Like other coccinellids, the postembryonic stages of R. lophanthae consist of four larval instars, prepupa and pupal stages. A detailed morphological description of its eggs, larvae and adult male and female has been illustrated by many authors (Smirnoff 1950; DeBach 1964; Ricci 1983; McNamara and Humble 1991; Stathas 2001b; Stathas et al. 2002; Gutierrez and Pizzamiglio 2007). The life cycle begins with fertile eggs laid by the mated female. Adult females lay eggs under the scales of diaspidids, especially under the carapace of dead scales or near live prey (Stathas et al. 2002). The eggs have an elliptical shape with a narrowed front edge. The egg color depends on the prey the female feeds on. Females fed on A. nerii Bouché (Diaspididae: Hemiptera) lay yellow eggs, whereas those preying upon Parlatoria pergandii Comstock lay red rose-colored eggs (Stathas 2001b). Branco et al. (2017) reported the length and width of eggs from adult females fed on C. dictyospermi Morgan (Diaspididae: Hemiptera) to be 0.514 and 0.254 mm, while the egg volume was 0.018 mm³. Ricci (1983) described the chaetotaxy of the head, thorax and abdomen of 4^th instar larva and pupa. Larvae possess a strongly sclerotized head, less sclerotized thoracic segments (including legs) and a slightly sclerotized abdomen. Initially, the color of the body is dark, ranging from green to gray. The head capsule varies with the larval age, and it is dimensions were reported as 0.22, 0.29, 0. 42 and 0.55 mm for the 1^st, 2^nd, 3^rd and 4^th larval instars, respectively. However, in all larval instars the length of tibia I is shorter than that tibia II and tibia III. Two internal and two external parallel longitudinal lines of setae and microtrichia are present on the dorsal side. A high number of setae are observed on the lateral side, which increases from 2^nd to 4^th larval instars. Both larval instars and pupae of R. lophanthae had the same number and distribution of spiracles. Pupal color depends on the body color of its scale prey. The pupa is entirely covered by setae (Stathas 2001b). The shape of the pupa is broad and oval with a narrow end. The shape of the adult is quite elliptical.

The mature adult of R. lophanthae is a small-sized coccinellid. The mature adult female measures about 2.5 mm in length and 1.8 mm in width, while the adult male is 2.4 mm in length and 1.74 mm in width, with a reddish-brown head. Both sexes have 9 antennomeres; antennae consisting of meagre morphological studies. The whole surface of the thorax and elytra are covered by setae. The adult female is 2.5 mm and 1.8 mm in length and width, respectively. The adult male is 2.4 mm in length and 1.74 mm in width with a reddish-brown head. The whole surface of the thorax and elytra are covered by setae. The tarsus of the legs is 3 segmented. The testes consist of 10 follicles, and the ovaries are made of 10 ovarioles. The two sexes can be identified by the last abdominal segments. The outline of the 5^th ventrite (7^th sternite = 5^th visible ventrite) is useful to distinguish the sexes. In females, it is arched and in males it has a recess like wide U shape. R. lophanthae has a reddish head with a grayish back underside (Stathas et al. 2002). The color of adult parts varies in different geographical regions. The head, palpi, antennae, legs and ventral surface in Canadian populations range from yellow to brownish yellow, and elytra brown to dark brown with slight metallic lustre. The ventral surface and legs with whitish-golden pubescence; dorsal surface with dense, decumbent, whitish-golden pubescence intermixed with long, erect and brownish setae (McNamara and Humble 1991).

In the mass production of the ladybird, it will be beneficial if the sex ratio is female-biased, as females will help in increasing the numbers (Kundoo and Khan 2017). Female-biased ratio has also been reported in other scale insect predators, i.e., Chilocorus nigritus (Coleoptera: Coccinellidae) (Omkar and Pervez 2003). To our knowledge, there is no available data on the male killing phenomenon among the R. lophanthae population.

