidae ), illustrating this as including 2 cyst stages in both male and female life cycles, although he states that Margarodes vitis (Phillipi) may have three stages. Morales (1991) stated and illustrated Coelostomidea wairoensis (Maskell) and Ultracoelostoma brittini Morales as having two non-mobile feeding stages in the female life cycle but only one in the male, where the 2nd-cyst stage is a mobile non-feeding prepupa. However, it should be noted that Jakubski (1965) considered that there were several moults during the cyst stage of Porphyrophora , although Vahedi (2002) doubted this. Foldi (1997b) confirmed that the cyst wall of margarodoids was formed of many layers mainly formed from anal fluids, but that these do not equate to exuviae. As far as Stigmacoccus are concerned, there would appear to be three possibilities: either (i) the two sizes represent different instars, so that the small cysts refer to instar II and the large cysts to instar III (both sexes); (ii) as for (i) but where the male has only one cyst stage (small), which moults to give rise to the prepupa; or (iii) the differences refer to the sex, the small cysts being male and the larger cysts female. This is discussed further under biology in the final discussion.

Cysts in other taxa. Cyst stages appear to be restricted to the more "primitive" margarodoid families, namely Matsucoccidae , Margarodidae , Xylococcidae , Stigmacoccidae and Callipappidae. This group of families was found to be sister to the remaining non-cyst forming margarodoid families by Hodgson and Foldi (2004) based on the morphology of their adult males. A cyst stage is found also in the Steingeliidae, one of the reasons why this taxon is sometimes included in the margarodoid family group.

Comparison of cysts of Stigmacoccus species. All the above cysts are rather similar with the exception of that of S. garmilleri , which has the broad band of sclerotisation lying outside the spiracles on abdominal segment VIII.

Figures

FIGURE 10. Cyst stage of Stigmacoccus species C, from Mexico. For lettering, see Fig. 5.