460 WESTWOOD ON THE 



these three segments he traced four distinct pieces — a praescu- 

 tum, scutum, scutellum, and postscutelhim. Now according to 

 these views, (the great value of which has been acknowledged 

 by the most philosophical of our own zoologists, Mr. MacLeay,) 

 that part of the thorax which in coleopterous insects has been 

 generally termed the scutellum, is considered as the scutellum 

 of the mesothorax. In this order it is generally present, of a 

 small or but moderate size, and of a triangular form ; its 

 greatest development being in the genus named from this cir- 

 cumstance Macraspis by Mr. MacLeay, in which it is often 

 half the size of one of the elytra ; but in order to support the 

 enlargement noticed in this genus, I have observed that the 

 dorsum of the metathorax is also produced into a larger trian- 

 gular plate, with an impression on its upper surface, to receive 

 the mesothoracic scutellum. In some beetles, as in the genus 

 of Lamellicorns, named from this circumstance Gi/mnetis as well 

 as Macronata, Lomaptera and Agestrata Esch, — {Tetrac/onos, 

 Gory and Pei'ch,) the scutellum, although present, is concealed 

 by the prothoracic shield, which is produced over it in the shape 

 of a triangular lobe. In the former of these genera, however, 

 the mesothoracic scutum is so completely united with the scu- 

 tellum, that no trace can be perceived of their distinction. In 

 some other beetles there appears to be no visible scutellum at the 

 base of the elytral suture, as in the Coprides and other Scarabaei 

 exscutellati ; but upon removing the prothorax, the scutellum 

 will be found much more distinct from the scutum than even 

 in the Cetonies and Gymnetes; it is, indeed, present at the 

 base of the elytra, but from their peculiar form it is become 

 perpendicular instead of horizontal. Fabricius states, that 

 " insecta quee elytra connata gerunt, nullo gaudent scutello." 

 This is not the case; Platysma niger, e.g. having a very visible 

 scutellum. Messrs. Kirby and Spence state, that " in Melo'c 

 there really seems to be no scutellum." This is also incorrect; 

 the scutellum, although concealed, being very broad, of a 

 bright blue colour, and covering the upper side of the meta- 

 thorax, which is very slightly developed. 



In the Heteroptera {Clmex, Nutonecta et Nepa^ Lin.) the 

 same general formation of the prothorax and mesothoracic 

 scutellum exists, but occasionally the latter is of so large a 

 size that the entire abdomen and wings are completely covered. 

 This occurs in the genus named from this circumstance 



