Diversity of the Anisoptera & Zygoptera (Odonata: Insecta) of Swat, Pakistan

Abstract Odonates are important biological control agents for the control of insect pests and insect disease vectors of medical and veterinary importance. The present study was conducted to evaluate the odonate fauna of Swat, Pakistan from March to October 2019. A total of 200 specimens of odonates were collected from diverse habitats. The collected specimens of the order Odonata belonged to 5 families, three families of suborder Anisoptera namely Libellulidae, Gomphidae and Aeshnidae while two families of suborder Zygoptera (Chlorocyphidae and Coenagrionidae). The specimens were categorized into 12 genera and 22 species. Libellulidae was the dominant family (n = 138) accounting for 69% of the odonate fauna. Orthetrum was the dominant genus (n = 73) of suborder Anisoptera accounting for 36.5% of the odonate fauna. The least dominant genera were Anax, Paragomphus and Rhyothemis (n = 5 each) accounting each for 2.5% of the odonate fauna. In Zygoptera, the dominant genus was Ceriagrion (12.5%) and the least dominant genus was Ischnura (6%). Pantala flavescens (Fabricius, 1798) was the most abundant odonate species in the study area recorded from all surveyed habitats. Shannon Diversity Index (H) was 2.988 and Simpson Diversity Index (D) was 0.95 for the collected odonate fauna. The highest abundance of Odonata was recorded in August, September and May while no odonate species were recorded in January, February, November and December. Lotic water bodies were the most suitable habitats with abundant odonate fauna. Anax immaculifrons (Rambur, 1842) was the largest sized odonate species having a wingspan of 53.2±1.63 mm and body length of 56.3 ± 0.4 mm. The present study shows the status of odonate fauna of Swat, Pakistan in diverse habitats and seasonsonal variation throughout the year. Further work is recommended to bridge the gaps in the existing literature.


Study area
The present study was conducted at District Swat, Pakistan. Swat is located at 35.2227 0 N and 72.4258 0 E with a total area of 5337 Km 2 . Diverse habitats including running and stagnant freshwater bodies, rice fields, marshes, low and high-altitude mountainous areas were surveyed for the collection of odonate fauna. The habitats surveyed for the collection of odonate fauna are given (see Figure 1).

Sample collection
Collection of dragonflies and damselflies was made from March to October 2019 through aerial nets; the sites were sampled in sunny days between 10:00 am and 02:00 pm. Odonate abundance was less in the streams having pollutants and industrial chemical discharges compared with less polluted and unpolluted freshwater bodies.

Killing and preservation
The collected specimens were placed in killing bottles having Potassium Cyanide. After killing and rigor mortis, the specimens were properly pinned in the setting boards, labelled, and mounted in the entomological boxes. Naphthalene balls were placed in the boxes to prevent them from pests. All these activities were carried out in the Agriculture Research Institute, Takhta Band, Swat.

Identification
Identification of the specimens was done in the Entomology Laboratory, Department of Zoology, University of Malakand, Pakistan with the help of taxonomic keys and previous literature by Nair (2011), Fraser (1933 and through internet surfing. Morphological characters of the adult odonate specimens were studied with the help of Lx 400 binocular microscope.

Morphometric measurements
Wingspan and body length of the collected specimens were calculated in millimeters (mm) with the help of a ruler. Mean values of the wingspan and body length of all specimens in each species were calculated and tabulated (as shown in Table 1).

Data analysis
Data was calculated using MS Excel 2016. Shannon diversity index (H) and Simpson diversity index (D) were calculated for the odonate fauna using the formulae given in the results section. Morphometrics of the identified species were calculated and their mean values with standard deviations are tabulated in the results section.

Results
The collected specimens (n = 200) of Odonata were categorized into 22 species, belonging to 5 families. Suborder Anisoptera was represented by families Gomphidae, Libellulidae and Aeshnidae. Family Gomphidae