Embryonic (egg) and post embryonic stages (larvae)of R. lophanthae can develop and survive to adulthood at various temperature regimes ranging from 15 to 30 °C (Stathas et al. 2002; Nar et al. 2009; Abu Alloush 2019). The highest mortality rate (8.5%) occurs during the egg stage at 20 °C, whereas total mortality from 1^st larval instar to the pupa ranged from 41.65% at 25 °C to 65.2% at 35 °C (Nar et al. 2009). No mortality was observed in 4^th larval instars at 25 and 30 °C (Nar et al. 2009). Stathas et al. (2002) reported that the mortality rate of the pupal stage fed on C. aonidium was 3.3%, at 15 °C, whereas there was no mortality during the egg, 3^rd, 4^th larval and pupal stages at 25 °C. Senal et al. (2017) studied the effect of cold storage on the adult stage and found that adults kept at 4 °C for 30 and 40 days died. Most studies have investigated that the survival rate in R. lophanthae is mainly associated with prey species, host plant and temperature. The moderate Eu-Mediterranean climate allows this predator to survive and remain active throughout the year, during moderate and high winter seasons. According to Kingsolver et al. (2013) species at mid-latitudes will be highly susceptible to heat stress due to temperature variation caused by climate change. There is no available empirical data on the effect of extreme summer temperatures on the mortality rate of R. lophanthae and, therefore, it is not possible to predict the impact of heat stress on the performance of the predator. However, the mortality among the field generations was reported in Greece. Of the six field generations developed in Greece for two consecutive years, the mortality was reported only in the 5^th generation, ranging from 47% and 63% in 1994 and 1995, respectively (Stathas 2000b). The high mortality rate may be associated with the temperature differences (degree-days) during the season.

Predatory attributes of R. lophanthae have been reported by many authors. Its key attributes include good prey selectivity, long adult longevity, high fecundity, lack of diapause, high mobility, rapid development (five to eight generations in a year), lack of parasitism (Smirnoff 1950; Stathas 2000b; Vives 2002; Gutierrez and Pizzamiglio 2007; Flores and Carlson 2009), and resistance to low temperature, especially in the immature stages (Stathas 2000b). Rhyzobius lophanthae exhibits the type III functional response (Gutierrez and Pizzamiglio 2007), resulting in high mortality of its prey. Both, larval and adults predate the scale insects (Stathas 2000a). Voracity and fecundity, and the effect of temperature on both parameters were widely investigated (Stathas 2000a, 2000b; Kayahan et al. 2021). Both daily and total consumption increase with rising temperatures. As the immature stages continue their development, daily and total consumption also increases. Significant differences in voracity between males and females have been reported. The 1^st, 2^nd, 3^rd and 4^th instar larvae of R. lophanthae consume 1.2, 2.7, 7.5 and 24.6 adult females of A. nerii at 25 °C, respectively. The total consumption by all instars was 36 adult females of A. nerii at 25 °C, newly hatched R. lophanthae larvae consumed 100 third instar scales to reach maturity (Thorson 2009). A female consumes 100–125 large scales of A. nerii and adult male consumes half of this amount (Flores and Carlson 2009). Stathas (2000a) estimated that average prey consumption by male and female during their lifetime is 390.6 and 672.3 of A. yasumatsui, respectively. The predation rate by larval instars was 58.4 individuals, while that of adult males and females were 121.9 and 175.8 adults of A. yasumatsui, respectively. Thorson (2009) pointed out that daily and total consumption by adult females (281 adult scale insects) was greater and significantly higher than that of adult males (194 adults) when fed on A. yasumatsui at 24 °C. However, prey consumption is dependent on the prey specie, and influence by factors such as prey mobility, nutritional status, the suitability of the prey for the predator’s growth and reproduction, prey size and the host plant of the prey (Uygun and Elekciouglu 1998; Kundoo and Khan 2017). Honda and Luck (1995) compared the morphological characteristics of the scale covers and bodies of two scale species of California red scale A. aurantii (Maskell) and oleander scale, A. nerii (Bouche) with respect to predation by R. lophanthae. A higher percentage of R. lophanthae larvae survived when they were fed on 2^nd and 3^rd instars of A. aurantii and all stages of A. nerii than when they were fed ovipositing A. aurantii. Adults R. lophanthae took longer to consume 3^rd-instar of A. aurantii than 3^rd-instar of A. nerii and were unable to prey upon the scale body of ovipositing A. aurantii. Moreover, 32 out of 40 adult R. lophanthae emerged from the larvae fed on the gravid females of A. nerii, and only one out of 40 adult emerged when the predator fed on gravid females of A. aurantia. The morphological traits of both the predator and prey influence the predators’ ability to exploit them, and the prey stages vary in the nutritional value they provide. It is evident that that adult beetles require extended periods to penetrate the hard cover. The opposite was reported for the adults of C. nigritus, which preferred A. aurantii to A. nerii (Omkar and Pervez 2003). However, few studies have been investigate the effect of sclae insects’ morphology on the survivorship, and other biological parameters of the coccinellid predators. It is possible that the differences between the armored and soft-bodied covers play a vital role in the predation capabilities of R. lophanthae.

