08_Sarra-1.indd UDC 595.78:582.475.2(65) EGG BATCHES PARASITISM OF PROCESSIONARY MOTH, THAUMETOPOEA PITYOCAMPA (LEPIDOPTERA, THAUMETOPOEIDAE), FROM TWO ATLAS CEDAR ECOTYPES IN ALGERIA S. Ayache1, M. El Mokhefi 2, L. Bonifácio3, G. Chakali 1 1Higher National Agronomic School, Department of Agricultural and Forest Zoology, El-Harrach, 16200 Algiers, Algeria 2National Veterinary School, Bab Ezzouar, Algiers, Algeria 3Nacional Institute for Agricultural and Veterinary researcg, Quinta do Marques, Av. Da Republica, 2780-159 Oeiras, Portugal E-mail: sarra.dz92@yahoo.com S. Ayache (https://orcid.org/0000-0002-6119-6313) Egg Batches Parasitism of Processionary Moth, Th aumetopoea pityocampa (Lepidoptera, Th aumetopoeidae), from Two Atlas Cedar Ecotypes in Algeria. Ayache, S., El Mokhefi , M., Bonifácio,  L., Chakali, G.  — In the Atlas cedar forests located on the northern massifs of the Blidean Atlas and at the eastern extension of the Saharan Atlas, 79 egg batches of processionary moth Th aumetopoea pityocampa (Denis & Schiff ermuller, 1775) were collected during the summer period from two sites: Chréa National park (46), and Ouled Yagoub forest (33). To assess the eff ect of the egg batches characteristics on the parasitism, the eggs were monitored aft er the hatching of the larvae and/ or the emergence of the parasitoids. Th e average number of eggs/batches in the Ouled Yagoub site (184 eggs) was signifi cantly higher than of the population of Chréa (151). Data analysis showed that the means comparisons of the hatched and unhatched number of eggs between the two sites were signifi cant. In the case of the population of Chréa, the egg mass was laid in the form of a cylinder on twigs of relatively small diameters while for the population of Ouled Yagoub eggs were laid in the form of plates on twigs of larger diameter, thus more exposed to parasitoids. For the two populations, three active egg parasitoids were identifi ed: Ooencyrtus pityocampae (Mercet, 1921) (Encyrtidae), Baryscapus servadeii (Domenichini, 1965) (Eulophidae), and Trichogramma embryophagum (Hartig, 1838) (Trichogrammatidae), the most dominant. Th ese parasitoids were heterogeneously distributed on the egg batches collected in the cedar’s plantation of the Chréa, but homogeneously on the egg batches collected in the Ouled Yagoub cedar forest. Th e activity and distribution of parasitoids on the egg-laying surface are infl uenced by the form on the branch chosen by the female. K e y w o r d s : processionary moth, fecundity, egg parasitoids, Cedrus atlantica. Zoodiversity, 55(3): 239–250, 2021 DOI 10.15407/zoo2021.03.239 240 S. Ayache, M. El Mokhefi , L. Bonifácio, G. Chakali Introduction Th e winter pine processionary moth, Th aumetopoea pityocampa (Denis & Schiff ermuller, 1775) is the major defoliator of pines around the Mediterranean basin (Demolin, 1969). During gradations, this pest is capable of attacking vigorous trees and deteriorates their health (Huchon & Demolin, 1971). Currently, populations of this insect attack mainly, Aleppo pine (Pinus halepensis Mill.) in the semi-arid area and Atlas cedar (Cedrus atlantica Manetti) in sub-humid elevation area stands causing considerable economic losses (Sbabdji et al., 2009). Many authors report that increasing infestation rates and the environmental damage caused by processionary moth within its recent distribution range is related to climatic changes (Battisti et al., 2005; Battisti et al., 2006; Toff olo et al., 2006; Rousselet et al., 2010). By genetic structure processionary moth is presented by two well-geographically localized clades: the pityocampa clade, identifi ed in Europe, Morocco, and south-western Algeria; and the ENA (Eastern North Africa) clade, found in the north-eastern part of Algeria, northern Tunisia, and northern Libya, in the humid, sub-humid, and semi-arid climates (Kerdelhué et al., 2009; El Mokhefi et al., 2016). In Algeria, the expansion of processionary moth was favored by the Aleppo pine (Pinus halepensis) plantations along the Saharan Atlas as part of ‘Barrage vert’, started in 1983 (Zamoum et al., 2015). With global warming, the processionary moth, which has become a study model, is developing a wider horizontal and vertical expansion across the Mediterranean area (Battisti et al., 2005). In its natural biotope, T. pityocampa is a monovoltine species, but can extend its development over two or more years, depending on the altitude, according to the intensity of the diapause and the environmental conditions (i. e. temperature and insolation) (Geri, 1983). In recent years, populations of this insect have been developing continuously and the consequences of