458 PHYSIOLOGY. 



expanded, for instance, many flies, butterflies, Hymenoptera, and many 

 LibclluloE. In the latter, also, they remain in the same position during 

 repose that they are found in during flight ; the insect, therefore, does 

 not require to expand and direct them. Thence arises the facility with 

 which these creatures raise themselves into the air ; thence, also, as 

 well as from their lightness of structure and small size, the facility of 

 their motion in the air, and the long continuance of their flight. Beetles, 

 and especially the largest ones, have the greatest difficulties to overcome 

 in taking flight. We observe in them distinctly the great exertion 

 not only of the muscles of flight, but all the other organs of the body 

 also labour to support their flight ; and the cockchafer in particular, 

 which, doubtlessly, every one of our readers has observed in this occu- 

 pation, gives us a distinct idea of the great labour these little creatures 

 are obliged to apply to the execution of one of their most ordinary 

 occupations. We see it at first, as it were conscious of its increasing 

 labour, slowly raise itself, expand its antennae, and, in the endeavour 

 to free itself of a burdensome and hindering load, adapt itself to its 

 purposed course by violent respiratory motions of its abdomen. It has 

 hardly cast this burden from it, when it forthwith commences with 

 considerably increased activity its pedestrian journey, seeking for some 

 elevated spot whence it may commence its aerial expedition ; and if it 

 do not speedily find one, its anxiety to fly urges it to endeavour from 

 the plain surface, but this impatience is frequently punished by the 

 failure of its exertions. But, having reached an elevated spot, it raises 

 its elytra during the violent backward and forward bending of its head, 

 then suddenly expands them as well as the wings, and at the same 

 moment makes its first elevating blow, after having, at the same time, 

 compressed the whole abdominal cavity by means of the flexible dorsal 

 integument, and thus driven all the air out of it. Thus, during flight, 

 respiration takes place only in the thorax, and the abdomen resumes 

 that function only when the creature alights after its completed course. 

 But then its first motions are very violent and powerful. 



The position of the body during flight in the air in this and other 

 beetles is not the usual, viz. the horizontal, but inclined obliquely 

 towards the horizon, in which inclination the head takes the more 

 elevated, and the anal extremity the lower place. The cause of this 

 oblique position I think may be found in the preponderance of the 

 abdomen, particularly during puberty, owing to the turgidity of the 

 internal genitalia, over the smaller and lighter thorax and head ; at 



