EXTERNAL ANATOMY OF INSECTS. 689 



up so as to defend the sides and part of the back of the 

 abdomen ; in Morpho Teucer it turns down, and meeting 

 that of the opposite wing, forms a semitube which re- 

 ceives and shelters that part below. In the Crepuscular 

 and Nocturnal Lepidoptera this fold, especially in the 

 former, is very slight. With respect to semifolds in the 

 Diurnal, there is one originating in the disk, between each 

 of the nervures, that goes to the margin of the wing; like- 

 wise the under wings, particularly of many Noctuce, Arc- 

 tiee, &c, have many longitudinal semifolds. 



In the Neuroptera Order several variations take place 

 with regard to the position of these organs in repose : 

 thus, in JEshna, Libellula, &c, they continue expand- 

 ed ; in Argion they are applied to the body ; in Myrme- 

 leon the upper are horizontally incumbent on the lower ; 

 in Hemerobius they incline to the horizon. With regard 

 to their folds in JEshna, &c, the longitudinal nervures 

 alternately form the summit or the bottom of a semifold, 

 as do those branches that terminate in the posterior mar- 

 gin ; this kind of plicature may be observed, but in a less 

 degree, in Ascalaphus, Myrmeleon, &c. ; in Panorpa every 

 nervure is the ridge of a slight fold ; in Termes, on the 

 contrary, it forms its bottom. In the Trichoptera, the 

 under wing being much more ample than the upper, the 

 Anal Area forms a fold under the wing, and there seem 

 longitudinal secondary folds besides. 



We now come to the Hymenoptera. In this Order 

 the wings, as to their position in repose, are usually in- 

 cumbent upon each other, and cover the abdomen; in the 

 Vespida?, however, they are placed parallel to the body, 

 but do not cover it. Before I notice the plicature of 

 these wings, I must recall your attention to what I lately 



