A lepidopterous pest complex, collectively referred to as "langosta" by subsistence farmers, is an important constraint to sorghum and maize production in southern Honduras. The objectives of this study were to identify the insect species in the langosta complex, determine their population density and their relationships to crop and non-crop vegetation. Relative and destructive whole plant samples were taken on intercropped sorghum and maize from May to August in plots managed using farmer's technology and farmer's technology plus weed control in 1988 and 1989. Weed identity and density were recorded. Spodoptera frugiperda (J. E. Smith), S. latifascia (Walker), Metaponpneumata rogenhoferi (Moschler), and Mocis latipes (Guenee) larvae were identified as the principal insect species in the langosta complex. The fall armyworm, S. frugiperda, was the predominant species collected throughout the study period. Spodoptera latifascia and M. rogenhoferi were present only early in the season. Populations of S. frugiperda on the crops were higher in plots without weeds; Spodoptera latisfacia and M. rogenhoferi populations did not appear to be influenced by non-crop vegetation in the treatment plots, but were influenced by vegetation adjacent to plots where they fed prior to planting. The grass looper, M. latipes, was present in mid-season and populations on sorghum and maize were higher in plots without weed control.