A COMPARATIVE STUDY OF THE CUTICULAR STRUCTURE OF THREE FEMALE MEALY BUGS (HOMOPTERA: PSEUDOCOCCIDAE)

¹ Waite Agricultural Research Institute, University of Adelaide, Adelaide, Australia

1. The cuticular structure of three female pseudococcids, Pseudococcus adonidum L., Epicoccus sp., and E. acaciac (Maskell), has been investigated.

2. The cuticle of P. adonidum consists of a two-layered epicuticle, overlying a thin procuticle, almost all of which is endocuticle.

3. The cuticle of Epicoccus sp., is highly Specialized. Its epicuticle closely resembles that of P. adonidum. The dorsal cuticle is relatively thick, and is much modified chemically. Most of it consists of mesocuticle in which Millon's reagent delimits three well-defined zones which differ greatly in their reactions to stains and histochemical reagents. The endocuticle is much reduced. A thin layer of procuticle between the hypodermis and the endocuticle is impregnated with lipoid to from a "lipoid zone."

4. The cuticle of E. acaciae is thick. It differs from that of Epicoccus sp. principally in that there is no chemical zonation of the procuticle, and the lipoid zone s nielanin-pigmented.

5. Wax glands are numerous in the cuticle of P. adonidum. The contents of their reservoirs ("protowax") differ chemically from the surface wax. In Epioccus. many of the glands have atrophied; typical glands are confined to lateral parts of the cuticle in contact with the host plant, and these secrete large quantities of wax which fixes the insect permanently in position.

6. The specialized cuticle of Epicoccus appears to have evolved over a long period. during which the insects have been exposed to adverse environmental conditions.