朱槿上桑粉介殼蟲(Maconellicoccus hirsutus)與熱帶大頭家蟻(Pheidole megacephala)之共存關係探討

Abstract

Ten species of ants associating with hibiscus mealybug, Maconellicoccus hirsutus (Green), in Pingtung, Taiwan were observed. From those attending ants, Pheidole megacephala (Fabricius) and Tapinoma melanocephalum (Fabricius) are frequently detected in 19 townships. Thus, the associations between P. megacephala, the most common ants on hibiscus (Hibisicus rosa-sinensis Linn.), and hibiscus mealybug were studied in the laboratory. On average, after 28 days only 2.8 out of 10 mealybugs are left coexisting with ants on hibiscus in a 17×10×9 cm^3 cage. This result shows that ants prey on M. hirsutus in case they need protein and fat and there is no additional food supply. By adding 50 spider mites (Tetranychus sp.) into the cage, the amount of mealybugs fed upon by ants dropped significantly in comparison to when there were no mites added (t(subscript 0.05,18)=1.94, p＜0.05). In place of mealybugs, spider mites can serve as an alternative protein source for ants. This can also be proven by the 6-fold of decrease in the number of mites coexisting with ants after 21 days. Predatory and/or parasitic natural enemies were found in 67% of 22 nests constructed by P. megacephala at the stem base of hibiscus. Generally speaking, only female adults and eggs of M. hirsutus could be found inside those nests. The comparison of the preference of P. megacephala for egg, nymph and adult of M. hirsutus indicated that ants do not consume adults and have a significant preference for eggs over nymphs (t(subscript 0.05,20)= 3.01, p=0.002). Because the tests also showed that ants did not influence the egg production of female adults, we presume that the eggs and the adults of M. hirsutus found in the nest are the protein and honeydew, respectively, resources of the ants. The observation of the protective behavior of P. megacephala against the attack of Cryptolaemus montrouzieri Mulsant on mealybug showed that all C. montrouzieri introduced were killed and removed in 132.5 min. The mealybugs that associated with ants are indeed protected from attack by their predatory natural enemies, although mealybugs and ants do not have an intimate association.