Abstract We surveyed insect galls in an area of Cerrado sensu stricto and Gallery forest in the municipality of Caetité (BA) to contribute to current knowledge of the local flora and its associated gall-inducing insects. Monthly collections were made between February/2015 and January/2016, totaling 12 field campaigns (involving two or three people and lasting four hours) that followed an established path through the countryside. A total of 63 gall morphotypes were identified on 47 host plant species belonging to 22 families; 17 morphotypes were found in the Gallery forest and 46 in Cerrado vegetation. The plant families showing the greatest gall richness were Leguminosae (n=15), Myrtaceae (n=9), and Asteraceae (n=7). The species with the greatest number of galls was Mimosa gemmulata Barneby (Leguminosae) (n=3). Most galls were observed on leaves (66%) and stems (24%); they were mostly green (49.3%) or brown (26%), with globoid shapes (39.7%) or marginal roll (17.4%), and were unilocular (87%), glabrous (62%) and isolated (89%). Cecidomyiidae (Diptera) were the principal gall-inducing insects. The associated fauna was principally composed of Hymenoptera. Eight plant taxa were recorded for the first time as hosts of galling fauna.

RESUMO Insetos galhadores podem alterar o padrão anatômico dos tecidos das suas plantas hospedeiras, induzindo morfotipos peculiares de galhas. Neste estudo, as modificações estruturais observadas nas galhas de Lopesia sp. em Mimosa tenuiflora assemelham-se àquelas evidenciadas em outras galhas de Cecidomyiidae, com dois compartimentos teciduais. No entanto, as camadas de parênquima no compartimento interno entre a zona mecânica e o tecido nutritivo são peculiares. O desenvolvimento da galha não bloqueia a síntese de quaisquer compostos detectados nos tecidos não galhados de M. tenuiflora, por meio de testes histoquímicos. Ligninas, polifenóis, alcaloides e terpenoides foram detectados no compartimento externo, sugerindo seu envolvimento na defesa química das galhas. Proteínas, açúcares redutores e lipídios foram detectados tanto no compartimento externo quanto no interno, e o tecido nutritivo é rico em açúcares redutores. Esse perfil está ligado à nutrição do galhador. O ambiente da Caatinga parece não impor restrições ao desenvolvimento da galha, mas, a parede celular periclinal espessa e o parênquima homogêneo parecem contribuir para o controle da umidade e da radiação, favorecendo à sobrevivência do inseto galhador.

ABSTRACT Gall-inducing insects can change the anatomical pattern of host plant tissues by inducing peculiar gall morphotypes. In this study, the structural changes observed in Lopesia galls on Mimosa tenuiflora resemble those found in other Cecidomyiidae, with two tissue compartments. Nevertheless, the parenchyma layers of the inner compartment, between the mechanical zone and the nutritive tissue, are peculiar. Gall development does not impair the synthesis of any compounds detected by histochemical tests on non-galled tissues of M. tenuiflora. Lignin, polyphenols, alkaloids and terpenoids were detected in the outer compartment, suggesting their involvement in chemical defence of galls. Proteins, reducing sugars and lipids were detected both in outer and inner compartments, whereas nutritive tissue is rich in reducing sugar. This profile is linked with the nutrition of the gall-inducing insect. The Caatinga environment does not seem to constrain the development of galls, but the thick periclinal cell wall and homogeneous parenchyma may contribute to the control of humidity and light radiation, thus favouring the survival of the gall-inducing insect.