Table 1.

Studies investigating differences in DNA methylation patterns between queen and worker castes in social insects. (WGBS, whole-genome sequencing of bisulfite-treated DNA; MeDIP, methylated DNA immunoprecipitation-sequencing; MSRFLP, methylation-sensitive restriction fragment polymorphisms; RRBS, reduced representation bisulfite sequencing.)

	species	queens and workers strongly morphologically divergent?	differences found	kind of study	biological replication	reference	year
honeybees	Apis mellifera	yes	yes	bisulfite sequencing of a single gene, experimental manipulation	n/a	[43]	2008
	Apis mellifera	yes	yes	bioinformatic study of existing datasets. Genes that are differentially expressed between queens and workers show evidence of methylation over evolutionary time	four ‘caste specific’ genes showed differential methylation	[44]	2009
	Apis mellifera	yes	yes	WGBS of 50 pooled queen brains and 50 pooled worker brains	none at individual level	[45]	2010
	Apis mellifera	yes	no	WGBS and an array-based system	five adult queens and workers	[46]	2012
	Apis mellifera	yes	yes	WGBS of 96 pooled queen and 96 pooled worker larval heads	none at individual level	[36]	2012
	Apis mellifera	yes	no	MSRFLP	five each: adult and pupal queens and workers	[47]	2013
	Apis mellifera	yes	yes	MeDIP	nil at three ages	[48]	2013
	Apis mellifera	yes	yes	amplicon bisulfite sequencing of two genes	three sets of five brains from queens and workers	[49]	2017
	Apis mellifera	yes	yes	MeDIP	pools of 10 larvae, three queen and three worker	[50]	2017
	Apis mellifera	yes	no, but no direct comparison across castes	WGBS and RNA sequencing	two biological replicates and multiple tissues	[51]	2019
	Apis mellifera	yes	yes	WGBS of queen-destined and worker-destined larvae at three ages	tree replicate colonies but samples pooled across colonies	[52]	2020
bumblebee	Bombus impatiens	size only	no	MSRFLP	five each: adult and pupal queens and workers	[47]	2013
ants	Camponotus floridanus	yes	yes	WGBS of whole individuals	two biological replicates but queens and workers harvested from different colonies	[37]	2012
	Harpegnathos saltator	minimal	yes	WGBS of whole individuals	two biological replicates	[37]	2012
	Pogonomyrmex barbatus	yes	yes	MSRFLP	adult virgin queens (n = 9) versus workers (72)	[53]	2012
	Ooceraea biroi	no	no (between reproductive phases)	WGBS of adult brains	four replicates of pools of 20 brains	[54]	2016
	Dinoponera quadriceps	no	no (between gamergate and worker)	WGBS of adult brains	three biological replicates	[55,56]	2015
	Formica exsecta	yes	yes	RRBS	comparisons of 5–7 old and young workers and queens randomly selected from 19 colonies	[57]	2019
wasps	Dolichovespula maculata	size only	no	MSRFLP	five each: adult and pupal queens and workers	[47]	2013
	Polistes dominula	no	yes	MSRFLP	five each: adult and pupal queens and workers	[47]	2013
	Polistes canadensis	no	no	WGBS of adult brains	three biological replicates	[55,56]	2015
termites	Zootermopsis nevadensis	yes	yes	WGBS of male and female workers and alates	replicate individuals from a single colony	[33]	2016