There's a longstanding confusion in the etymological origin of the word locust. Locust is both a bean from the carob plant and an insect. The Greek word for cakes or bread made from the flour of the carob bean is 'egkrides' and the Greek word for locust the insect is 'akrides'. The insect locust is approved to be clean for consumption in Leviticus. It was a delicacy in those days and was mostly consumed by the upper and/or priestly class.
John the Baptist belonged to a group of ascetics who believed in repentance and in leading an austere lifestyle. The carob bean was seen as the diet of the lower class who normally endured hardship and exploitation from the priestly class. So most likely John the Baptist ate locust plant seed from the carob tree.
Also, regarding honey, it could be anything from saps of certain trees to juice of the crushed dates. Carob flour and crushed dates made a good damper or sweet rustic cake, hence the word 'egkrides' in the Greek version of the Bible.
Some Church Fathers circa 400AD put forth an injunction to change the word 'egkrides' in the Bible meaning cakes to 'akrides' the insect locust, not realising that locust the insect was a delicacy enjoyed by the priestly upper crust, from whom John the Baptist and people like John distanced themselves from.
