é OF SUCTION IN LYGUS PABULINUS. (Alii 
(text-fig. 6), which are spread at their other ends over a large part 
of the posterior wall of the head. 
The retractors of the mandibles consist of two groups which 
pass above and below the optic nerve (text-tig. 5). 
(5) The Maxillo-mandibular Muscles. (Text-figs. 20, 21, Mx. 
Md.M.) 
These run from the mandibular levers to the levers of the 
maxillary stylets on either side. It will be remembered that the 
mandibles and the maxillary stylets do not lie at the same level, 
one being above the other, and at the same time the maxillary 
stylets project further back into the head than the mandibles. In 
the normal position the tips of the mandibles and the maxillary 
stylets are level, and in this position they are thrust into the 
plant-tissue. 
When these muscles contract, they pull in the mandibles and 
push forward the maxillary stylets a little. Thus there is no 
hindrance to suction by the maxille, as they are free from the 
mandibles. At the same time the mandibles get themselves fixed 
into the cellular walls by means of their recurved hooks and thus 
steady the maxille for suction, as the latter are firmly attached 
to the former by the interlocking device. Thus these muscles 
play a useful part in the mechanism of suction. 
(6) Zhe Antagonistic Muscles. (‘Text-figs. 5, 6, 20, A.M.) 
These muscles are attached to the mandibular levers at one end 
and to the postero-dorsal wall of the head at the other. They are 
ealled antagonistic because they oppose the protractors of the 
mandibles in their action, inasmuch as they bring the levers 
back to their normal positions. They are very important, as there 
is no other device to effect this readjustment. 
They have nothing to do with the pharynx, as Bugnion and 
Popoff (4) seem to think, who describe these muscles as ‘ Antagon- 
istique ou Abaisseur du Pharynx.” The description that they 
are attached to “une lame horizontale rattachée au Pharynx par 
une expansion,” is absolutely inaccurate. This horizontal blade 
(lame) is nothing but the mandibular lever, which has nothing 
to do with the pharynx, but which is attached to the mandible. 
‘Ta lame horizontale tendant a effectuer un mouvement de bascule, 
Veffet de l’antagoniste doit étre d’abaisser le pharynx ou tout au 
moins de le maintenir en place au moment oti le dilatateur entre 
en action.” “La fonction du muscle antagoniste est de maintenir 
Yappareil en place.” With due respect to these authors, I think 
that their description is absolutely beside the mark. These 
muscles have nothing to do with the pharynx. Wedde, however, 
holds that there is no need for such antagonistic muscles of 
Bugnion. He says, “‘ Antagoniste fiir die Schlundmuskulature 
sind nicht vorhanden, es wirken als solche die héchst elastichen 
chitinteile des Pharynx selbst.” 
49* 