defoliations have become worrying even on cedar stands, as noticed in the Chréa National Park (Sebti & Chakali, 2014). Reproduction takes place in summer, and the larvae develop in autumn and winter. Th e life cycle is carried out in two phases, the aerial (oviposition and larval development through fi ve stages) and the underground phase (pupation) (Huchon & Demolin, 1971). Female’s choice of egg-laying site depends on some parameters such as low-density stands and high trees at the edge of the stand (Demolin, 1969; Régolini et al., 2014). In addition, the quantity and quality of nutritional resources determine the selection of the host that off ers a better chance for good larval development, and therefore an enhanced female fertility (Devkota & Schmidt, 1990; Th ompson & Pellmyr, 1991; Tiberi et al., 1999). Also, the physical and chemical characteristics of the host plant can infl uence the selection of the egg- laying site (Renwick & Chew, 1994). Th is choice is crucial as it aff ects the insect’s population dynamics and that of its egg parasitoids, which regulate its populations’ level (Morel, 2008). Egg parasitism can be noticed on 50  % of eggs during gradations (Battisti et al., 2015). Ooencyrtus pityocampae (Hymenoptera, Encyrtidae) and Baryscapus servadeii (Hymenoptera, Eulophidae) are known as the most active parasitoids in the Mediterranean region (Avci, 2003; Mirchev et al., 2007; Bouchou & Chakali, 2014; Hezil et al., 2018). Despite various studies on the biology and ecology of this defoliator, sparely information is available on the morpho-biometry of eggs, its relation with the host, and how aff ects parasitoids’ activity. Th e main objective of the study was to assess the characteristics relating to the structure of egg batches in two natural Atlas cedar stands of Chréa and Ouled Yacoub; considering (i) twig diameter, (ii) egg batch length, (iii) number of eggs per batch, and (iv) number of parasitized eggs per batch. In addition, information on the relationship between the egg batch form and the specifi c distribution of embryonic parasitoids was discussed. From the results obtained, the relationship was found between the various environmental parameters and the choice of egg-laying sites in the analyzed ecotypes. Material and methods S t u d y s i t e s Th e sampling was carried out in 2017 in two natural Atlas cedar stands (table 1). Chréa plot is a part of the National Park that covers an area of 7.000 ha, located on the Tellian Atlas, 50 km south-west of the capital Algiers. Th e locality is under a subhumid bioclimate, with average temperatures of 5 °C in winter and 22 °C in summer, and an average annual rainfall of 700 mm. Th e locality of the Ouled Yagoub plot belongs to Chelia National Park that extends over an area of 3.000 ha on the eastern part of the Saharan Atlas, at 500 km south-east of the capital. Th is area is located in a subhumid bioclimate, characterized by average annual temperatures of 7 °C and 25 °C in winter and summer, respectively and an average annual rainfall of 550 mm. C o l l e c t i o n a n d p r e p a r a t i o n o f b i o l o g i c a l m a t e r i a l A total of 79 eggs batches were collected during the summer period (46 for the Chréa site and 33 for Ouled Yagoub). Egg batches have a cylindrical form of few centimeters in length, laid on twigs of various diameters (fi g. 1, A; B). Along a linear transect, one twig containing a batch of eggs was sampled using a lopper and individually stored in glass tubes (10 cm long and 1 cm diameter), numbered, and capped with fi ne cotton to allow air circulation. Egg batches found in thicker twigs, exceeding the tube diameter, were stored individually in transparent cups (8 cm long and 5 cm diameter) and closed with a fi ne mesh fabric. Th e material thus 241Egg Batches Parasitism of Processionary Moth, Th aumetopoea pityocampa… prepared was stored in laboratory conditions at 25 ± 2 °C temperature, and 70 ± 5 % of relative humidity. Eggs were monitored daily for hatching larvae and parasitoids emergence, over a period of 60 days. Th e meconium was used for primarily identifi cation of the parasitoid species according to the method proposed by Tsankov et al. (1996). Th e shape of meconium varies depending on the species. For O. pityocampa, it is a fl at yellow disc while that of B. servadeii is a single ball stuck on the chorion of the egg. Adult wasps were identifi ed by G. Chakali and verifi ed by B. Pintureau (UMR INRA/INSA de Lyon — Biologie Fonctionnelle) and by molecular analysis carried out by the team of Dr. Ris in Nice (Antibes). M e a s u r e m e n t s a n d e g g c o u n t i n g Th e diameter of the supporting