296 Annals of the South African Museum. 



NOTES ox Giebelia and Mackayia. 



Having all the known forms of these peculiar parasites before us, 

 we have drawn up the following tables for their differentiation. 



Key to Genera. 



The sexes with similar simple antennae which are carried gently recurved. Anterior 

 edge of trabecula, measured from the apex to the hair at the junction with the 

 edge of the head, distinctly longer than the 1st antennal joint . . Giebelia. 



The sexes with dissimilar antennae which are carried in the <? bent sharply 

 back. One or more joints with an appendage. Basal joint ( <f ) with a distinct 

 fovea on upper surface, edge of trabecula markedly less than length of 1st antennal 

 joint (| to J) .......................... 



to Species of GIEBELIIDAE. 

 (For the more convenient handling of the ? ? we treat all the species together). 



3 S . 

 A. Antennae simple. 



a. Six peg-like spines on head, 1 on each side of signature, 1 on an extension of 

 the antennal band above the 1st antennal joint and 1 at the end of another band 

 which curves inwards from the base of the antennae. (We may refer to these 

 3 parts as "anterior," "lateral," and "posterior" respectively.) Paramera 

 straight with parallel sides. Basal plate narrow .. .. Gibelia hexakon, n. sp. 



l>. Four peg-like spines, 2 anterior, 2 posterior, the lateral pair represented by 

 minute spines. Paramera distinctly curved. Sides not parallel, there being 

 a sudden concavity on the inner edge near the base. Basal plate short and 

 broad .......................... Giebelia mirdbilis. 



AAj. Antennae with appendages. 



a'. Antennae with 1 appendage on 3rd joint. Anterior edge cf trabecula . 1st 

 antennal joint. Spines as in G. mirabilis 3 , eye prominent and round. Para- 

 mera short, broad, and once curved .......... Mackayia dimorpha. 



b' . Antennae with appendages on 1st and 3rd joints. Anterior edge of trabe- 

 cula 1st antennal joint, anterior spines bristle-like, eye not prominent, paramera 

 twice bent .................... Mackayia heteracanthus. 



22. In describing M. dimorpha and M. heteracanthus ? ? we 

 have mentioned that the transverse band between the antennals, 

 which is so conspicuous a feature of the $ $ forehead, is inter- 

 rupted near the signature. In both $ J of the Giebelia spp. this 

 band is conspicuous though uncoloured and very narrow on either 

 side of the apex of the signature. By this feature we find it very 

 easy to separate the 2 2 actually before us. We do not care to use 

 this character, however, in the following table, as on recurring to 

 our 5? 2 Mackayia we find that there are membranous creases 



