THE MUSCULAR SYSTEM. 255 



former originates from the centre of the mentum, and passes to its 

 inner margin, and inserts itself at the exterior margin of the joint. 

 The succeeding joints have a similar structure to those of the max- 

 illary palpi. 



173. 



The antennae have three muscles which move them an extensor, 

 which originates from the forehead in front of the eyes, and affixes 

 itself to the exterior margin of the basal joint ; a flexor, which ori- 

 ginates from the anterior apex of the inside of the skull, and affixes 

 itself to the inner margin of the basal joint ; and an elevator, which 

 originates exteriorly contiguous to the extensor from the margin of the 

 eye, and inserts itself at the lower margin of the basal joint. 



The individual joints have each two muscles, namely, those known 

 from their situation as extensor and flexor. 



Besides the above-named muscles there are other smaller ones, 

 which retain the pharynx and palate in their proper place. In Locusta 

 the muscles of the lips and tongue participate in this ; in the Coleo- 

 ptera they originate from the inside of the skull, and insert themselves 

 at the pharynx, or from the forehead itself when the processes of the 

 head do not advance so far. In Dyticus, from the skull of which two 

 long, bent, horny processes originate, which extend as far as the fore- 

 head, and enclose the pharynx between them, they originate from the 

 inner margin of these processes. In Melolontha, in which this internal 

 frame of the head is smaller, two come from the forehead itself, and 

 two others, smaller, on each side, from the clypeus : it is the same in 

 Locusta and Gryllus. 



174. 



In insects with haustellate oral organs the muscles of the mouth are 

 much smaller. The Hymenoptera display the greatest conformity, 

 particularly as they have large mandibles, and we can even recognise 

 in their maxillae analogous muscles. The entire suctorial apparatus, 

 namely, the proboscis, with the maxillae, palpi, and labium. has a 

 moveable basis, formed of several united bony pieces, which, by means 

 of a soft but tense membrane, stand in connection with the margin of 

 the large oral aperture of the head. According to Treviranus * there 

 lie in this membrane one simple and four double horny bones. The 



* Vermischte Schriften, vol. ii. p. 117, PI. XIII. f- 1. 



