One-dimensional strata of residueless meromorphic differentials

In projectivized strata of meromorphic $1$-forms on elliptic curves with only one zero, the locus of residueless differentials is a complex curve endowed with a canonical complex projective structure. Drawing on the multi-scale compactification of strata, we provide formulas to compute the genus of these curves and the degree of their natural forgetful map to ${\mathcal{M}}_{1,1}$. Additionally, we distinguish two non-hyperelliptic components in the residueless locus of the exceptional stratum ${\mathcal{H}}_1(12,-3,-3,-3,-3)$ and hence complete the classification of the connected components of these loci.