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References: de Piña (1977); Marín and Cisneros (1977); Quispe (1983); Bustamante (1986); Vargas (1988); Velasco (1988); Cruz (1990); Méndez (1992); Montiel (1995).

References: de Piña (1977); Marín and Cisneros (1977); Quispe (1983); Bustamante (1986); Vargas (1988); Velasco (1988); Cruz (1990); Méndez (1992); Montiel (1995).

prey on both wild cochineal and D. coccus remain to be examined.

Morphology and Life Cycle

Like other coccids, cochineal is characterized by sexual reproduction and sexual dimorphism. From the nymph I stage to the first molt, it is difficult to distinguish between the male and the female (Gunn 1978). Cytogenetically, however, males and females are quite different from the embryonic stage onward (Nur 1989; Aquino P. et al. 1994), as females have a diploid chromosome number and males are physiologically haploid. Paternal chromosomes, which look like a heterochromatic mass, are known as H chromosomes (Nur 1989). These chromosomes are inactive, but their presence is necessary for embryo viability, fertility, and sexual differentiation (Chandra 1962).

The morphology and life cycle of D. coccus have been extensively studied (Table 13.2). The male has a six-stage life cycle (egg, nymph I, nymph II, prepupa, pupa, adult), while the female has only four stages (egg, nymph I, nymph II, adult). Life cycle duration, morphology, and size of D. coccus are variable, depending on many factors, such as population density, host species, nutritional level of the host, soil quality where the host grows, light, and temperature. Despite this variability, certain characteristics are common. The egg is oval and shiny bright-red. Hatching may occur inside the adult female, or the crawlers may hatch 10 to 32 minutes after the eggs are laid. Nymph I is red and oval when recently hatched, but after a time becomes covered by a white powdery wax called coccicerin, characteristic of the species.

From 2 to 12 days after the first molt, the male as nymph II, now clearly distinct from the female, constructs a cocoon of filamentous wax. (Wild cochineal males build their cocoons on the same day as the molt.) In the prepupa stage, the antennae are relatively thick and curved backward, genitalia are distinguishable, and most meiotic activity and the greatest development of the testicles occur. In the pupa, the antennae have grown; the legs are now long and slender and lack nails. Dorsally, the segmentation of the abdomen can be seen, and ventrally the genitalia can be observed. The adult male is approximately 2.2 mm in length with a wingspan of 4.8 mm (wild cochineal males are considerably smaller). The body sections are clearly distinguishable. The antennae are moniliform (tapering), composed of 10 beadlike segments. Other features of the adult include: three pairs of simple eyes; no buccal apparatus; a pair of simple-veined, mid-thoracic wings; slender legs with a single nail; and a pair of white, waxy appendages, measuring up to 3.6 mm in length. Cruz (1990) reports that a male mates with only one to three females; reproductive efficiency is considerably reduced after more than two matings.

The nymph II female does not change form; the duration between nymph II and adult varies from 8 to 25 days (Table 13.2). The adult female is oval, 4 to 6 mm long, and 3 to 5 mm wide. Segmentation of the prosoma is barely evident (De Lotto 1974). Legs and antennae are well developed but small. The rostrum is made up of three segments (De Lotto 1974; Montiel 1995). The body has numerous (15) cuticular pores, both on the dorsum and on the abdomen, this being the characteristic commonly used by taxonomists to classify the species (Ferris 1955; De Lotto 1974). The anal ring is recognized as a modification of segment 10; it is dorsal, has a half-moon shape, and is membranous on the anterior margin and sclerotic on the posterior margin (De Lotto 1974; Montiel 1995). Receptivity or sexual maturity occurs within 3 to 22 days. Pre-oviposi-tion lasts from 24 to 68 days and oviposition is from 10 (when separated from the host) to 58 days. The total biological cycle of the female lasts from 64 to 150 days; during that time, a female may lay over 400 eggs.

Although it is not clear whether parthenogenetic reproduction is possible for Dactylopius spp., sexual reproduction is necessary for D. coccus and D. confusus. Hence, the ratio between the sexes should be 1:1 (Cruz 1990; Gilreath and Smith 1987). However, the ratio is modified by temperature (Mendez 1992) and photoperiod (Montiel 1995), generally favoring the female (Marín and Cisneros 1977). At least for D. ceylonicus and D. coccus, weather changes, especially low temperature and drought, as well as population density, affect the male population.

