Possible Clues:

• Mills Brothers classic
• Mills Brothers song subject
• It's actually an insect
• Luminous insect
• Beetle with luminescent organs in the abdomen
• Beetle whose wingless females are partly luminous
• Beetle, partly luminous
• Beetle whose larva-like wingless females emit light
• Two wives run apart in darkness to find something luminous
• Bioluminescent beetle larva