Introduction
Anisoptera (dragonflies) and Zygoptera (damselflies) (Odonata: Insecta) represent a diverse group of insects having 5740 described species worldwide (Johari and Jain, 2021). Odonates are beneficial insects and play an important role in pest management both as nymphs and adults (Trueman and Rowe, 2009;Ilahi et al., 2019). They are easily recognized by a long slender abdomen, large eyes, short antennae, and long membranous wings with beautifully colored bodies (Nair, 2011). The male odonates are usually brightly colored than females. Odonates tend to inhabit both lotic and lentic water bodies. They are mostly found around the fresh water, and act as biological indicators. They are good ecological indicators of the ecosystem (Johnson and Triplehorn, 2005). The presence of Odonata on water shows its pollution-free status.
Odonates are predators both in the larval stage as well as adult stage; their larvae are voracious feeders and possess large retractable labium for capturing prey. They are known to feed on mosquito larvae, protozoans and small crustaceans (Irshad, 2008) tadpoles, fish fry and even larvae of other odonates (Boyd, 2005). Adults normally feed on small flying insects like gnats, moths and noxious flies (Fraser, 1933) and act as important biocontrol agents. Odonates act as predators of mosquito larvae and play an important role in regulation of mosquito population (Knight and Larsen, 2004). Due to predatory potential against mosquito larvae, they are used in the ecofriendly control of mosquito larvae (Mitra, 2002). The nymphs of Odonata play important role in the regulation of mosquito population (Din et al., 2013) and are very sensitive to environmental pollutants (Clark and Samways, 1996). The adults mostly feed on the harmful insects, which infest orchard and forest, and maintain forest and agricultural fields (Mitra, 2002).
Inventories of target taxa provide good data. Odonates are diverse in habitats, but some species are specific to habitats which make them useful as biological indicators (Clark and Samways, 1996;Samways and Steytler, 1996). Many species of Odonata are specialists which are sensitive to changes in habitats and become extinct than generalist species (Suhonen et al., 2014). Anisoptera which includes the dragonflies are larger in size and are more resistant to disturbance, do not require riparian vegetation and found mostly in open areas to absorb the sunlight (DeMarco Junior and Resende, 2002). Urbanization is one of the major causes for the loss of odonate diversity (Willigalla and Fartmann, 2012).
The odonates fauna of Pakistan has been less investigated than their neighbor countries. Studies on Odonate fauna from some parts of Pakistan include Rafi et al. (2009, 2011, Din et al. (2013), Perveen et al. (2014), Chaudhry et al. (2016) and Fazlullah et al. (2016). The present study was aimed to evaluate the diversity of the suborders Anisoptera and Zygoptera of the order Odonata in Swat, Pakistan across diverse habitats and in different seasons of the year.
(clubtails) was represented by the common hooktails Paragomphus lineatus (Selys 1850) in which the males were medium-sized (32-37 mm long with a wingspan of 24-27 mm, yellow and black dragonflies identified by the lateral expansions of 8th and 9th abdominal segments and diagnostic hook-shaped superior anal appendages. The females were somewhat similar in size but duller in color lacking lateral expansions to abdomen. Family Libellulidae (Skimmers or perches) was the dominant family recorded from diverse habitats in the present study. The males are often brightly colored. The habitat choice varies hugely and encompasses almost all forms of wetlands including garden ponds, marshes, lakes, rivers and even seasonal rainwater puddles. Libellulidae was represented by  Morphometric parameters of all collected specimens were carried out and the values (Mean ± Standard Deviation) were tabulated (as shown in Table 1).
Suborder Zygoptera was represented by families Chlorocyphidae and Coenagrionidae. Chlorocyphidae (stream jewels) are characterized by large prominent eyes and are medium sized having projecting nose. Their wings are longer than their abdomens. Sexual dimorphism between male and female is common, males have colorful metallic patches on their wings while females have transparent wings. They mostly inhabit flowing streams. Species belonging to family Chlorocyphidae in the present study were Rhinocypha quadrimaculata and Rhinocypha bisignata (as shown in Table 1). Rhinocypha quadrimaculata (Selys, 1853) is commonly known as black emperor because of the black coloration with pinkish triangular mid thoracic patches. They are medium sized with males 25 mm long with wing length of 27 mm while females are 25 mm long with a wingspan of 31 mm. Rhinocypha bisignata (Selys, 1853) is commonly known as stream ruby. Family Coenagrionidae (marsh darts) was represented by three species, Ceriagrion coromandelianum, Ceriagrion olivaceum and Ischnura aurora. Ceriagrion coromandelianum (Fabricius, 1798) is a medium-sized damselfly having yellowish-green eyes. Thorax is green above and yellowish green on the sides with yellow abdomen. Females are more robust having dull coloration. Males are 20 mm with a wingspan of 24-26 mm. Females are 16 mm long with wingspan of 22 mm. Ceriagrion olivaceum (Laidlaw, 1914) is a medium sized damselfly having brown capped greenish eyes, thorax green in color and paler on the sides. Ischnura aurora (Brauer 1865) is also known as aurora bluetail. A small apple green damselfly having black stripes on its thorax and blue tipped yellow tail. Males are brightly colored while the females have dull coloration. The highest abundance of the odonates was recorded in August, September and May while no odonate species were detected in January, February, November and December (as shown in Table 2). Reasons for the low diversity in the specific months are the unfavorable climatic conditions which restricts the increase in populations of insect fauna. Lotic water bodies were dominated by odonates followed by lentic water bodies while the least number of odonate species was recorded in hilly areas with scarce water bodies (as shown in Table 3). A diverse fauna of Odonata was recorded in the present study as indicated by the values of Shannon Diversity Index (H = 2.988) and Simpson Diversity Index (D = 0.95) (as shown in Table 4). A total of 12 genera of odonates were recorded in the present study with Orthetrum as the highest prevalent genus having a relative abundance of 36.6% and the genera Paragompus and Rhyothemis were the least abundant species having relative abundance of 2.5% each (as shown in Table 5). Overall, 22 species of odonates were recorded in the present study from diverse habitats with Pantala flavescens (Libellulidae: Anisoptera) as the most abundant species (as shown in Table 1). Morphometrics of the collected specimens showed that Anax immaculifrons was large sized odonate species having a wingspan (53.2±1.63 mm) and body length (56.3 ± 0.4 mm) (as shown in Table 1).
Shannon diversity index (H) is given by the formula 1: Where Pi is the proportion of individuals of a given species and ln stands for natural log. In the present study, H= -(-2.988) = 2.988 Simpson diversity index (D) is calculated by the given formula 2: Where "n" is the total no of organisms of a given species while "N" is the total number of organisms of all species. In the present study, D = 1- [1966/200(200-1)] = 1-0.049 = 0.95

