82 EXPLANATION OF TERMS 



Mesepimeron: in Odonata; the sclerite between humeral and first lateral 



suture. 

 Mesepisterna: in Odonata; the oblique lateral pieces of mesothorax, meeting 



dorsally in a ridge. 

 Mesially: at or to the middle. 

 Mesinfraepisternum: a sclerite formed between propleuron, mesepisternum, 



mesepimeron and second coxa. 



Meso: middle: as prefix, drops the o when stem begins with a vowel. 

 Mesoblast: the middle germ layer of the embryo: mesoderm. 

 Mesoderm: = mesoblast ; gives rise to muscular and circulatory systems. 

 Mesodont: := amphiodont ; q. v. 



Mesomeros: the 2d to 5th abdominal segments in Lepidoptcra. 

 Meson: the middle plane of the body. 



Mesonotum: the primitively upper surface of the 2d or middle thoracic ring. 

 Mesophragma: an internal prolongation of the metaprsescutum, affording 



attachment to some of the wing muscles. 

 Mesopleura: in Diptcra, the space before the root of the wing between the 



dor so- and sternopleural sutures : in Hymcnoptera, the piece below the 



insertion of the wings. 

 Mesopleural bristles: in Diptcra, are inserted in the angle formed by the 



dorsopleural and mesopleural sutures. 

 Mesopleural suture: in Diptcra, runs from the root of the wings downward 



and separates the mesopleura from the pteropleura. 

 Mesopleuron: the lateral surface of the mesothorax. 

 Mesosternal cavity: in Elatcridcc, the opening into which the prosternal 



spine or mucro is fitted. 

 Mesosternal epimera: in Cole opt era; the narrow pieces separating the meso- 



sternal from the metasternal episterna. 

 Mesosternal episterna: Coleoptcra; on each side of mesosternum between 



anterior border and epimera ; generally separated by a distinct suture. 

 Mesosternal lobes: in Orthoptcra; = mesosternellum ; q. v. 

 Mesosternellum: in Orthoptcra, two median lobes of the mesosternum, one 



on each side of the deep median notch : in general, the sternellum of the 



mesothorax. 



Mesosternum: the underside or breast of the mesothorax. 

 Mesostethidium: = mesothorax; q. v. 

 Mesostethium: the middle piece of the underside of metathorax, between 



the middle and hind legs. 



Mesostigma: in Odonata, the spiracles of second thoracic segment. 

 Mesosulcus: a central longitudinal furrow of mesosternum in Hymcnoptera. 

 Mesotarsus: the tarsus of the middle leg. 

 Mesothoracotheca: the pupal covering of the mesothorax. 

 Mesothorax: the second or middle thoracic ring; bears the middle legs and 



the anterior wings. 

 Mesotergum: =mesonotum; q. v. 

 Meta-: posterior: used as a prefix to designate the third thoracic ring and 



its parts. 



