ECOLOGY AND POPULATION BIoLoCY Natural History of a Gall-Inducing Weevil Collabismus clitellae (Coleoptera: Curculionidae) and Some Effects on its Host Plant Solanum lycocarpum ( Solanaceae ) in Southeastern Brazil ANDREA LUCIA TEIXEIRA DE SOULA,1, 2 GERALDO WILSON FERNANDES,2 JOSE EUGENIO CORTES FIGUEIRA,2 AND MARCEL OKAMOTO TANAKA' Ann. Entomol. Soc. Am . 91(4): 404 - 409 (1998) ABSTRACT The phenology , general characteristics , and mortality factors acting upon the weevil Collabismus clitellae Boheman in a population of Solanum lycocarpum St. Hil. (Solanaceae) were investigated in southeastern Brazil , as well as its distribution and impact on the host plants. Mating and oviposition of the weevils were observed in the beginning of the summer , with larval devel- opment until the autumn and emergence in spring . Most galls were found toward the base on plants 0.9-1.2 m high, a distribution perhaps the result of physiological differences between plants of different height . Natural enemies also may influence this pattern ; logistic regressions showed that greater gall size and increased height above the ground increased mortality caused by the wood- pecker Colaptes campestris ( Vieillot ). Larger galls also were more frequently attacked by the fungus Penicillium sp. Gall attack rates were correlated with S. lycocarpum stem mortality ( 43.4% of plants analyzed), because galls could act as nutrient sinks or favor the breaking of stems. The possible effect of C. clitellae on the population dynamics of S. lycocarpum is discussed. KEY WORDS Collabismus clitellae, Coleoptera, Solanaceae, plant-insect interactions , gall mor- tality GALL-INDUCING INSECTS are extremely diverse and have interesting and complex life histories. Most of their life is spent embedded within tissues of their host plants, with which they have perhaps the most intimate re- lationship of all organisms ( Mani 1964 , Mattson et al. 1988, Fernandes 1990). The understanding of the nat- ural history of Neotropical galling insects is tremen- dously poor, most studies having centered on the eco- logical aspects of gall distribution ( Fernandes et al. 1988; Fernandes and Price 1988, 1991). In addition, there are few studies on the frequency and kind of impacts caused by galling insects on their host plants, especially for shoot galls (Sacchi et al. 1988). The weevil Collabismus clitellae Boheman forms galls on shoots of the lobeira tree, Solanum lycocarpum St. Hil. (a synonym of S. grandiflorum RandP. variety 1Carvalho 19851) (Solanaceae), a woody shrub that grows to a height of 3 m. This plant is a common weed in central and southeastern Brazil , occurring along high- ways, pasture, grasslands , and disturbed areas (Carvalho 1985 ). This association also was recorded for S . grandi- florum in Minas Gerais State ( Bondar 1923, Lima 1956). Here we describe the phenology, general charac- teristics , and mortality factors acting upon C. clitellae in a population of S. lycocarpum in southeastern Brazil. We also provide data on the distribution of galls within I Departamento de Zoologia, IB, Universidade Estadual de Campi- nas, C. P. 6109, CEP 13083 - 970, Campinas, SP, Brasil. 2 Departamento de Biologia Gera] , ICB, Universidade Federal de Minas Gerais , C.P. 486, CEP 30161-970, Belo Horizonte , MG, Brasil, and between plants and discuss some aspects of the impact of these galls on the host plant. Materials and Methods The study was conducted between May 1991 and July 1992 in a population of S. lycocarpum located along highway MG-010 (km 89), near Serra do Cip6, Minas Gerais, 840 m above sea level. The dominant vegetation is cerrado, which is regularly cut as a man- agement practice for cow grazing. Plants of S. lyco- carpum were cut at 5 cm above the ground every other year, and were last pruned in January 1990. The pop- ulation studied consisted of clones with several ramets patchily distributed. Ramets were 16-18 mo old and varied from single small shoots (<10 cm from the ground) to 1.6 m high. Ramets up to 3 m high also were found and examined in the study area. We randomly collected 385 galls from 97 individuals of S. lycocarpum. To identify possible patterns of gall distribution within and between plants, we measured plant height and gall height on the plant relative to the ground. Because plant height was variable, the distri- bution of galls on different plant parts was analyzed using the gall height/plant height ratio. The distribu- tion on the plants was then measured by dividing gall locations into basal (0-0.33), median (0.33-0.66), and apical (0.66-1.00) parts of the plant. We also recorded the diameter of the galled stems and whether they were wilting or dead, to evaluate the impact of galls on stem survival, using the gall attack rates ( see below). 0013-8746/98/0404-0409$02. 00/0 © 1998 Entomological Society of America