For the code below the labels are at the base of each arc, I need them to be in the center.
\documentclass{article}
\usepackage[utf8]{inputenc}
\usepackage{tikz}
\usetikzlibrary{shapes,positioning}
\begin{document}
\tikzset{ell/.style={ellipse,draw,minimum height=0.15cm,minimum width=0.2cm,inner sep=0.1cm}}
\begin{figure}[t]
\begin{center}
\begin{tikzpicture}[>=stealth]
\node[ell] (e1)at (-3,0) {\color{blue}$1$};
\node[ell] (e2)at (3,0) {\color{blue}$2$};
\draw (-2,-1)--(-1,-1.5)--(-1.5,-2)--cycle;
\draw (2,-1)--(1.5,-2)--(1,-1.5)--cycle;
\node[ell] (e6)at (0,-3) {\color{blue}$6$};
\draw[<-](e1)--(-2,-1) node[left]{\color{red} \tiny $y_{11}$};
\draw[<-](e2)--(2,-1) node[right]{\color{red} \tiny $y_{21}$};
\draw[<-](-1.25,-1.75)--(e6) node[left]{\color{red} \tiny $y_{12}$};
\draw[<-](1.25,-1.75)--(e6) node[right]{\color{red} \tiny $y_{22}$};
\end{tikzpicture}
\end{center}
\end{figure}
\end{document}
shapes.geometric
library) where you can use some options in a tikzset (minimum height, minimum width, rotate, etc.) so that you could address directly your arrows to these nodes instead of computing their coordinates.