Melon Pest - Darkling Beetles
Content from UC IPM: http://www.ipm.ucdavis.edu/
DESCRIPTION OF THE PESTS
Darkling beetle adults are from 0.13 to 0.25 inch long (3 to 6 mm) and vary from black or bluish black to rusty brown. Do not confuse darkling beetles (Tenebrionidae) with predatory ground beetles (Carabidae), which prey on various soil dwelling pests. Darkling beetles generally have clubbed antennae whereas carabids do not. Darkling beetles may be hidden by dust or a thin layer of soil. Larvae are cylindrical, wirewormlike, soil-inhabiting worms that are light yellow to dark brown and range from 0.03 to 0.33 inch (1–8 mm) in length. They are often referred to as false wireworms.
Darkling beetles are generally not a problem unless large populations build up when the plants are in the seedling stage. Young plants may be girdled or cut off at or below the soil surface. After the plants reach a height of 5 to 6 inches, darkling beetles are usually not a problem. However, further feeding may occur on flower blossoms during bloom, on the undersides of leaves, and on the netting of mature melons. They can also bore into fruit where it rests on the ground.