OF THE FAMILY COCCIDAE 15 



It is best developed in N. abietis (Text-fig. 4, B), where it stretches anteriorly from 

 behind the level of the posterior margin of the eyes to the anterior margin of the 

 head, but even in this case it is not joined to the ventral part of the midcranial 

 ridge (vmcr). The latter is usually well developed and Y-shaped. The median 

 part of the ridge merges posteriori}- into the ocular sclerite, but in some cases (/. 

 theobromae, Text-fig. 29, C ; the ERIOPELTIS group, Text-figs. 24, 26, 27, C) it 

 fades away before doing so and in Ceroplastodes chiton Green it is vestigial. The 

 lateral arms (lmcr) run to the base of each scape, but do not articulate with it. The 

 arms are long in some species (/. theobromae, Text-fig. 29, C), short in others 

 (Eriopeltis sp., Text-fig. 24, C), or even absent (E. Pfestucae, Text-fig. 26, C). The 

 area around the posterior section of the median part of the midcranial ridge is 

 usually membranous and weakly polygonally reticulated. Rarely, however, the 

 reticulation is entirely absent {Ctenochiton sp., Text-fig. 16, C ; Genus A, Text-tig. 

 20, C) or the area is both reticulated and sclerotized {Eriopeltis spp., P. myrtilli, 

 I. theobromae ; Text-figs. 24 & 26, 14, 12, 29 ; C). This area corresponds to the 

 ventromedial part of the epicranium of the more primitive margaroid Coccoidea, 

 where it is sclerotized. The ventral part of the midcranial ridge was described as 

 the " chitinous impression " by Pesson (1941), the " mesantennal plate " by 

 Borchsenius (1957) and the " sclerotized fork " by Bustshik & Saakjan-Baranova 

 (1962). The Russian workers suggested, quite erroneously, that it might represent 

 a rudiment of the mouth apparatus. 



The large ocular sclerite (ocs), dorsally separated from the median crest by a 

 membranous band surrounding the latter, constitutes most of the ventral and part 

 of the lateral surface of the head capsule ; ventrally it extends uninterrupted from 

 one side of the head to the other. It is distinctly polygonally reticulated. The 

 ocular sclerite is partly bounded anteriorly by the preocular ridge (procr), which 

 provides a process for articulation with the scape. In some species (the ERIO- 

 PELTIS group, Ctenochiton sp., E. pda, Genus A ; Text-figs. 24, 26, 27 and 16, 

 18, 20 ; C) it is fused with, or closely approximates its opposite number, where it 

 may also be joined by the median bar of the midcranial ridge. More often, however, 

 it fades away at some distance from the articulating process. 



The posterior margin of the ocular sclerite is bounded for the most part by the 

 well developed postocular ridge (pocr). Dorsally the ridge originates behind the 

 dorsal eye at about the level of the posterior margin of the median crest, passes 

 behind the ocellus and extends posteromedially across the lateroventral surface of 

 the head. Near the median line it curves backwards and extends for a short 

 distance beyond the anterior end of the proepisternum + cervical sclerite, either as 

 a definite ridge or as a small sclerite. In most species the ridge forks below the 

 ocellus, with the short anterior branch surrounding or partly surrounding the 

 ocellus. In the COCCUS group the postocular ridge is strong and thick through- 

 out, but in the other groups the dorsal part of it is weaker, uniformly thin or 

 gradually narrowing ; occasionally the part of the ridge immediately behind the 

 ocellus is missing or very weak (R. spiraeae, Genus A ; Text-figs. 9, 21). In the 

 literature the ridge has been illustrated, but not discussed by Leonardi (1920), 



