Still higher homologues of terpenes are found in insects, presumably made by extending the synthesis scheme already described. The sester-terpenes, C25 compounds, contain five isoprene units. Acyclic sesterter-penes and C30 compounds, of unknown function, with structures similar to springene have been found in Dufour glands of stingless bees, and geranylfarnesol was identified in the frontal glands of Reticulitermes santonensis, and as esters in the wax of scale insects.

A group of homopterous scale insects make insect wax that is an article of commerce (Plate 8). In China the insects are Ericerus pela, and in India Gascardia cerifrea, while in Central and South America various Ceroplastes species provide the same product. These waxes consist principally of esters of long chain acids with long chain alcohols, but hydrolysis of Ceroplastes albolineatus wax gives geranylfarnesol (Figure 7.4) and the cyclized derivatives of it, albolineol, ceroplastols I and II, and ceroplasteric acid and albolic acid (Figure 7.4). The mechanism shown is how they are probably formed, though no studies have been made.

Figure 7.4 Sesterterpenes from Ceroplastes albolineatus, homopteran scale insects. The mechanism of formation is only conjecture
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