4. Types of various spinnerets. _a_, simple orifices (_Mytilaspis_); _b_, double orifice (_Planchonia_); _c_, multilocular orifice (_Ctenochiton_); _d_, multilocular orifice (_Cœlostoma_); _e_, simple protruding spinneret (_Aspidiotus_); _f_, serrated protruding spinneret (_Mytilaspis drimydis_); _g_, protruding spinneret (_Acanthococcus_); _k_, conical spiny spinneret and cottony secretion (_Rhizococcus_); _m_, lanceolate spinneret and glassy secretion (_Inglisia_); _n_, group of abdominal spinnerets, with detached orifices (_Mytilaspis_); _p_, double multilocular orifice (_Cœlostoma_); _s_, coronetted spinnerets and part of glassy secretion (_Icerya_). 5. Rostra. _a_, simple rostrum of Diaspidinæ; _b_, rostrum and trimerous mentum of Coccidinæ. 6. Foot of a female insect. _c_, coxa; _tr_, trochanter; _f_, femur; _ti_, tibia; _ta_, tarsus; _cl_, claw. 7. Foot of a male insect. The letters as in Fig. 6. 8. Foot with digitules, upper and lower. 9. Type of female antenna (_Ctenochiton_). 10. Type of female antenna (_Dactylopius_). 11. Type of antenna of larva (_Icerya_). 12. Type of male antenna (_Fiorinia_). 13. One joint of antenna of Monophlebidæ (_Icerya_). 14. Diagram of head of male of Lecanidinæ (after Signoret), both dorsal and ventral aspects being shown together. _a_, antennæ; _e_, _e_, true eyes, the lower pair being on the ventral surface in the place of the mouth; _oc_, _oc_, ocelli. 15. Head of male Icerya, with facetted eyes. 16. Wing of male insect. _n_, nervure. [Illustration: PLATE I.] Plate II. Fig. 1. Types of anogenital rings. _a_, Diaspidinæ; _b_, Lecanidinæ; _c_, Acanthococcidæ; _d_, Dactylopidæ; _e_, Monophlebidæ. 2. Types of last abdominal segments of female. _a_, Diaspidinæ; _b_, Lecanidinæ; _c_, Acanthococcidæ; _d_, Dactylopidæ; _e_, Monophlebidæ. 3. Types of last abdominal segments of male, and sheath of the penis. _a_, Diaspidinæ; _b_, Lecanidinæ (_Ctenochiton_); _c_, Acanthococcidæ; _d_, Lecanidinæ (_Inglisia_); _e_, Dactylopidæ; _f_, Monophlebidæ (_Icerya_). 4. Respiratory system. _a_, spiracle of _Lecanium_ (after Targioni); _b_, spiracle of _Coccus_ (after Targioni); _c_, diagram of arrangement of the four spiracles and the tracheal tubes (Lecanidinæ) (s. spiracles); _d_, spiracle and trachea of Cœlostoma. 5. Types of spines and hairs. _a_, anal serrated hairs (_Aspidiotus nerii_); _b_, spiracular spines (_Ctenochiton_); _c_, marginal spines (_Ctenochiton_); _d_, lanceolate marginal spines (_Inglisia_); _e_, spines on anal tubercles (_Rhizococcus_); _f_, marginal spines (_Eriococcus_); _g_, conical spines (_Eriococcus_); _k_, marginal hairs (_Dactylopius_); _m_, hairs (_Icerya_); _n_, anal hairs (_Cœlostoma_). [Illustration: PLATE II.]