SIE JOHN LUBBOCK ON THE ANATOMY OF ANTS. 145 



The medifurca (PI. XI. fig. 2 ; PL XII. fig. 5, Med) rises from the medipectus. It is 

 much more elongated and slender than the antcfurca, and has the form of a Y, the upper 

 arms of which, however, are connected by a cross bar, thus leaving a triangular orifice 

 with rounded angles, through which runs the nervous chord. To a process of the cross 

 har is attached the muscle which elevates the prothorax. 



The postfurca (PI. XL fig. 2 and PL XII. fig. 6) also has somewhat the form of 

 a Y. The stem, however, is much shorter, the branches are curved, and the cross bar 

 is absent. The postfurca arches forwards, so that the upper part of the arms approach 

 those of the medifurca, with which they are connected by tendinous fibres. Between 

 the medifurca and the postfurca lies the third thoracic ganglia. 



Muscles of the Mead. 



There are two elevators of the head on each side (a & a 1 ). The first (PL XL figs. 

 1, 2, & 5, a) is a thin muscle, which rises from the back near the middle line, at the 

 junction of the pro- and mesothorax, and, passing forwards, is inserted at the upper margin 

 of the occipital foramen, where the posterior margin of the head joins the intersegmental 

 membrane. The second is more powerful. It (PI. XL figs. 1, 2, a 1 ) rises from the anterior 

 surface of the upper part of the antefurca, and, passing forwards and slightly upwards, is 

 inserted close to the preceding. The heads of attachment of this muscle reach almost 

 across the segment. 



The first depressor of the head (PI. XL figs. 1, 2, b), like the second elevator, is attached 

 to the anterior face of the antefurca, but at a lower level, and, passing over the prothoracic 

 ganglion, is attached to the inferior margin of the occipital foramen. 



The second depressor of the head (PL XL fig. 1, PL XII. fig. 1, b x ) is attached to the 

 central and hinder part of the propectus, and, passing directly forwards, is also attached 

 co the lower edge of the occipital foramen. 



The rotators of the head are five in number on each side. The first (PL XL figs. 1, 2, & 



t,c) rises from the middle of the lateral wall of the pronotum, and, passing downwards 



ind inwards, is attached to the anterior toothed process of the propectus. The second 



'otator passes from the middle of the lateral wall of the propectus (PL XL figs. 4, 6, &7, c l ), 



md is attached to the outer anterior toothed process of the prosternum. The third 



■otator (PL XL figs. 4, 6, 7, c' 2 ) lies rather nearer the middle of the segment. In front it 



s attached to the inner toothed process, and posteriorly to the lateral and posterior 



vail of the propectus, a little behind the preceding. The fourth rotator (PL XL 



igs. 1, 2, 6, d) commences at the anterior process of the propectus, close to the preceding, 



md, passing backwards and slightly inwards, is attached to the anterior central process 



>f the antefurca. The fifth rotator (PL XL figs. 1, 2, & 6, d l ), rises with the preceding, 



mt passes diagonally across the segment to be attached to the lateral edge of the antefurca. 



Although the muscles of the head of Coleoptera, as described by Straus-Durckheim in 



Melolontha, and as given generally by Burmeister in his ' Handbook of Entomology,' are 



aore complex than those which are found in Ants, yet neither of these authors describe 



ny muscle exactly comparable to the following. 



This muscle (PL XL figs. 1, 5, e) differs from the preceding in that, while they taper 



