Among the pests of cassava, the shoot fly, Neosilba perezi (Romero & Ruppell), is one of the most prevalent. It attacks mainly the terminal shoots and causes infested plants to produce lateral shoots. Reports on this species are rare or inexistent; thus, the purpose of this study was to assess three different areas for N. perezi infestation. The survey began in March 2008 and finished in February 2009. Fortnightly analyses were performed starting 45 days after planting, calculating the rate of infestation by N. perezi larvae in each study area. The areas were correlated separately for each parameter: fortnightly mean temperature, fortnightly mean rainfall, and plant age. The N. perezi larvae occurrence rate was higher in area 1 - which presented the highest population peaks in autumn and winter. There was only a single population peak in area 2, in winter; and area 3 presented the weakest population peak among the three, in November. The shoot fly population dynamics in the studied region is separately correlated to temperature, rainfall and plant age: temperatures above 23ºC, relatively high rainfall and older plants seem to have a negative effect on populations of this insect.

O valor médio da largura da cápsula cefálica de Alphitobius diaperinus foi verificado de acordo com seus estádios larvais, sendo medidos cinco indivíduos para cada estádio. O experimento foi conduzido em temperatura constante de 27ºC (± 0,1ºC). Os resultados obtidos mostraram que as larvas atingem oito estádios, com média de 0,228 mm (SD = 0,0192) para a larva recém-eclodida, até 1,339 mm (SD = 0,0436) no 8º estádio. Também foi observado que o fator de crescimento das larvas corresponde à regra de Dyar-Hutchinson, apresentando média de 1,29 para razões de crescimento ao longo do desenvolvimento. Esses dados poderão ser utilizados em estudos de fenologia e estruturação etária de populações de A. diaperinus no campo.

The mean width (n = 5) of the cephalic capsule instar of Alphitobius diaperinus was determined. The larvae were reared at 27ºC (± 0.1ºC). The result showed that A. diaperinus has eight larval instars. The head capsule of the 1st instar larvae measured x = 0.228 (SD = 0.0192) and the last instar larval measured x = 1.339 (SD = 0.0436). The developmental rate, determined by Dyar-Hutchinson's rule, was 1.29. These data may be useful for studies on phenology and age structure of A. diaperinus in the field.