Biological and Morphological Parameters of Trilocha varians (Lepidoptera: Bombycidae) in Pakistan

| The biology and morphology of Trilocha varians was studied on Ficus benjamina (L.) under the laboratory conditions. The results on different biological and morphological parameters showed that the fecundity of female ranged from 160 to 281 which increased its survival rate. Trilocha varians has five larval instars. The last instar changed its colour to dark reddish and look like branches of host plants. The male and female mean longevity was 6.0 ± 1.171 and 11.4 ± 1.70 days. Pale reddish brown lines were present on the dorsal side of female forewings. Female forewings were broader than male wings with dark reddish brown thorax, head and abdomen. Adult hind wings were grayish with reddish brown outer margins. The biological and morphological information of Trilocha varians described in current paper will lead to proper management practices during peak reproductive period of insect to avoid pest outbreak. Novelty Statement | Trilocha varians is emerging pest of ornamental plants especially Ficus species that not only planted to increase the aesthetic value of country but also use as fruits and medicine. There is need to control this destructive pest of ornamental plants in Pakistan to min-imize the losses. The biology and morphology informations are very important before adopted any strategy against this pest. For this purposes, the current study was conducted and this is first study on this pest in Pakistan.


Introduction
F icus benjamina (Rosales: Bombycidae) (Zolotuhin and Witt, 2009), commonly known as weeping figs having medicinal value (Kumar et al., 2012) and used for the removal of gaseous formaldehyde from indoors (Kim et al., 2008). It is planted alongside the road as ornamental plant and native to tropical and subtropical regions of the world. During the study, it was found to be infested by many insect pests such as mealy bug, whitefly (Walton and Pringle, 2004;Avery et al., 2011) and a lepidopteran caterpillar, Trilocha varians (Walker, 1855).
Before this study, no such type of study has conducted on this pest in Pakistan. For this purpose, this study is conducted to check the biological and morphological parameters of T. varians under laboratory conditions in Pakistan.

Study area
The present study was conducted at Institute of Plant Protection, MNS-University of Agriculture Multan. The study area is located at 71.4 0 longitude E and 30.2 0 latitude N with arid and semi-arid areas. There are four seasons in Pakistan: dry, cool winter from December-February; dry, hot spring from March-May and summer monsoon season with high rain from June-November. June and January are the hottest (35 °C) and coldest (13 °C) months of Pakistan.

Insect collection
The immature stages such as eggs and larvae were collected from F. benjamina plants planted along the boundary walls of MNS-University of Agriculture, Multan during 2019.

Leaf collection and culture maintenance
Different collected stages were brought to Rearing laboratory at University for rearing purpose. The plastic containers were purchased from nearby market and each stage of pest kept into separate container. The new and fresh F. benjamina leaves were cut with the help of secateurs and placed into containers containing T. varians larvae.
On daily basis, old leaves food was changed and provided new leaves for larvae feeding. Newly hatched larvae were kept into separate petri dishes which purchased from nearby market. The larvae were converted into pupae and converted into adults. The one pairs of adults were placed into rearing cage for egg lying purposes and a napliner placed inside the cage for collection of eggs. Number of eggs was counted on daily basis and recorded the number of days from egg lying to hatching. On daily basis, eggs were collected early in the morning and individual egg placed into separate petri dishes. For this purpose, 50 petri dishes were used and one larva placed in each petri dish to record the developmental period and hatching time. Culture of T. varians was maintained at 26±2°C, 65±5% temperature and relative humidity (RH), respectively with 14:10 photoperiod.

Results and Discussion
Different developmental parameters like biological and morphological were recorded during the study period. The study revealed that female adult was long lived as compared to male adult. The male and female mean longevity was 6.0 ± 1.171 and 11.4 ± 1.70 days (Table 5). Pale reddish brown lines were present on the dorsal side of female forewings ( Figure 1). Female forewings were broader than male wings with dark reddish brown thorax, head and abdomen. Adult hind wings were grayish with reddish brown outer margins. The clear difference was observed between both sexes on the basis of wing venation (Table 6).  During the whole study, female was mated only once in her whole life period and died within 7-13 days. The study resulted that mating was taken place within half an hour of adult emergence and continued for several hours. During the study, it was also observed that female laid 210.7 ± 32.59 eggs on the upper surface of leaves in rows ( Figure 2) under natural conditions while on the surface of container walls.
The newly laid eggs were look like candy (flat) and pink in shape and colour while before hatching changed

Figure 2: Eggs of Trilocha varians on Ficus leaf.
The mouth and abdomen of newly hatched larvae were blackish brown and two light green dots present on the dorsal side of mouth. The lateral side of neonate larvae was black and the dorsal side of whole body covered with white hairs which removed after one days of hatching. The colour of 1 st instar larvae was remained grayish white till to fourth instar. A short and narrow long horn was present on eighth abdominal potion/ segment in each instar larvae which reduced in later in stars like 5 th . There was difficult to locate final instars of T. varians due to their resemblance with young branches of F. benjamina (Figure 3).

Figure 3: Larva of Trilocha varians.
The current study resulted that 12-16 days were the total duration of larval instars. The length and width of head capsule, length and body length of different larval instars was described in detail (Table 2). Larvae spun on the leaves and the pupation took place in boat-shaped silken cocoon. The colour of new pupated larvae was whitish yellow and changed into blackish brown prior to adult conversion (Figure 4).

Figure 4: Pupae of Trilocha varians.
The length of male and female cocoon was 9.69±1.02 and 10.60±0.73 days, respectively. The width of male and female cocoon was 4.90±0.53 and 5.67±0.62 days, respectively (Table 3) while 7.91±0.65 and 9.90±1.00 was the length of male and female pupae ( Table 4). The weight of dead moth and pupa was recorded 0.008g and 0.006g.  Range 6.50-9.00 2.50-3.20 8.00-11.00 3.10-4.00  The biological and morphological parameters on the present pest that belongs to order, Lepidoptera and Bombycidae family were studies under laboratory conditions. The maximum pest infestation was observed from October to December months. It was observed that later instars (4 th and 5 th ) caused 90-100 % defoliation in weeping fig, F. benjamina. Our findings are in line with the findings of earlier researchers (Singh and Brar, 2016;Ramzan et al., 2019) they reported 100% defoliation. The eggs of the pest were yellow in colour and our observations are similar to others scientists (Daimon et al. 2012;Ramzan et al., 2019). Singh and Brar (2016)  This pest is needed to control this emerging pest by using different biological fauna (parasitoids and predators). The present study findings are in line with many researchers study findings (Rajavel and Shanthi, 2007;Udayagiri, 1988).
During the study, many other insect pests such as whitefly, mealy bug and scale were also observed that attack on the F. benjamina. Among all these pests, the maximum infestation of T. varians was observed and whole plant died during severe attack of this emerging pest.
The environmental factors are also affecting the life cycle of insect pests such as T. varians. A study was conducted to determine the effect of temperature on the biological parameters of T. varians under controlled and uncontrolled conditions in various regions of the world including Pakistan (Ramzan et al., 2019). The study revealed that life cycle of pest was increased during low temperature (Navasero and Navasero, 2014) while reduced during high environmental conditions (temperature) (Ramzan et al., 2019;Basari et al., 2019). The life period of T. varians was increase during monsoon season (October-March) because these months are favorable for larval feeding and host availability. In these months, larvae feed vigorously and developmental period was prolonged. The similar findings have been observed by many others workers (Lu et al., 2016;Sibly et al., 2016).

Conclusions and Recommendations
The study provides basic information about the biology and morphology of T. varians. The results of current study are important for future management of T. varians population especially in Pakistan.