Fecundity and reproductive attributes of R. lophanthae have been studied under various prey species and temperature regimes (Stathas 2000b; Nar at al. 2009). Cividanes and Gutierrez (1996) developed a model for the growth, development, and reproductive attributes of R. lophanthae feeding on A. nerii. When provide with unlimited food, the relation between mass at time t+1 (in days at 25 °C) showed a growth rate of 8.7% per mg of larvae per day. An adult female produces 20 eggs per day after consuming an average of 8.5 scales per day. Stathas (2000a) reported a maximum daily oviposition of 18–25 eggs, with an average of 10 eggs per day. The daily oviposition fluctuated with the reproductive age of the females and the peak of daily oviposition during the first 20–30 days with an average of 18–25 eggs (Stathas 2000a; Vives 2002). The lifetime fecundity of R. lophanthae females is strongly influenced by different prey species and abiotic conditions. The lifetime fecundity ranged from 222 to 1152 eggs per female with an average of 633 eggs at 25 °C. Most of the eggs are laid under the scale cover of A. nerii in groups of one to five (Stathas 2000a). Adult females invest around nine times their body mass in the production and oviposition. fecundity over yielded 600 eggs, which is the highest for this coccinellid on A. nerii at 25 °C (Rosen 1990; Stathas 2000a, b). The fecundity of other scale predator C. nigritus on various prey species ranged from 90 to 370 eggs (Pervez and Omkar 2003).

The pre-oviposition period of R. lophanthae was 5 and 3.8 days at 25 and 30 °C, respectively (Stathas 2000b). Temperature regime significantly influenced the pre-oviposition, oviposition and post-oviposition periods along with the fecundity (Stathas 2000b). The oviposition period lasted for 12 days at 25 °C when the female was fed on A. aurantii (Sismek et al. 2016) and up to two months at 25 °C when fed on C. dictyospermi (Branco et al. 2017). Rhyzobius lophanthae is a potential predator of scales based on voracity and reproductive attributes, and both the parameters are affected by environmental conditions, especially the temperature and the prey species.

Prey species and temperature significantly influence the growth rate and developmental time of immature stages as well as adult longevity. The effects of temperature and prey species on life history, adult longevity, and life tables have been widely studied (Stathas 2000b; Stathas 2001b; Stathas et al. 2002, 2019; Nar et al. 2009; Simsek et al. 2016; Branco et al. 2017). As temperature increased (15–30 °C), the developmental durations of embryonic and immature stages, as well as adult longevity, decreased significantly. This trend was also reported in other coccidophagous ladybirds, such as C. bipustulatus (Eliopoulos et al. 2010; Karatay and Karaca 2013). The oleander scale A. nerii was the most suitable prey for the development of this predator as compared to other prey species. The developmental durations of immature stages were 21. 1 and 20.8 days at 25 and 35 °C, respectively (Stathas 2000b; Nar et al. 2009). The life cycle from egg to oviposition lasted for 78.7, and 23.9 days at 15 and 30 °C, respectively (Stathas 2000b). Stathas (2001b) reported that the developmental time from egg to adult stage lasted for 27.1 days when fed on A. nerii and 48.2 days when fed on A. aurantii. The low temperature threshold for immature stages ranged from 7.6 to 9.3 °C, while the thermal constant for the development of R. lophanthae, from egg to adult, was 443.5 degree-days (Stathas et al. 2002). Rhyzobius lophanthae displays high ability to survive at low temperatures ranging from 4 up to 12 °C (Senal et al. 2017).

The average adult longevity varied with temperature, prey species and availability, sex, and the mating status of females. Nar et al. (2009) reported that the lifespans of adult males and females were 43.1 and 53.2 days, respectively, at 25 °C. Rathee and Ram (2018) suggested two advantages for the storage of natural enemies at low temperatures; (i) cold-stored individuals can be quickly release during spring pest outbreaks, and (ii) tolerance to cold storage is a highly plastic trait, influenced by a range of abiotic and biotic factors during and after cold exposure. Therefore, further studies on the cold storage of R. lophanthae are recommended, including evaluation the performance of cold-stored individuals under field conditions.

