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Biology, Behaviour and Biocontrol Efficiency of a Reduviid Predator,Sycanus reclinatus Dohrn (Heteroptera: Reduviidae) from Southern India

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Page 1. Mitt. Zool. Mus. Berl. 68 (1992) 1, 143-156 8. 5. 1992 Biology, Behaviour and Biocontrol Efficiency of a Reduviid Predator, Sycanus reclinatus Dohrn (Heteroptera: Reduviidae) from Southern India S. J. VENNISON and DP AMBROSE With 12 figures
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  Mitt. Zool. Mus. Berl. 68 (1992) 1, 143-156 8. 5. 1992 Biology, Behaviour and Biocontrol Efficiency of a Reduviid Predator, Sycanus reclinatus Dohrn Heteroptera: Reduviidae) from Southern India S. J. VENNISON nd D. P. AMBROSE With 12 figures Abstract. Sycanus reclinatus DOHRN reduviid predator, inhabits tropical evergreen forests of southern India. Females lay clusters of brown coloured eggs 22 d after emergence. The eggs hatch in 14 to 23 d and the pale-ochraceous nymphs turn into deep-ochraceous within 1 h. Total stadia1 period from I instar to adult ranges from 61 to 90 d at 32 C. The different nymphal instars are taxonomically described. Male and female longevities are to 54 d and 5 to 50 d, respectively. The sex ratio is slightly male biased. The predatory and mating behaviours are described. The biocontrol efficiency of this reduviid is also dealt with. Key-words: Insecta, Heteroptera, Reduviidae, Sycanus reclinatus; reduviid predator; biology; be- haviour ; biocontrol efficiency. Introduction Reduviids constitute a large group of predatory insects that could play an important role in biological control. Our understanding on the biology and behaviour of reduviids is inadequate. The present paper outlines the biology, behaviour and biocontrol potential of a voracious, entomophagous, crepuscular reduviid, Sycanus reclinatus, which is preying on pests, such as, American bollworm or the gram pod borer, Heliothis armigera HuBN.), spotted boll worms, Earias insulana BOISDUAL nd E. vitella STOLL, he tobacco caterpillar, Spodoptera litura FABRICIUS, nd the cotton stainer, Dysdercus cingulatus DISTANT. It lives chiefly on mango trees Mangifera iadica LINNAEUS) f tropical evergreen forests, adjacent to agro-ecosystems of southern India. A maximum of eighteen bugs were seen on a tree. The present study provides knowledge of biological, behavioural and biocontrol potential of S. reclinatus which could be used as a biocontrol agent for pest management programmes. 1. Materials and Methods Nymphal instars I1 to IV) of S. reclinatus were collected from the trunk of mango trees M. ndica), from Azhagarmalai tropical evergreen forests, boarding agroecosystems, in Madurai district, Tamil Nadu. They were brought to the laboratory and reared in plastic containers (6.5 cm height and 6 cm diameter) at the temperature 32 C, r.h. 80-85%; photoperiod 11 to 12 h, on adults and nymphal instars of grasshoppers Trilophidia sp.) collected from grasslands, on all the larval stages of H. armigera, E. insulana, E. vitella and on both nymphal instars and adults of D. cingulatus. The preys were supplied from laboratory cultures and also collected from cotton fields. The adults emerged were used for biological observations. The different batches of eggs deposited on the sides of the rearing containers  144 S. J. VENNISON nd D. P. AMBROSE, iology, Behaviour and Biocontrol Efficiency were separated and placed on cotton and incubated in plastic containers 5 cm height and 4 crn diameter). A wet cotton swab was kept inside the incubating containers for maintaining optimum r.h. (85%) and the swab was replaced with a fresh one occasionally in order to prevent fungal attack. Immediately after ecfosion the nymphal instars were isolated in plastic containers and reared on the above mentioned preys. Observations on incubation and stadial periods, nymphal mortality, sex ratio, oviposition, and adult longevity were made and recorded. An index of oviposition days was calculated from the percentage of egg laying days in the total adult female's life span (AMBROSE 980). Two generations of insects were thus raised in the laboratory. The predatory and mating behaviours were directly observed in adult insects kept inside the transparent rearing Containers in the laboratory. For studying the predatory behaviour adult predators starved up to 24 h and larvae of H. armigera (size, 20-25 mm long and 2.5 to 3 mm broad) were used as preys. For studying the mating behaviour, insects reared individually in plastic containers and aged 10d were used. The biocontrol potential was studied in the laboratory using both V instar nymphs as well as adults (both sexes) of the predator, S. reclinatus, starved up to 24 h. The caterpillars of pest species, such as, H armigera, E. insulana, E. vitella, S. litura, and both the V instar nymphs and adults of D ingulatus were selected for the study since these life stages of the pests are seen abundant in the agroecosystems. Pest caterpillars or the nymphs or the adults were provided one after another in the individual rearing containers (6.5 cm height and 6 cm diameter), with the predator, S. reclinatus, and the number of preys killed or preyed on in a 24 h period is recorded. Camera lucida illustrations were prepared using specimens preserved in 70 ethanol. 2. Results and Discussion 2.1. Microhabitat S. reclinutus is found in the tropical evergreen forests of Tamil Nadu. The nymphal instars live at the base of mango trees. The reduviid co-inhabitant is Sphedunolestes sp. Anoplolepis longipes JERDON as also found in the microhabitat. 