twig and the egg batch length were measured using an electronic caliper. Protective scales were carefully removed from egg batches using adhesive tape to count the total number of eggs per batch, under a binocular magnifi er. Mean values were used to assess female fertility in the two localities. Th e egg batches were divided into three parts using a marker: upper, middle, and basal, in order to determine the parasitoids distribution pattern. Th e upper part of the egg mass considered is the location towards the top of the branch. Th ree types of eggs were determined for each batch (fi g. 1, C): 1) Non-parasitized eggs, recognizable by the rounded shape and the whitish color. Aft er completing their embryonic development, larvae hatch leaving a circular hole. 2) Empty eggs have a pure yellowish color. Th eir sterility is usually due to embryonic fall (mortality), or because the egg contains a diapausing parasite. 3) Parasitized eggs, which become blackish a T a b l e 1 . Sampling sites location Sites Geographical coordinates Cardinal position Latitude Longitude Elevation (m) Chréa (NW) 36°26´02.0˝ N 2°53´00.0˝ E 1438 Ouled Yagoub (SE) 35°19´21.0˝ N 6°37´53.0˝ E 2096 Fig. 1. Eggs batches of Th aumetopoea pityocampa: A — cylindrical form; B — egg batches in thick twigs; C — types of eggs. A B C O. pityocampae T. embryophagum Hatching larvae B. servadeii 242 S. Ayache, M. El Mokhefi , L. Bonifácio, G. Chakali few days aft er being parasitized. Th e holes left by the parasitoid aft er emergence is relatively smaller than those produced by larval hatching. Inside of the parasitized egg remains of the host insect embryo and meconium left by the parasitoid just before emergence can be found. Th e emergence of T. embryophagum is characterized by very small round exit holes (one to three per egg), compared to other parasitoids (Tsankov et al., 1996). D a t a a n a l y s i s Th e characterization of the egg-laying of T. pityocampa involves two variables groups: variables related to the moth’s fertility, and host tree variables, i. e. diameter of twigs carrying the egg batch. Linear regressions were performed to calculate the correlations and the equations which signifi cantly describe the relationships between the number of eggs and the size of the egg batches. A descriptive analysis and unidirectional analysis of variances (ANOVA), with results interpreted at the 5 % error, were carried out to assess the eff ect on the moth’s populations of the variables selected for the two surveyed sites. All analyzes were carried out using XLSTAT (Version 2016.02.28451) and STATISTICA soft ware (Statsoft Inc. 2003; version 6.0). Results and discussion A n a l y s i s o f t h e b i o l o g i c a l m a t e r i a l Th e data collected from the two study sites on the biometrics of the support branches, batch characteristics and the count of the egg’s categories are presented in table 2. All variables considered presented statistical signifi cant diff erences between sites. Th e average diameters of the twigs chosen by the females for laying eggs were signifi cantly bigger in the cedar forest of Ouled Yagoub than in Chréa, with 6.5 mm and 4.1 mm respectively. Th e number of rows laid in parallel by the females was also bigger in Ouled Yagoub but with higher variability (4 to 24 rows) when compared to Chréa (5 to 11 rows). A remarkable adaptation was noted on the females of the Ouled Yagoub site which have the ability to cling to thick twigs to lay the eggs and easily maintain themselves on thicker branches than those from the Chréa area. Th is variability observed between the studied populations is associated of environmental factors, and the ecotype of each population. Quantitatively, the female fertility estimated from the total number of eggs per batch was signifi cantly higher in the Ouled Yagoub site (184) compared to the Chréa population (151). Considerably greater average hatching of 94 eggs/batch was obtained from the biological material collected in Chréa, despite greater fertility of the population T a b l e 2 . Descriptive statistics related to twigs, batches, and eggs categories, and the corresponding statistical signifi cance between sites Sites Chréa Ouled Yagoub Sample sizes 46 33 Descriptives mean ± SD (min–max) mean ± SD (min–max) Twig diameter, mm*** 4.1 ± 1.1 2.2–6.6 6.5 ± 3.4 2.5–13.7 Batch length, mm* 23.8 ± 4.8 12.9–34.1 27.7 ± 7.6 20–59.1 Total eggs*** 151 ± 26 84–235 184 ± 55 103–335 Rows/batch*** 7 ± 2 5–11 11 ± 5 4–24 Hatched eggs* 94 ± 52 0–206 62 ± 61 0–216 Non hatched eggs*** 47 ± 39 0–157 111 ± 75 5–310 Parasitized eggs* 10 ± 14 0–70 11 ± 10 0–39 * p < 0.05 ; ** p < 0.01 ; *** p < 0.001 243Egg