Life tables are important analytical tools, generating simple but informative statistics based on the most comprehensive description of the survivorship, development, and reproduction of a population (Ali and Rizvi 2010). Understanding the life tables of both the predator and the prey is essential for the mass rearing and effective application of natural enemies to biocontrol systems (Yu et al. 2005; Kontodimas et al. 2008). Several studies have investigated the life table parameters of R. lophanthae (Stathas et al. 2005; Nar et al. 2009; and Simsek et al. 2017). The findings indicate that the prey species influence these parameters. For example, Simsek et al. (2017) examined the life tables of R. lophanthae fed on three species of scale insects. The intrinsic rate of increase for R. lophanthae fed on A. nerii, C. dictiyospermi and A. aurentii were 0.120, 0.061 and 0.041 females/female/day, respectively, while the net production rates (R0) were 36.027, 12.250 and 6.600 females/female/generation, respectively. Additionally, the total production rate (GRR) was 125.542, 65.111 and 41.369, respectively. The study conducted by Stathas et al. (2005) generated similar results reported to those by by Simsek et al. (2017), whereas the study by Nar et al. (2009) reported different findings.

Smith and Cave (2006) evaluated three concentrations of six pesticides against R. lophanthae using a coated glass vial bioassay. Mortality rate recorded 100% at all tested concentrations of methidathion, dimethoate, and malathion. Insecticidal soap, fish oils, and imidacloprid were less toxic, causing 43% mortality of R. lophanthae with insecticidal soap, 63% with imidacloprid and 46% with fish oil. The mortality rate increased with increasing pesticide concentration. Boyero et al. (2005) tested the effects of some insecticides and acaricides against citrus pests on the adult R. lophanthae. Laboratory tests were conducted to assess the toxicity of tetradifon with dicofol, chlorpyrifos, methidathion, malathion, and Spinosad as baits. Tetradifon with dicofol and spinosad proved to be harmless, while methidathion and malathion with lure were harmful. Quesada and Sadof (2020) reported the effects residues of four insecticides: Pyriproxyfen, Spiromesifen, Spirotetramat and Bifenthrin and one horticultural oil on R. lophanthae. Residues of Bifenthrin caused mortality of 98% and 79% in adults of R. lophanthae, respectively. The effects of the other three insecticides were minimal. Based on predator mortality, Bifenthrin was harmful (>75% mortality) and Pyriproxyfen, Spiromesifen, Spirotetramat and horticultural oil were harmless (<25%). Palma-Onetto et al. (2021) compared the lethal and sublethal effects of seven organic and synthetic pesticides on this predator. Overall, the impact of pesticides on R. lophanthae have been understudied, and conducting such research, particularly in regions inhabiting the predator.

On the other hand, Kaspi et al. (2019) evaluated the toxicity of six acaricides (abamectin, spirodiclofen, fenbutatin oxide, summer oil, and two sulfur formulations) in citrus orchards on the mortality of R. lophanthae. They reported that pesticide abamectin, combined with summer oil, was highly toxic to R. lophanthae larvae and adults. whereas pesticides fenbutatin oxide, spirodiclofen, summer oil, and two sulfur formulations were found to be harmless to R. lophanthae larvae and adults. High concentrations of sulfur solutions had no influence. Based on these findings, all tested pesticides, except abamectin, are harmless and could be compatible with R. lophanthae.

Research on predation attributes indicate that R. lophanthae is an effective biocontrol agent against Diaspidids (Stathas et al. 2002). Its performance against armored scales attacking economic fruit, forest trees, and ornamental plants, under laboratory, semi-field and open-field conditions, has been reported (Greathead 1973; Hodek 1973; Rosen and DeBack 1978; Rosen 1990; Honda and Luck 1995; Stathas 2000b, 2001a, b; Stathas et al. 2002, 2005; Flores and Carlson 2009; Nar et al. 2009; Simsek et al. 2017; Abu Alloush 2019; Quesada and Sadof 2020; Sanchez et al. 2021), including in tropical and sub-tropical regions (Greathead 1973). The species has been introduced in classical biocontrol programs (Hodek 1973) and has been successfully used in greenhouses to control scale insects (Van Lenteren et al. 2020). Furthermore, R. lophanthae has also demonstrated its capability to suppress populations of soft scale insects.

