The Biology and Ecology of the Yellowmargined Leaf Beetle, Microtheca Ochroloma Stal, (Coleoptera: Chrysomelidae) on Crucifers.

The biology and ecology of the yellowmargined leaf beetle, Microtheca ochroloma Stal, were studied on cabbage, Brassica oleracea var capitata L., collard, B. oleracea var acephala L., mustard, B. juncea Cosson, turnip, B. rapa L., and radish, Raphanus sativus L. The life cycle of the beetle consists of an egg stage, four larval instars, prepupal, pupal and adult stages. There were no significant differences in the effect of host plant on duration of development of immature beetles (p = 0.3353). The mean duration of development from oviposition to adult emergence ranged from 26.6 d on turnip to 27.5 d on cabbage. There was however a significant effect of host plant on multi-generation survivorship. Beetles reared on cabbage did not survive beyond the second generation. With respect to adult beetles, significant differences were found in the effect of host plant on fecundity (p = 0.0057) and longevity (p = 0.0001). The mean fecundity of females was significantly higher for beetles maintained on turnip (490.74 $\pm$ 116.04) than for those maintained on collard (198.85 $\pm$ 28.94). There were no significant differences in the mean fecundities of females maintained on cabbage (271.25 $\pm$ 39.11), mustard (424.95 $\pm$ 46.39) and radish (440.05 $\pm$ 50.09). Beetles fed radish lived significantly longer than beetles fed each of the other host plants. There were no significant differences in the longevity of male and female beetles by host plant. In choice tests for feeding preference, both the third larval instar and adult beetles showed strong preference for the foliage of turnip and mustard. Collard and cabbage were least preferred. Susceptibility of beetle larvae to insecticides was esfenvalerate $\u3e$ carbaryl $\u3e$ malathion. There were no significant differences in the effects of host plant on susceptibility of the larvae to the insecticides. There was however a 10-fold difference in the activities of glutathione S-transferases enzymes for beetle larvae fed collard and those fed turnip. Spatial distribution studies revealed that both immature and adult beetles have aggregated spatial patterns on field planted mustard

Feeding preferences of Microtheca punctigera (Achard) (Coleoptera: Chrysomelidae) for some Brassicaceae plants in multiple-choice assays

Preferência alimentar é informação básica importante para o desenvolvimento de estratégias de manejo. Experimentos de preferência alimentar com múltipla chance de escolha foram conduzidos em laboratório para o crisomelídeo Microtheca punctigera (Acherd). A alimentação foi avaliada 72h após o início dos experimentos. Com uma larva por placa de Petri, foram utilizadas discos de folhas de almeirão, Nasturtium officinale L., rúcula, Eruca sativa L., mostarda, Brassica juncea Cosson, couve chinesa, B. pekinensis (Lour.) Rupr., e nabiça (Raphanus raphanistrum L.). A alimentação em ordem decrescente foi em couve chinesa, mostarda, nabiça, rúcula e almeirão (7,97; 1,85; 0,98; 0,36 e 0,11 mm², respectivamente). A alimentação em couve chinesa foi de 4,31 vezes maior do que em mostarda. O mesmo experimento foi repetido com um adulto por placa. Respostas de machos e fêmeas foram similares. A alimentação foi maior em mostarda (87,2 e 142,8 para machos e fêmeas, respectivamente); em rúcula (51,5 e 132,7) e couve chinesa (51,8 e 89,0) foi intermediária. Agrião (22,96 e 39,3) e nabiça (12,03 e 28,4) foram os menos consumidos. Num terceiro experimento, dez larvas por placa foram usadas, incluindo-se também espinafre, Tetragonia expansa Murr., rabanete, Raphanus sativus L., e couve, B. oleracea var. acephala L. A freqüências diárias de larvas em cada alimento foram também medidas. A alimentação foi similar em couve chinesa e mostarda (47,89 e 53,78, respectivamente). O número de insetos foi maior em mostarda, couve chinesa e nabiça. Prováveis explicações da preferência e proposições de novas pesquisas são discutidos.Host plant feeding preference is important basic information for the development of insect management strategies. Multiple-choice feeding preference assays were conducted in the laboratory for the chrysomelid beetle, Microtheca punctigera (Achard). Feeding was assessed 72 h after onset of experiments. With one larva per Petri dish, food items comprised watercress, Nasturtium officinale L., arugula, Eruca sativa L., mustard, Brassica juncea Cosson, Chinese cabbage, B. pekinensis (Lour.) Rupr. and wild radish (Raphanus raphanistrum L.). Feeding ranking preferences were Chinese cabbage, mustard, wild radish, arugula and watercress (7.97, 1.85, 0.98, 0.36 and 0.11 mm², respectively). Feeding on Chinese cabbage was 4.31 times more intense than on mustard. The same experiment was repeated with one adult per dish. Responses of males and females were quite similar. Feeding was higher on mustard (87.2 and 142.8 for males and females, respectively). Feeding on arugula (51.5 and 132.7) and Chinese cabbage (51.8 and 89.0) were intermediate. Watercress (22.96 and 39.3) and wild radish (12.03 and 28.4) were the least preferred host plants. In a third experiment, ten larvae per dish were used and spinach, Tetragonia expansa Murr., radish, Raphanus sativus L. and collard, B. oleracea var. acephala L., were also included. Daily larval frequencies on each food were also measured. Feeding was similar on Chinese cabbage and mustard (47.89 and 53.78, respectively). Number of insects was greater on mustard, Chinese cabbage and wild radish. Probable explanations for results and proposals for further investigations are discussed