Host

The age of the cladodes selected and their utility for cochineal production depend on the species and variety of nopal, environmental conditions, and especially the hydration of the cladode, the quality of the soil, and the relative humidity. One-year-old, peripheral cladodes provide the most favorable conditions for cochineal establishment (Flores 1995). Five or six different kinds of nopal were utilized in Mexico for cochineal production in the 16th century. In time, most of these varieties were introduced into the West Indies and Europe. The most important nopal species for the raising of cochineal has always been O. ficus-indica, with its different varieties; Nopalea cochinellifera has also been used, but not in Mexico (Donkin 1977). Nutritional levels of nopal also affect the establishment and productivity of cochineal and its carmine content (Arteaga 1990; Vigueras and Portillo 1995). Indeed, oxalate crystals in host tissue can influence the population of cochineal (Castillo 1993).

Spines apparently have no influence on the establishment of D. coccus. Nevertheless, Piña (1981) indicates that, both in Mexico and in South America, cochineal occurs naturally on spiny nopal species, and under cultivation, the spiny species are more productive. Portillo (1995) reaffirms the greater adaptability of D. coccus to spiny varieties. Nevertheless, the nopal cacti most commonly utilized for the rearing of cochineal are spineless, for the obvious advantage of plant management. Only a weak relationship exists between the establishment of cochineal insects and stomatal frequency or the thickness of the cuticle, epidermis, and hypodermis (Castillo 1993).

Environmental Factors and Natural Enemies

Data from Mexico and other parts of the world indicate that environmental factors influence the growth and development of the cochineal insect (Piña 1977, 1981; Cruz 1990; Méndez 1992; Flores 1995; Tekelenburg 1995; Table 13.3). Important climate hazards include frosts, high temperatures (above 30°C), rainfall with its washing effects, and wind, all of which restrict the establishment of nymph colonies on the host plants. Biological hazards of the cochineal insect include predators and parasitoids, both for natural populations of wild cochineal (Gilreath and Smith 1988; Eisner et al. 1994) and for cultivated cochineal (Piña 1977). Such information can improve biological control of wild cochineal by means of its predators, as well as control of the predators by means of their parasitoids for cultivated cochineal.

Similar predators attack D. coccus and D. confusus, considerably reducing dye yields (Alzate 1831; Dahlgren 1963). The most common and dangerous predators are Hyperaspis sp. (Coccinelidae, Coleoptera), Chilocorus spp. (Coccineli-dae), "drum worm" (Bacca sp., Syrphidae: Diptera), Laetilia sp. (Pyralidae: Lepidoptera), Sympherobius sp. (Neuroptera), and Sapingogaster texana (Syrphidae; Piña 1977; Gilreath and Smith 1988). Homalotylus cockerella is a parasitoid of Hyperaspis trifurcata (Gilreath and Smith 1988). In Mexico, several parasitoids of the family Pteromalidae have been identified for Sapingogaster texana (Syrphidae)— Brachimeria conica, Spilochalcis flavopicta (Chalcididae), and Temelucha sp. (Ichneumonidae; Gilreath and Smith 1988) —and mites belonging to the family Piemotidae have been identified as parasitoids for Laetilia sp. In greenhouse rearings, some parasitoids (Pteromalidae) attack both cochineal and its predators (Hyperaspis sp.).

D. coccus versus Wild Cochineal

Two characteristics distinguish D. coccus from wild cottony cochineal. First, the wild insects produce a waxy, cottonlike coating, which is abundant, loose, soft, and thermally stable on the dorsal side, but compact and resistant on the ventral side, permitting firm adherence of the insect to the host platyopuntia; this coating makes the parasite resistant to wind and rain. Second, wild cochineal yields a much lower concentration of carmine colorant, from 2 to 7% by dry weight, whereas yields from D. coccus are 15 to 25%. Among other characteristics of the wild species is the ability to transmit disease to the host (Miller 1976), which in

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