Aristobia reticulator (Voet) is reported for the first time in India as a stem borer of litchi trees, Litchi chinensis Sonn. (Sapindaceae) in the State of Arunachal Pradesh. Beetles were observed feeding on bark, thereby girdling stems, branches, and soft twigs, while larvae tunneled inside the stem. Of 382 trees examined in the survey, 88.5% were damaged by this pest. The grubs caused maximum damage in saplings and branches. The beetles emerged during June–August from stems by making an exit hole, and thereafter they fed on the bark of tender branches. After pre-mating and pre-oviposition periods of 4.8 and 7.5 days, respectively, females cut a slit into the bark and laid eggs under it. Incubation period ranged from 15 to 26 days. Newly hatched larvae first started feeding subcortically and then entered the sapwood. Larvae continued to move down the branches, feeding and ejecting frass from their tunnels. The mature larva formed a pupal cell under the bark. The mean larval and pupal periods ranged 260–288 (mean = 274.5) and 32–42 (mean = 38.4) days, respectively. Beetles emerged from the pupal cell by cutting a circular exit hole. Adult males survived longer than females. Females laid 16–43 eggs during an oviposition period of 25–42 days. The beetle has a life cycle of approximately one year. In host preference studies, A. reticulator laid eggs on litchi and guava only, although beetles were also found to feed on the bark of Cajanus cajan (L.) Huth (Fabaceae), but larval development was not observed.