For the most part, Transformers have always been divided into two factions: Autobots under the command of Optimus Prime, and Decepticons under the command of Megatron. While there have been several exceptions to this broad assertion over the more than 30 years of Transformers history, I would hazard a guess that the three characters featured today might be the first.
Pictured here are the Insecticons: Shrapnel, Bombshell, and Kickback (as seen left to right in all pictures in this entry). As they first appeared in the G1 cartoon, these three were a faction separate from Megatron and his Decepticons, and the two groups often found themselves at odds with each other. This state of affairs didn't last terribly long, as later cartoon episodes (to say nothing of independent continuities such as the one found in the Marvel Comics series) tended to show the Insecticons as a loyal Decepticon sub-group under Megatron's command, but at least at first, the Insecticons were fiercely independent of Megatron's troops.
The cartoon and the comic versions of the Insecticons also differed in regard to how the alternate modes for which the sub-group gets its name relate to real-world insects. In the cartoon, the Insecticons were giants, retaining their robot-mode size while changing forms. In the comic book, the Insecticons shrunk in size so that they might viably blend in with real insects, at least in proportion. No attempt was ever made to suggest that these black-and-purple creatures were non-mechanical in their insect forms (and any attempt to assign them to actual insect species will, at best, yield only a "close match"). Organic creature modes would have to wait until the Beast era.
There were other Insecticons that came out at about the same time as these three characters, called the "Deluxe Insecticons" for the simple reason that their toys were larger. Those toys were almost entirely absent from classic-era Transformers fiction, however, likely due to the fact that while the "main" three Insecticon toys were originally Diaclone molds (produced by Takara, the same as the majority of other early Transformers), the "Deluxe Insecticon" molds were owned by a rival company which competed with Takara in Japan, and thus the cartoon (which was used to promote the Transformers toys in both Japan and the US) avoided depicting them. Thus, whenever people talk about "the Insecticons" without further modifier or explanation, they're almost certainly talking about the trio seen here.