A possible territorial or recognition behavior of Leptoglossus zonatus (Dallas) (Heteroptera, Coreidae).

RESUMO: Provável comportamento territorial ou de reconhecimento de Leptoglossus zonatus (Dallas) (Heteroptera, Coreidae). O percevejo coreídeo Leptoglossus zonatus (Dallas, 1852) é freqüente na cultura do milho (Zea mays L.) no Brasil e tem sido observado voando e pousando sobre objetos ou pessoas que se aproximam do seu habitat. Durante o mês de janeiro de 1995, estudou-se esse comportamento em lavoura de milho. Os resultados indicaram que os percevejos concentraram-se, de forma crescente, sobre objetos (armadilhas de plástico cilíndricas) introduzidos em seu habitat nas primeiras 24 horas. Gradualmente, entretanto, com o passar do tempo (8 dias), esse provável comportamento territorial ou de reconhecimento diminuiu e tendeu a desaparecer.The coreid Leptoglossus zonatus (Dallas, 1852) is commonly found in corn (Zea mays L.) fields in Brazil, and it has been observed flying and landing on objects or persons near these fields. During January, 1995, this behavior was studied in corn plantations. Results indicated that the bugs concentrated on objects (plastic cylinders traps) intoduced into their habitat and that their number increased during the first 24 hrs. However, as time passed (8 days), this possible territorial or recognition behavior gradually decreased, and tended to disappear

Danos do percevejo barriga-verde Dichelops furcatus (F.) (Hemiptera: Heteroptera: Pentatomidae) em plantas de trigo em diferentes fases do desenvolvimento.

Orientador: Antônio Ricardo Panizzi

Comportamento alimentar de percevejos pentatomídeos através do monitoramento eletrônico pelo uso do EPG.

Orientador: Antônio Ricardo Panizzi

Probing behavior of dichelops furcatus (F.) (Heteroptera: Pentatomidae) on wheat plants characterized by electropenetrography (EPG) and histological studies.

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Electropenetrographic comparison of feeding behavior of dichelops furcatus (Hemiptera: Heteroptera: Pentatomidae) on soybean and spring cereals .

We used electropenetrography to quantify and compare counts and durations of selected waveforms, produced by adult females of the stink bug Dichelops furcatus (F.). Insects fed on immature soybean pods and immature seed heads of four spring cereals: wheat, black oat, barley, and rye. On all foods, bugs spent over 60% of their plant access time in non-probing activities. This total waveform duration was significantly longer on barley and rye compared to those on soybean and oat; wheat was intermediate. Considering only probing activities, bugs spent longer durations (ca. 2×), on soybean and oat compared to barley, rye, and wheat plants. Bugs produced significantly more pathway events on soybean and rye than on wheat and barley; with a significantly shorter duration per event on rye. The counts and durations of xylem ingestion did not differ among foods. Cell rupturing activities on seeds were longer on soybean (ca. 23%) and oat (ca. 21%), than on barley and rye (ca. 6%). The durations of ingestion events on seeds were significantly shorter on soybean (over 3×) compared to those on barley and wheat; oat and rye were intermediate. However, the ingestion duration per insect did not show significant difference among foods. Results demonstrated that D. furcatus spent more time overall in probing activities on soybean and oat; whereas, rye and barley presented the worst feeding behavior. This study provides important background information for further quantitative studies of stink bugs on different plants, such as development of resistant host plants. Key words: crop plant, feeding behavior, electrical penetration graph, electropenetrograph

Three new host plants of Edessa loxdalii (Hemiptera:Heteroptera:Pentatomidae) and notes on its rearing in the laboratory.

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Body position of the stink bug Dichelops melacanthus (Dallas) during feeding from stems of maize seedlings.

The Neotropical green-belly stink bug, Dichelops melacanthus (Dallas) is a major pest of maize, Zea mays L. in the main production areas of Brazil. It usually feeds on the stems of young plants (seedlings) causing heavy damage by affecting the plant growth and mitigating seed yield. Laboratory studies were conducted to determine body position (upward or downward) of the bug on plant (seedling) stem during feeding and not feeding activities. Ten visual records were taken per day, each spaced one hour during 30 days of 10 adult bugs of similar age exposed to maize seedlings inside cages (plastic tubes). At each observation, it was recorded if the bug was feeding on the stem (i.e., stylets inserted into the plant tissue) or not, and its body position. During feeding, waveforms were recorded using the EPG (electropenetrography) technique, which were correlated with histological studies to reveal the feeding sites. Results indicated that when they were feeding, the majority of the bugs were in the downward position. In contrast, when the bugs were on the plants, and not feeding, they were mostly in the upward position. Waveforms generated using the EPG coupled with histological studies demonstrated that during ingestion bugs fed from the xylem vessels and from the parenchyma tissue using cell rupture strategy in the latter. No clear explanation was found to explain the preferred downward body position during ingestion, but some hypothesis are speculated. Keywords: Heteroptera, Pentatomidae, feeding behavior, EPG, plant histology. Posição do corpo do percevejo Dichelops melacanthus (Dallas) durante a alimentação em hastes de plântulas de milho O percevejo barriga-verde, Dichelops melacanthus (Dallas) é uma praga importante do milho, Zea mays L. nas principais áreas produtoras do Brasil. Usualmente alimenta-se nas hastes de plantas jovens (plântulas) causando danos severos no seu crescimento e reduzindo o rendimento de grãos. Estudos foram conduzidos em laboratório para determinar a posição do corpo (voltado para cima ou para baixo) dos percevejos nas hastes das plântulas de milho durante as atividades de alimentação e não-alimentação. Foram feitas dez observações por dia, espaçadas por uma hora, durante 30 dias em 10 percevejos adultos com idade semelhante sobre plântulas de milho colocadas em gaiolas (tubos de plástico). Em cada observação, anotou-se se o percevejo estava se alimentando (i.e., estiletes bucais inseridos no tecido vegetal) ou não, e a posição do corpo. Durante a alimentação, ondas eletromagnéticas foram registradas utilizando-se o EPG (técnica da eletropenetrografia), as quais foram correlacionadas com estudos histológicos para revelar os locais de alimentação. Os resultados indicaram que quando os percevejos estavam se alimentando, a maioria estava voltado para baixo. Em contraste, os percevejos sem se alimentar nas plântulas estavam a maioria voltados para cima. As ondas geradas pelo EPG junto com os estudos histológicos revelaram que os percevejos se alimentaram dos vasos do xilema e do tecido parenquimatoso usando a estratégia de ruptura celular no último. Não foi encontrada uma explicação clara para a preferência dos percevejos em se alimentarem na posição voltados para baixo, mas algumas hipóteses são especuladas. Palavras-chave: Heteroptera, Pentatomidae, comportamento alimentar, EPG, histologia da planta