**3.3 The flagellum**

It consists of six segments; the first five segments known as the funicle (resemble the pedicel in form), while the sixth flagellar segment is known as the club (Fig.1). Six subtypes of sensillae were recognized on the funicle, S. trichodea 1, 2, 3, S. chaetica 2 and S. coeloconic 1, 3. The characteristic morphological features of sensilla are shown in figures (2D, 3A).

### **3.4 The club**

It is the last segment of flagellum (similar to funnel in shape), longer and broader than other antennal segments (Fig.1). The light microscopic observation revealed that the sensilla are densely and homogenously packed on this area. Also, the electronic microscopic study revealed the presence of four types (seven subtypes) of sensilla highly crowded over the whole of this segment.

Fig. 1. General morphology of adult antenna *Rhynchophorus Ferrugineus* showing: Scape (S), Pedicel (P), Funicle (F) and Club (C). [Scale bar indicate 1 mm]

Ultrastructure Alterations in the Red Palm Weevil Antennal Sensilla Induced By Gamma Irradiation 233

Fig. 2. SEM photomicrographs of non-irradiated adult antenna of *Rhynchophorus Ferrugineus.*  (A): Sensilla coeloconica 1 (C1) on the scape, (B): Sensilla coeloconica 2 (C2) on the pedicel, (C): Sensilla basiconica 1(B1) on the ventral side between scape and pedicel, (D): Sensilla trichodea 1, 2, 3 (T1, T2, T3), Sensilla chaetica1 (Ch1) and Cuticular pores as arrowheads on

The sensilla of this type are straight, and tapering to a fine point. In some sections, a socket of cuticle is found close to the base of the sensilla. The length measures about 70 µm and the diameter about 12.5 µm (Fig. 2D). Sensilla trichodea 1, 2, 3 observed on the lateral side of the

the funicle. [Scale bars indicate 100 µm (A, D) and 10 µm (B, C), respectively]

club without any arrangement and have been described previously (Fig.2D).

**3.5.3.3 Sensilla trichodea 3** 
