Cephalic chaetotaxy of the last instar larva of a pyralid : Syllepte derogata ( Fabricius ) ( Lepidoptera )

Lepidoptera is the second most diverse insect pest order outnumbered only by the beetles. Almost every cultivated plant is attacked by larvae of at least one lepidopteran pest. Most of the caterpillars are defoliators or leaf rollers or miners of succulent plant tissues. Identification and diagnosis of the larvae can be better with an examination of the arrangement of various setae & punctures of the head and other body segments. In this study we have followed Hinton (1946). An attempt has been made to describe the cephalic chaetotaxy of Sylepta derogata Fabricius with chaetotaxic maps.

Lepidoptera is the second most diverse insect pest order outnumbered only by the beetles.Almost every cultivated plant is attacked by larvae of at least one lepidopteran pest.Most of the caterpillars are defoliators or leaf rollers or miners of succulent plant tissues.Identification and diagnosis of the larvae can be better with an examination of the arrangement of various setae & punctures of the head and other body segments.In this study we have followed Hinton (1946).An attempt has been made to describe the cephalic chaetotaxy of Sylepta derogata Fabricius with chaetotaxic maps.

Material and Methods
Larval instars of Syllepte derogata (Fabricius) were collected from the field and reared on fresh host plant clippings in plastic containers in the laboratory up to prepupal stage.Mature larvae were boiled in water for killing and distention of the body.The distended larvae were decapitated with a surgical blade.Detached heads were kept for 8-10 hrs in 10% KOH, washed with 1% glacial acetic acid and then mounted in 70% alcohol and glycerine in 9:1 ratio.For chaetotaxic study, larval heads were transferred to a petridish containing glycerine and observed under stereoscopic microscope.

Results and Discussion
Cranium is moderately sclerotized and light brown with dark patches all over the head.Frontoclypeus longer than broad and ecdysial line joins in the middle to median epicranial suture.Stemmatal area is well differentiated from the rest of the cranium, beset with six stemmata, fifth stemmata placed at base of antenna and sixth behind fourth stemmata.All setae are spinous, arising from pinacula.
Anterior group constitutes setae A1, A2, A3 and pore Aa.A1 in level of stemmata 4, lies towards median longitudinal line; A2 posterolaterad to A1, A3 lies in level and mesad to stemmata 2; A1>A3>A2 lengthwise; pore Aa lies postrad and close to A1 than A2.The presence of the anterodorsal group has been described by many workers in different lepidopteran families, whereas, Yen et al. (2004) observed the missing of puncture Aa in a new genus Austromusotima of family Crambidae.Posteriordorsal group furnished with setae P1 and P2 along with pore Pb.P2 longer than P1.P2 posterior and almost in straight line to P1. Pore Pb anterad to P2 but closer to seta P1.Two different arrangements of these two setae and one puncture has been noticed by Yoshiyasu (1980), Diakonoff & Arita (1980), Amutha & David (1998) and Yen et al. (2004).Lateral group contains seta L1 and pore La; denotes L1 directly dorsad to stemmata 1, pore La anteromesad to L1.The presence of this seta and puncture has also been observed by Lawrence & Downy (1966), Downy & Allyn (1979), Lin (1993), Amutha & David (1998) and Solis et al. (2005), whereas, Yen et al. (2004) noticed the absence of puncture La in a new genus Austromusotima of family Crambidae.

Figure
Figure 1. a -Frontal view; b -Lateral view