## 4 Discussion
### Variety Effects on Egg Parasitoids  
Unlike the parasitoids of free-living herbivore stages, egg parasitoids must encounter immobile life-stages that do not, by themselves, damage the host plant [33]. In the case of BPH, WBPH and GLH, the eggs are further concealed beneath the host parenchyma [55]. Egg parasitoids therefore rely on a range of chemical cues to locate their hosts. These are mainly induced volatiles emitted from herbivore damaged plants [37; 72; 73; 74]. For egg parasitoids, volatile-inducing damage is predominantly related to feeding activities of the adult planthoppers or leafhoppers, although parasitoids will also respond to cues emitted after attack by planthopper nymphs [74]. Much recent research has focused on identifying the volatiles emitted from BPH damaged rice plants [37; 75; 76]. However, there is still little knowledge of the chemical ecology of egg parasitism. [PERSON] et al. (2005) [74] have shown that the egg parasitoid _Anagrus nilaparvatue_ [PERSON] is attracted to rice plants on which BPH are feeding; several plant volatiles appear to play a role in this attraction. Furthermore, rice plants treated with jasmonic acid (JA) have been shown to emit a range of volatiles associated with the attraction of _A. nilaparvatue_, and BPH eggs in rice plants that are surrounded by JA-treated plants are more vulnerable to the egg parasitoid [73]. However, [PERSON] et al. (2006) [37] have also shown that the range and number of volatiles emitted from rice are strongly influenced by variety. In a comparative study, _A. nilaparvatate_ parasitized fewer eggs on IR26 and IR64, both varieties with the _Bph1_ gene for resistance, compared to eggs in susceptible varieties without BPH resistance genes [37]. Parasitism was also generally higher in JA-treated susceptible plants compared to JA-treated resistant plants [37]. Volatile blends therefore strongly influence parasitoid attraction to infested plants.  
We predicted that parasitism of eggs in IR64 would be higher than in IR62. We based our predictions on previous research by [PERSON] and colleagues [37] that suggested resistant plants may be less attractive to egg parasitoids, and on the likely lower densities of eggs on resistant rice. However, we also expected that IR62, which has high antibiosis defenses, would either have a lower requirement for semiochemical lures, compared with susceptible varieties, or would release fewer volatiles during attack because of resistance-induced changes in planthopper feeding behaviors. In support of our predictions, we found that total parasitism of BPH eggs was higher on IR64 than IR62 during the wet season exposures (Figure 2, Table 2). Furthermore, parasitism of BPH eggs by _Anagrus_ spp. was higher on IR64 than on IR62 (Figure 3A,B, Table 2), with a tendency toward higher _Oligosita_ spp. parasitism on IR64 in the same experiment (Figure 3D), and significantly higher _Oligosita_ spp. parasitism on eggs in IR64 in the honeydew experiment (Figure 4, Table 2). Parasitism of WBPH eggs by _Oligosita_ spp. also tended to be higher on IR64 (Figure 3). As discussed previously, higher parasitism of eggs in IR64 cannot be attributed to density effects at the plant level (Table S1). It is more probable that the differences are associated with the dissimilar behaviors of planthoppers on the varieties. As indicated in a previous study, whereas BPH oviposit similarly on IR62 and susceptible varieties during initial oviposition cycles, the feeding behavior of adult females on resistant and susceptible varieties differsconsiderably [61]. Planthoppers on resistant rice will probe more than on susceptible rice, they also have shorter feeding bouts and produce less honeydew [77]. Each of these factors could influence the nature of volatiles emitted from infested rice plants and ultimately affect egg parasitism. We examined the potential for one of these possible factors, honeybee composition, to influence parasitism rates.