Batches Parasitism of Processionary Moth, Th aumetopoea pityocampa… of Ouled Yagoub, where the mean number of unhatched eggs was more than twice the number of unhatched eggs in Chréa, with 111 and 47 respectively. Th is could be explained by the collection of egg-batches at altitude, which oft en results in non-fertile eggs as reported by Démolin (1969). Likewise, the very oft en severe conditions at altitude, where minimum temperatures can reach –10 °C, could have a negative infl uence on embryos. In the case of the Chréa population, the laying was in the form of a cylinder while for the Ouled Yagoub population, the egg batches were rather fl at, therefore more exposed to the parasitoids, with signifi cant impact. C o r r e l a t i o n b e t w e e n b a t c h l e n g t h a n d t h e t o t a l n u m b e r o f e g g s A high positive correlation between the batch length and the number of eggs was evaluated for the population at Chréa (R² = 0.7432), while for the population of Ouled Yagoub, the correlation was also positive yet relatively less signifi cant (R² = 0.2214) (fi g. 2). Despite the higher fertility of the population of Ouled Yagoub, the arrangement of the eggs on the twigs is not as appropriate as is Chréa population. B A Fig. 2. Relationship between batch length and the number of eggs in Chréa (A) and Ouled Yagoub (B). Ta b l e 3 . Importance of the embryonic parasitoids of Th aumetopoea pityocampa obtained in the egg batches collected in the study sites Sites Parasitoïds Chréa Sample sizes (46) Ouled Yagoub Sample sizes (33) mean ± SD (min–max) relative abondance, % mean ±SD (min–max) relative abondance, % Ooencyrtus pityocampae  2 ± 2 (1–18) 11 6 ± 4 (2–21) 17 Baryscapus servadeii 5 ± 5 (2–58) 28 3 ± 3 (2–22) 29 Trichogramma embryophagum 50 ± 43 (9–129) 61 14 ± 15 (11–64) 54 244 S. Ayache, M. El Mokhefi , L. Bonifácio, G. Chakali C o r r e l a t i o n b e t w e e n t h e t w i g d i a m e t e r a n d t h e n u m b e r o f r o w s o f e g g s / b a t c h Th e relationship between the size of the branches chosen by the females and the number of ordered rows laid is illustrated in fi gure 3, and for both sites, the number of egg rows is highly correlated to the median values of the supporting branches, revealing the female’s strategy in the laying and arrangement of eggs in relation to the host characteristics. E m e r g e n c e a n d a c t i v i t y o f p a r a s i t o i d s In the both studied sites, three species of embryonic parasitoids were identifi ed from the biological material analyzed. Th ese are two solitary Chalcidoidea: Baryscapus servadeii (Domenichini) (Hymenoptera, Eulophidae) and Ooencyrtus pityocampae (Mercet) (Hymenoptera, Encyrtidae). Th e third species noted is Trichogramma embryophagum (Hartig) (Hymenoptera,Trichogrammatidae). Fig. 3. Distribution of the number of egg rows in relation to the twig diameter in Chréa (A), and Ouled Yagoub (B). twig diameter (mm) : F(3;42) = 168,1487; p = 0,0001 Median = -0,7223+0,7031*x R²= 0,9813 Median 25%-75% Non- atypical extent 4 6 8 9 11 Number of raws/ batch 2 3 3 4 4 5 5 6 6 7 7 tw ig d ia m et er (m m ) twig diameter (mm) : F(3;29) = 154,2128; p = 0,0001 Median = -0,3677+0,5894*x R²= 0,9561 Median 25%-75% Non-atypical extent 4 9 14 18 23 Number of raws/ batch 2 4 6 8 10 12 14 16 tw ig d ia m et er (m m ) A B 245Egg Batches Parasitism of Processionary Moth, Th aumetopoea pityocampa… For both processionary moth populations studied, T. embryophagum remains the predominate parasitoid, not only several adults emerged from the same exit hole but also some eggs showed two exit holes (table 3). Regarding the seasonality of the parasitoid species, the individuals of B. servadeii had an early emergence than the species O. pityocampa and T. embryophagum. D i s t r i b u t i o n o f p a r a s i t o i d s o n t h e e g g - b a t c h s u r f a c e Th e three listed parasitoids distributed heterogeneously on the egg batches collected in the Chréa cedar plantation, while a more homogeneous parasitoids distribution was observed on the eggs from Ouled Yagoub cedars. Th e activity of parasitoids on the batch surface is infl uenced by its form since egg batches on thicker branches usually have a fl at shape, more exposed and easier for the parasitoids action (fi g. 4). H i e r a r c h i c a l c l a s s i f i c a t i o n o f t h e v a r i a b l e s c o n s i d e r e d Th e aggregation distance as a function of consecutive steps shows the similarity of neighboring variables, number of rows/batches, diameter of twigs (fi g. 5). Th e number of parasitized and hatched eggs is closely related to the morphological characteristics of eggs. Th e more the batch