This species, native to Queensland, Australia (Tomaszewska 2010) was first introduced in Europe (Italy) in 1908 and imported to Portugal in the 1930’s and 1980’s (Roy and Migeon 2010). It was successfully introduced into California from New South Wales in 1889 and 1894 to control purple scale Lepidosaphes beckii Newman in citrus (Rosen and DeBach 1978). After becoming established, it became a common predator, extending its geographical range to other citrus growing regions of United States. It was introduced into Chile in 1931 to control A. aurantii (Rojas 2005; Amouroux et al. 2019). Later, R. lophanthae was imported, mass-reared and released to control various citrus pest populations of scale insects (i.e., Aspidiotus destructor Signoret, Saissetia oleae Bern, A. nerii Bouché) in the USA, South Africa, Spain, Greece and Chile (Viljoen et al. 1986; Honda and Luck 1995; Stathas 2000b; Vives 2002; Mellado 2011). It is considered as one of the main predators in citrus orchards to control C. dictyospermi in Morocco, Algeria, Bermuda, Tunisia, Georgia, Cyprus, Australia, Argentina, Portugal, and Tanzania (Smirnoff 1950; Greathead 1973; Gordon 1985; Honda and Luck 1995; Stathas 2000b; Soares et al. 2006); Carulaspis juniper (Bouché) in Italy (Greathead 1973; Honda and Luck 1995; Thorson 2009); Aulacaspis tegalensis (Zahntner) in East Africa and Turkey (Smirnoff 1950; Rubstov 1952; Greathead 1973; Ricci 1983; Katundu and Ramadhani 1988; Erler and Tunç 2001) and A. yasumatsui in Guam in 2004 (Marler and Terry 2011; Marler and Marler 2018). Recently, it was associated with C. aonidum infesting the citrus and avocado trees in Morrocco (Smaili et al. 2024). Successful control of various scale insects in the subfamily Diaspidinae has been attributed to the introduction of adults and immature stages of R. lophanthae into Italy, the Black Sea coast of Ukraine, and North Africa (Yakhontov 1960; Yu et al. 2005; Michaud 2011). It has also been recorded in the coccinellid fauna in Azerbaijan (Snegovaya and Khormizi 2022) and Switzerland (Sanchez et al. 2021). It was repeatedly released against scale pests in the palm grove of Spainsh coastal region (Vives et al. 2008). Inundative application of this ladybird was recommended as part of integrated control programs against C. dictyospermi, A. nerii, P. pergandii, L. beckii Newman and L. aphesgloverii Packard, in citrus orchards across the Mediterranean area (Vives 2002). Rhyzobius lophanthae is a predator of soft scale insects in Egypt, and attacks the red date scale insect, Phoenicococcus marlatti Cockerell (Phoenicococcidae) (Abd-Rabou et al. 2012). It was successfully employed to control the black scale, S. oleae (Bern), in California (Greathead 1973).

This species is an important predator of citrus scale insects in both the United States and Australia, although it is less effective against heavily armored species, which are more resistance during later growth stages (Honda and Luck 1995). However, it has failed to control A. aurantii, as it prefers mature female stages of the scale (Honda and Luck 1995; Marler 2012). Little information is available about the field release and release rate of R. lophanthae. Dalstein et al. (2016) pointed out that the release of commercial R. lophanthae stages in France was considered efficient against white peach scale on black current, Pseudaulacaspis pentagona and Targionito zetti (Hemiptera, Diaspididae). Guignebault (2018) suggested that the density for effective biocontrol should be 10,000/ individuals per hectare per year, with two releases of 5,000 per hectare each crop season. Two US companies, namely Gardening Zone and IPM of Alaska, recommended this predator to be augmentatively released into cycads to facilitate control of A. yasumatsui. These companies recommend releasing 20–40 beetles per infested plant (Thorson 2009). Thus R. lophanthae has been successfully introduced and established in new locations to suppress the diaspidid scale insects. However, no information is available for its mass multiplication and cost-effective medium. Further studies on the impact of climate change, genetic diversity, and the identification of both local and well-adapted strains could be useful for biocontrol programs and may provide new insights on this species.

However, two concerns may emerge with the use of R. lophanthae as a biocontrol agent. Firstly, although no study reports negative effect of this predator on native species in the regions where it was introduced, the fact is non-native species may negatively interact with local species (Matošević and Živković 2013; Honek et al. 2017), and secondly, its larvae prey upon pupae of an aphelinid ectoparasitoid, Aphytis melinusas (Sorribas and Garcia-Marí 2010).