2.2. Eclosion and Ecdysis The eggs (fig. 1) hatch in 14 to 23 d invariably from 10.00 to 14.00 h. The pale ochraceous nymphs turn into deep ochraceous within one hour. They do not probe the empty egg shells immediately after eclosion. The nymphs start feeding soon after they have acquired normal colouration. Congregational feeding among early nymphal instars is a common phenomenon. Table 1 presents the incubation and stadial periods, adult longevity and sex ratio of S. reclinutus for 2 generations. All the 133 nymphs observed in the laboratory moulted and emerged at night from 20.00 to 04.00 h. The incubation period ranges from 14 to 23 d (n = lo). The stadial period of I, 11,111, IV and V instars ranges from 10 to 20 d (n = 92); 5 to 14d (n = 85); 7 to 20 d (n = 83); 6 to 28d (n = 86) and 4 to 46d (n = 64), respectively. The males emerge later than the females. The total stadial period from eclosion to imaginal moulting ranges from 61 to 90 d (n = 54). 2.3. Nymphal instars Overall colour ochraceous; scape, pedicel, st flagellar segment, compound eyes, obsolete line on the apex of anteocular portion, irregular marking on the postocular portion, femora    r - Te 1 Inoasaapoaoydasao o   rclnatus GaoInopoSaapo I I  1IV V MaeVFmae I RMe _  SD nI1RMe   SD n1210   3151110   00 51213 _  27 4 1117   15 4617189   19 k  2122335172 85   15   2527456218   45312 10   2751328   62121   652141327   3394326   88 1 SaoIAAoy b  MaeMaeFmaeFmae68539273   21 _  18 _  1 08 6311512196955 55 79   27   27   1 08 771815321  146 S. J VENNISON nd D. P. AMBROSE. iology, Behaviour and Biocontrol Efficiency +I I +I I I +I ~~m~momowo~owo 0 d m N - m m CI * r- +lm N m L +I I I +I I I "9p?""9'c Y"99p?Y1 OO~O ONO~O~O~O r-m+~mr-r-wwwwm +I +I +I +I +I +I +I ?9"19p?Op?d"O?OP 00dmmwmqWq O+Om *0m0m0i0-0N0N0 I +I +I +I +I I ?9?9t9?9?999 9 r-3m 3Nflmwr--mNm 00000000+010-0 +I I +I I I I ~0 ~+0m000w-w~ 4 4 N i - * w m m r- +lm m * +I +I I +I I +I +I -Nr-mmNmmr-cOr-mmw ~O ONO~O~O~O~O ti I +I I +I +I +I I Nm-NN*r-dNwMPmw mob0m0w0wot.0M0 +I +I I +I I I I dww~bmir-mmm~w 'c o? 9 . ? c 9 p? 0000-0-0NOm0m0 Y ¶ P  Mitt. Zool. Mus. Berl. Bd. 68 (1992) 1 147 and tibiae, dorsal abdominal odoriferous glands, most of the abdominal areas and wing rudiments black, sparsely longly pilose. Head long, shining; slightyl raised postocular area longer than anteocular area; compound eyes slightly laterally protruding; 4-segmented long and slender antennae inserted near compound eyes; scarcely pilose scape longer than head; moderately pilose 1st flagellar segment very short and finely pilose filiform 2nd flagellar segment the longest; scape and pedicel bear annulations; rostrum bow shaped and robust; 1st segment subequal to anteocular portion; 2nd segment the longest and the 3rd the shortest. Protonum transversely divided before the middle, anterolateral angles of pronotum tuberculate, sparsely pilose; legs elongate and slender; fore and mid legs subequal and the hind leg the longest; tibiae without fossula spongiosae but with tibial combs, tarsi 3-segmented, 2nd segment the longest, 1st segment the shortest, strongly pilose. Abdomen longer than broad in all the instars; round, prominent odoriferous glands seen on 4th, 5th and 6th abdominal segments rounded; sparsely longish pilose (figs. 2 to 6). Morphometric analyses of nymphal instars are given in tables 2 and 3. Nymphal mortality is observed due to abnormalities during hatching and moulting. 2.4. Adult longevity and Sex ratio The males and females live’s to 54 d and 5 to 50 d, respectively (table 1). Laboratory breeding experiments show that S. reclinatus is multivoltine. The sex ratio of males and females in 2 laboratory raised generations is 1 : 0.8. 2.5. Predatory behaviour Arousal response is indicated in 0.9 min (n = 6) by the unusual posture, involving tibial juxtaposition followed by erect posture and extension of antennae and rostrum towards the prey similar to other reduviids (AMBROSE 980, 1983; HARIDASS 985; and VEN- NISON & AMBROSE, 987). Being an exclusive predator, the visual stimulus from the moving prey appears to be the primary sensory input for arousal in predation, as reported in other reduviids (LIVINGSTONE AMBROSE 978; HARIDASS ANANTHAKFUSHNAN 980). S. re- clinatus locates its preys visually. Once the arousal was accomplished, S. reclinatus orients towards the prey and remains motionless until the prey approaches the predator. If the prey is more agile and it moves away from the predator, after a few minutes of waiting, the predator approaches the prey in 0.7 min (n = 6) and pins it by inserting the rostrum into the membranous areas which results in paralysis (in 0.13 min; n = 6). By inserting the stylets at suitable place, the prey is dragged beneath the body as the predator walks forwards or by pulling the prey while the predator moves backwards. In the Geld the prey is transported to a sheltered place for interference free feeding, whereas, in the laboratory the prey is transported to a distance of about 15 cm. While feeding (figs. 7 and 8) the stylets are frequently withdrawn and reinserted at different angles as reported by AMBROSE 1980). The secretions from the accessory salivary glands partially digest the internal organs of the prey before the food is sucked in and the secretions from the main salivary glands digest the food after sucking (HARIDASS ANAN-
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