is fl at. Th e variability of the parameters considered is closely related to the sites prospected. Th e egg-laying behavior of the processionary moth females is dependent on several en- vironmental variables and reveals higher fertility in the cedar forest. Th e winter procession- ary moth females have the ability to detect favorable biotopes for the release of their eggs where their progeny would have enough food for their development. It is recognized that females of T. pityocampa during their cycle lay their eggs in a single sequence. Th e num- ber of eggs per batch corresponds to the fertility of a female as described by Mirchev and Tsankov (2005), Battisti and al. (2015). Data analysis collected on the fertility of females on the Atlas cedar confi rmed the correlation mentioned by Özkazans (1987) who noted that the fertility of females increases with altitude. Th e studies carried out by Parker and Begon (1986), Freese and Zwolfer (1996), Tiberi et al. (1999) showed that the quality and quantity of resources available in the host plant are determinant ecological factors that infl uence the eggs productivity of T. pityocampa. Demolin (1969) noted that the fl uctuation of the population is related to various factors, particularly climate, altitude, food, and the antago- nists. Th is result shows that the site choice is a part of a strategy evolutionary adopted by the female for the protection of its progeny. Whatever the diameter of the branch, fertility is more substantial at altitude. Tilman (1980) noted that the female chooses the site for lay- ing eggs that can maximize the survival of its off spring due to enough amount of resources available. Fig. 4. Distribution of parasitoids on the egg-batch surface. 246 S. Ayache, M. El Mokhefi , L. Bonifácio, G. Chakali Th e variability in the choice of the twig diameters can be explained by the haplo- types’ diversity of the species in its biotope. Both populations considered are of ENA clade (Kerdelhué et al., 2015). According to the mitochondrial haplotypic network of ENA clade, the Chréa population contained essentially one haplotype (E3), thus than a limited set of 3 haplotypes (E1- E4- E8). In contrast, the population of Ouled Yagoub had one major haplotype (E1), and two haplotypes with low frequencies (E9- E8) (El-Mokhfi et al., 2016). Th e females which evolve in the cedar forest of Ouled Yagoub, have the particularity to seek more the lower part of the relatively thicker branches to carry out their fl at-shaped egg-laying, in order to protect their off spring from severe winter conditions, particularly during snowfall, which oft en lasts two months. This investigation reports the importance of fertility and the choice of twigs by females to lay their eggs along an altitudinal gradient in two natural ecotypes of the Atlas cedar, Cedrus atlantica. Likewise, in the strategy of parasitoids, the shape of the egg-batch on the twig has a decisive role in the successful establishment, this particu- larity may have a direct regulating effect on the proliferation of processionary moth populations (Biliotti, 1958; Battisti, 1989; Tsankov еt al., 1999; Mirchev et al., 2012; Mirchev et al., 2015). Halperin (1990) mentioned that the survival of polyphagous parasitoids such as O. pityocampae does not require synchronization between their emergence and the avail- ability of unhatched eggs of the processionary caterpillar. In contrast, a relay synchroniza- tion is necessary for B. servadeii because this parasitoid is endowed with specifi city towards the species of processionary moths in their range of distribution. For the Ouled Yagoub population, the two generalist parasitoids O. pityocampae and B. servadeii showed comparable frequencies. Th is suggests that the activity to be detected and the ease of parasitism of eggs by these polyphagous parasitoids is related to the availability of fl at-form egg-batches on the twigs. Mirchev et al. (2015) showed that the action of polyphagous parasitoids encompasses a wide host range and their presence Dendrogram of 7 Variables 0 100 200 300 400 500 600 700 Aggregation distance Number of eggs/ batch Length of batch Number of parasitized eggs/ batch Number of raws/ batch twig diameter (mm) Number of hatched eggs / batch Sites Fig. 5. Hierarchical classifi cation of the variables considered. 