144 SIE JOHN LUBBOCK ON THE ANATOMY OF ANTS. 



The posterior surface of the propectus is connected with the anterior edge of the meso- 

 pectus hy a tough, hut flexible, membrane. 



I have found it difficult to understand the descriptions given of the interior skeleton 

 of the thorax hy previous writers, nor do their figures give much assistance. In the 

 normal insect-thorax there appear to he seven principal processes — four springing from 

 the back, and called by Kirby and Spence the phragma, prophragma, mesophragrna, and 

 metaphragma ; and three from the sternum, named by the same authors profurca, 

 mesofurca, and postfurca. In the worker Ants the four superior processes are not 

 developed, but the furca, mesofurca, and postfurca are very important ; they give 

 attachment to various muscles, and serve also to protect the nervous system. Kirby and 

 Spence, however, dismiss them very summarily, and, as regards the processes of the endo- 

 sternum, state that they "are not sufficiently remarkable to require particular notice " *. 

 Burmeisterf says that in the prothorax (of the Hymenoptera) "there are two strong 

 pointed processes, each of which has a double root. The exterior one comes from the 

 margin of the prosternum, and the interior one from the central ridge of the same part. 

 Between these roots the muscles of the coxae pass, and between the processes themselves 

 run the pharynx and the nervous cord ; and it is to these processes that the connecting 

 muscles of the pronotum and prosternum are attached. In the mesothorax we first rind 

 the prophragma, a small, not very high, horny partition, which descends from the anterior 

 margin of the mesonotum ; and we next find a delicate ridge, which encompasses the 

 whole distinctly separated mesonotum. The mesosternum and scapuke are closely joined 

 in a half-ring, and from the central carina of this ring springs a broad strong ledge, which 

 at its upper margin is furnished on each side with a strong process ; they form with the 

 ledge a rectangular cross, and serve as points of insertion for the muscles of the coxa- of 

 the middle legs, lying on each side contiguously to the central ridge." As regards the 

 metafurca, all he tells us is, " between the metanotum and metaphragma the two large side 

 pieces and their auxiliaries lie, separated from each other by furrows, from which, inter- 

 nally, strong ridges spring, and to which the muscles of the posterior legs are attached." 



Graber, in his admirable ' Die Insekten,' truly observes that the endoskeleton has been 

 almost entirely neglected by recent entomological writers. I trust, however, that the fol- 

 lowing description and the accompanying figures may give some idea of the endoskeleton 

 as it exists in the workers of Lasiusjlaciis. 



The hinder plate of the propectus turns upwards at approximately a right angle, and 

 is produced into the antefurca (PI. XI. figs. 1, 2, 5, & 6; PI. XII. fig. 8), a chitinous pro- 

 cess which extends more than halfway up the dorsum, leaving, however, a central orifice 

 (PL XII. fig. 4) through which the nervous chords penetrate, while the oesophagus and 

 the heart pass between the upper edge of the antefurca and the dorsum. 



As seen from behind (PI. XII. fig. 4) it has the form of a cross with four arms. In the 

 middle of the centre piece is an oval orifice, the wider end below, through which the 

 nervous system passes. The centre of the upper part sends out a process both anteriorly 

 and posteriorly, as shown in PL XL fig. 2 ; in fact it forms a sort of case for the protection 

 of the ganglia. 



• ' Introduction to Entomology,' vol. iii. p. 587. t Op. cit. 



