The cellular response to a heat shock treatment was originally observed in Drosophila by the appearance of specific puffs on polytene chromosomes (Ritossa 1962). These puffs are characterised by a high level of transcriptional activity. Concomitant with this physical manifestation is the strong induction of a restricted number of specific polypeptides thereby named Heat Shock Proteins (HSP). In Drosophila melanogaster, the major HSP were first identified through 35S-labelling experiments on Drosophila tissue culture cells and salivary glands (Tissieres et al. 1974) and have been commonly divided into three subfamilies based on their apparent molecular weight on SDS-PAGE. The Hsp83 and Hsp60 species are each sole members of their class, while many different genes encode for the highly conserved members of the Hsp70 subfamily. The small heat shock proteins (sHSP) group includes four polypeptides encoded by identified genes (hsp22, hsp23, hsp26 and hsp27) which are all found within the same locus on chromosome 3 (67B). However, additional genes carrying open reading frames (ORF) which could potentially encode for proteins carrying the α-crystallin domain, hallmark domain of the sHSP family, have been readily identified both within (hsp67a, hsp67b and hsp67c—formerly known as gene1, gene2 and gene3) and outside (l(2)efl) the 67B locus.