247Egg Batches Parasitism of Processionary Moth, Th aumetopoea pityocampa… in a specifi c biotope is accidental. A diff erent antagonism between the parasitoids was observed concerning their capacities to parasitize the eggs of the processionary moth in the prospected sites. Interspecifi c competition is determined by various ecological factors related to the entomological diversity which ensures the availability of alternative hosts. Mirchev and Tsankov (2005) noted that B. servadeii searches for processionary eggs at the laying time, whereas for O. pityocampa this period is speedy. In this regard, Halperin (1990) confi rmed the idea that the phenology of O. pityocampae, unlike that of B. servadeii, is not synchronized with of T. pityocampa. A comparable specifi c diversity of embryonic parasitoids has been noted in various species of the genus Th aumetopoea such as T. bonjeani in Algeria (Rahim et al., 2016), and T. pinivora in Spain (Battisti et al., 2015). An absence of B. servadeii in T. ispartaensis eggs has been noted in Turkey (Avcı, 2003). Other species of parasitoids belonging to the superfamily Chalcidoidea were recorded in low numbers on T. pityocampa eggs by various authors. Mirchev and Tsankov (2005) in the pine forests of Greece, Tiberi et al. (2015) in the pine forests of Tuscany in Italy identifi ed the species of Baryscapus transversalis, Anastatus bifasciatus, and Pediobius bruchicida. Also, the species Ooencyrtus telenomicida was noted on egg-batches collected in the pine forests in southern Italy (Tiberi, 1990). In the cedar plantations surveyed, the period of emergence of O. pityocampa and B. servadeii was synchronized with the period of oviposition of T. pityocampa in July–August. Th is is comparable with the study conducted by Zamoum et al. (2015) in the Aleppo pine forests of the sub-Saharan region in Algeria. Arnaldo and Torres (2006) in the pine forests of northern Portugal reported that the two above-mentioned parasitoids emerge in two periods, the fi rst in the fall of the same year during the egg-laying period, and the second in the spring of the year following a winter diapause. Th is explains the number of eggs quantifi ed with diapausing parasitoids in the biological material analyzed. Th e distribution of parasitized eggs is an indicator of their acclimatization to this host. Th e various parts of the egg-batches are searched indiscriminately by B. servadeii from the Chréa site, which expresses the adaptability of the species. Masutti (1964) noted that this parasitoid had the ability to slip between the protective scales to reach the eggs. Likewise, Biliotti (1958) considered that the presence of scales is a protective barrier for encyrtids, whereas they do not present an obstacle for eulophids. It is common for the eggs at both ends of the batch to be partially covered by scales and this can facilitate the action of the parasitoids O. pityocampa and T. embryophagum. In this regard, it should be noted that there are reports related to the distribution of eggs parasitized by the various antagonist species. Kitt and Schmidt (1993) found that O. pityocampa mainly seeks the apical part of the egg-batch, while B. servadeii prefers the basal part, but the results obtained by Mirchev et al. (2012) showed that the upper parts were the most sought aft er by parasitoids. A homogeneity in the distribution of embryonic parasitoids was noted in the biological material from the Ouled Yagoub area. Th e shape of the egg-batch and the architecture of the protective scales has an essential role in the distribution of parasitoids. Th ese results are reported by Arnaldo and Torres (2006) who noted that the egg-batch structure of the pine processionary moth and the associated parasitoid species are infl uenced by the morphology of the spawning supports of the various potential hosts of the pine processionary moth. Th is is valid for the cedar twigs, particularly for the Ouled Yagoub site. Morphobiometric data on the protective scales could further confi rm the choice and distribution of parasitoids on the egg-batch surface. Th e variability of fecundity and the eff ect of the twig’s diameter on the selection by the laying females between the populations of the processionary T. pityocampa in the prospected areas are under the aegis of several factors including environmental factors, and probably on the haplotypic diversity of the species within its biotope. Females have diff erent physiological and adaptive capacities for the development of their respective eggs 248 S. Ayache, M. El Mokhefi , L. Bonifácio, G. Chakali and choose sites that can maximize the larval survival of their off spring through the amount and the quality of available resources. Abbreviations ENA clade: Eastern North Africa clade; NW: North West; SE: South East. References Arnaldo, P. S., Torres, L. M. 2006. Eff ect of diff erent hosts on Th aumetopoea pityocampa populations in Northeast Portugal. 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