Expression of IRS-2 is up-regulated after tick attachment to the host. IRS-2 transcripts accumulate rapidly in salivary glands after the attachment of an adult I ricinus female, less rapidly in its ovaries, and they remain almost unchanged in its midgut. Each bar in the graph represents the ratio between IRS-2 transcript abundance in a certain tick tissue and a given tick feeding stage, compared with the corresponding tissue from unfed ticks (ie, the black bar in the salivary glands part of the graph shows that the transcript abundance of IRS-2 mRNA is 20× higher in the salivary glands of fully fed adult female ticks than in the salivary glands of unfed females). The scale in the y-axis is logarithmic.