Discussion
The present study was conducted to evaluate the diversity of the suborders Anisoptera and Zygoptera of Total - ---2  6  42  33  18  49  46  04  ----200 the order Odonata (Insecta) of Swat, Pakistan. A total of 22 species were identified belonging to 12 genera and 5 families and 2 suborders of the Order Odonata. Suborder Anisoptera comprised 74% (n=148) while suborder Zygoptera comprised 26% (n=52) of the odonate species with family Libellulidae the largest family. This pattern conforms to the overall abundance and diversity of odonate fauna worldwide as is evident from a recent report on the odonate fauna of Brazil (Garcia Junior et al., 2021). Some of the successful traits that make family Libellulidae the dominant family in diverse habitats worldwide include their ability to efficiently control their body temperature (Corbet & May 2008), adaptation to open vegetation environments (Rodrigues & Roque 2017), survival in human dominated habitats (Damaceno et al. 2014) and a great dispersion potential The family Coenagrionidae of the suborder Zygoptera was the abundant family (n = 37) with three identified species followed by Chlorocyphidae (n = 15) with two identified species. Zygopterans are mostly habitat specific representing peculiar habitats and are not dominant in diverse habitats like Anisoptera. This property makes them less diverse and resultantly leads to less catch during various sampling techniques. The less abundance of the species of Zygoptera can be attributed to their small sizes and the resultant restrictions to habitats with less temperature fluctuations and less exposure to sunlight (Brasil et al. 2019).
Abundant species of Anisoptera were Pantala flavescens and Orthetrum pruinosum while in Zygoptera, Ceriagrion coromandelianum was the most dominant species in District Swat, Pakistan representing maximum number of specimens found in diverse habitats ranging from lotic to lentic water bodies, hilly areas, marshes, running streams, grasslands, rice lands and swampy areas. The species P. flavescens was collected almost from all surveyed habitats.
The variations among different reports are because of the different ecological, climatic and topographic conditions of the study areas along with differences in the sampling techniques. Overall, odonate fauna is diverse in habitats with fresh and unpolluted water bodies encompassing rich vegetation. The present study shows the status of odonate fauna of Swat, Pakistan with 22 species belonging to 5 families and 12 genera of the two suborders of Odonata, Anisoptera and Zygoptera. Decline in the odonate fauna compared with some of the previous reports like Chaudhry et al. (2016) and Zia et al. (2009) is indicative of the habitat degradation due to enhanced anthropogenic activities. Conservation measures are required to protect the diversity of these important biological control agents in diverse ecosystems. Further work is recommended on odonate adults as well as naiads and allied insect fauna of the study area to bridge the gaps found in the existing literature for future planning and conservation measures.