O. Merkl szerk.: Folia Entomologica Hungarica 68. (Budapest, 2007)

SHIMADA et al. (2001) reported first that, contrary to the larvae of Bruchus and Callosobruchus PlC, 1902, larvae of the genus Megabruchidius did not bore into the seeds immediately after hatching. Examining the inside of infested Gleditsia pods, along the suture of the pod there were burrows (perfectly round in cross-section) in the natural, cavity-like inner structures of the pod. A dead Lj larva was also found there, proving that the larvae migrate within the pod. In one seed it is possible for a second individual to develop, but the size of the latter can be as small as one-third of the fully developed adult. These second individuals are able to mate and produce viable offspring (T. JERMY, personal communication). However, the inside of a seed is almost entirely used up by the first individual, so there is little left for the development of a second larva. At room temperature (23 ± 1.5 °C) the development from egg to adult takes about 50 to 80 days with considerable individual variability (T. JERMY, personal communication). The population of M. tonkineus resists cold winters (JERMY et al. 2002). Rearing from pods (approx. 30 pods) picked from the ground (some even remained from the previous year) resulted in 40 males and 68 females emerging. From the same sample I took 122 seeds that were soaked in water for a day and were dissected under a microscope. 32 larvae, 76 adults and 7 pupae were found, 4 seeds were uninfested and 3 were already empty. Adults already made an operculum, but died before emergence, apparently because of unfavourable conditions. The seven pupae found were in different stages of development, 4 were already dead, as were all the larvae. In the course of the rearing experiments, not a single parasitoid wasp was ever found. Host plants - The first data on the host plants of M. tonkineus were published by WENDT (1980). She reported that two specimens were sent to her (Zoologisches Museum, Berlin) for identification from a hotel in Chemnitz. The sender supposed that the specimens had been introduced with white beans (Phaseolus sp.) from Vietnam, since such beans were stored in the same hotel room. In order to check that supposition, ten Hungarian and foreign bean varieties were tested in the Plant Protection Institute of the Hungarian Academy of Sciences, Budapest. The Lj larvae penetrated into the seeds of all varieties, some 15% of the larvae reached the undeveloped L2 instar, but all died. Similarly, the L\ larvae died in the seeds of Dolichos lablab, Glycine max, Lathyrus sativus, and Pisum sativum. However, in laboratory egg laying was observed on the seeds of Gleditsia caspica, délavai, fer ox, japonica, macroacantha, and Gymnocladus dioicus, and the larvae developed into adults (T. JERMY, personal communication). JÁNOS BODOR (editor of the horticultural magazine Kertészet és Szőlészet in Budapest) also conducted rearing experiment with beans resulting in no adult emerging, either. Various species of Gleditsia (including G. triacanthos) and Gymnocladus contain 5-hydroxypipecolic acid (REHR et al. 1973) and triterpenoid saponins (KONOSHIMA etal. 1995), which are toxic to the non-adapted seed beetles and other seed predators. However, these apparently do not affect M. tonkineus. Species of the genus Gleditsia originally occur in the Americas and Asia. In the New World a rather distantly related seed beetle species, Amblycerus robiniae (FABRICIUS, 1781) (tribe Amblycerini) is specialisedon Gleditsia triacanthos (SOUTHGATE 1979). In Hungary, this species was observed once, introduced with seeds of thornless honey locust tree ("inermis", a cultivar of uncertain status) from North America (MERKL 2001). Dl-IORIO (2005) mentioned another species, Bruchidius endotubercularis ARORA, 1980 infesting pods of Gleditsia triacanthos in Argentina. This Asian species, known to occur in India and Vietnam, was accidentally introduced into Argentina.