Figure 1.
Anal excretion and oviposition behavior of the Asian citrus psyllid.
A–C. Adults and nymphs feeding and producing their honeydew (arrows) on citrus leaves; note large clear drop produced by the male (in A), whitish pellet by the female (in B), and long whitish tubes/ribbons of nymphs (in C). D. Ventral view of the abdomen’s posterior end of 5th instar nymph, showing honeydew (arrow) oozing out from the anus and circumanal ring (cr), and the long circumabdominal setae (cs). E. Newly molted nymph (arrowhead) leaving a long ribbon of honeydew (arrow) still attached to the exuvia (ex). F–H. Still micrographs taken from videos: F, a male depositing its clear honeydew droplet (arrow) gently on top of a previously excreted drop (double arrows); G, a female propelling its whitish pellet (arrow) dorsally and to the side with other previously propelled pellets (double arrows); H, a female laying eggs (double arrows), one leaf was removed at the position of the asterisk to expose eggs laid between the young shoot and the petiole of that leaf). Abbreviations: cr, circumanal ring; cs, circumabdominal setae; ex, exuvia; ov, ovipositor valvulae.
Figure 2.
Structure of the anal area in nymphs and adults of the Asian citrus psyllid.
A–F. Scanning electron micrographs (SEM) of nymphs (A–C, ventral views) and adult females (D–F. dorsal views) showing position of the circumanal ring (cr) around the anus (an) near the posterior end of the abdomen (boxed areas in A and D). In B & C (nymphs), note the ornate cuticular ridges around that ring (arrows), wax pores (wp), and the narrow cuticular slits (sl) with wax filament (wf) oozing out. In E & F (females), note the outer and inner rows (or & ir, respectively) of wax pores and the waxy material (wm) coming out of these pores (in E). G–I. Light and scanning electron micrographs (lateral, dorso-lateral and dorsal views, respectively) of D. citri males showing the anal tube (at), anus (an), aedeagus (ae), and lateral plates (lp); note lack of the circumanal ring or any cuticular ridges or wax pores around the anus. J. SEM of a male’s honeydew droplet (on a citrus leaf) showing no filamentous structures on the surface like those found on the honeydew of nymphs or females. Other abbreviations: at, antenna; cs, circumabdominal setae; st, stylets.
Figure 3.
Scanning electron micrographs of waxy structures on the surface of honeydew and circumabdominal setae of the Asian citrus psyllid.
A. Honeydew tube (arrow) attached to the exuvia (ex) of a fifth instar nymph (dorsal view); note long circumabdominal setae (cs) around the abdomen. B & C. Higher magnifications of the wax filaments (wf) found on the surface of the nymphal honeydew oozing out of wax pores in the circumanal ring (cr). D & E. Details of the bases of the circumabdominal setae (cs) of 5th instar nymphs, showing the waxy material covering these setae (arrows). F. Adult female pellet (slightly open at the center) showing the wax structures (ws) on the surface, and gluey material devoid of filamentous structures inside (asterisks). G & H. Higher magnifications of the wax structures (ws) as filaments or ribbons on the surface of female pellets.
Figure 4.
FTIR microscope reflection spectra of the surface of male, female and nymphal honeydew excretions (top three panels) compared to attenuated total reflectance FTIR spectra of typical monosaccharides.
The honeydew spectra contain many peaks attributable to simple saccharides, especially the broad peak centered at 3300 cm−1 attributable to the O–H bonds in sugars and water, and broad poorly resolved peaks at frequencies lower than 1500 cm−1 which indicate a mixture of the saccharides whose spectra appear in the lower three panes. However, the peaks at 2850 and 2910 cm−1 are more pronounced in the honeydew and the peak at 1733 cm−1 does not appear in the saccharide spectra. The male excreta show spectra typical of aqueous sugars.
Figure 5.
FTIR microscope reflection spectra of the surface of male, female and nymphal honeydew (top three panels) compared to attenuated total reflectance FTIR spectrum of beeswax, a typical ester wax.
While all the honeydew spectra are dominated by saccharide peaks (as shown in Fig. 4), the female and nymphal honeydew spectra are markedly different from that of the male. Peaks at 2850 and 2910 cm−1 (which are attributable to C–H bonds in a long chain aliphatic molecule) and the peak at 1732 cm−1 (which is attributable to the C = O of an ester carboxyl group) strongly indicate the presence of an ester wax on the surface of honeydew of females and nymphs.