Compounds, extractable from natural products, which can be divided into two groups; one based on compounds containing glycerol--the phosphoglycerides, and the other on compounds containing sphingosine--the phosphosphingo-lipids. The comparative study of the phospholipids present in six orders of insect made by Fast has been extended to include an example from the primitive order Thysanura and also the Isoptera. A number of surveys of the phospholipid content and type have been made covering the lifetime of the insect from egg to adult. These include studies made on Tribolium confusum, Phormia reqina, Ceratitis capitata, Dacus oleae, Lucilia cuprina, Anthonomus qrandis, Culex pipiens fatiqans, Acheta domesticus, Vitula edmundsae serratilineela, Trogoderma granarium, Diatraea grandiosella. Where a particular tissue has been isolated from various insects and the phospholipid types present in the lipid extract of it determined, there have been few results to suggest that the phospholipid pattern of the tissue differs greatly from that of the whole insect.