Entomology definition of First longitudinal vein September 8, 2014 Raj Entomology Dictionary 0 Please Like Us!!! DesiGoogly.com > Education News > Entomology Dictionary > Entomology definition of First longitudinal vein Entomology definition of First longitudinal vein: in Diptera; – radius 1 (Comst.). Entomology First longitudinal vein definitionFirst longitudinal vein Entomology explanationFirst longitudinal vein Entomology meaningReviews & Comments