HYMENOPTERA. 207 



nests she has prepared for them, which are frequently constructed 

 with so much art as to excite our wonder and surprise, and some- 

 times by depositinp^ her eggs in the body of the larvae and nymphs of 

 Insects, on which hor progeny are to feed. 



Other larvae of Hymcnoptera, also destitute of feet, require more 

 elaborated and frequently-renewed supplies of aliment, both vegeta- 

 ble and animal. These are reared in common by neuters forming 

 communities, of which they have the sole care ; their labours and 

 mode of life will always continue to excite our admiration and as- 

 tonishment. 



Almost all Hymenopterous Insects, in their perfect state, live on 

 flowers and are usually most abundant in southern climates. Their 

 period of life, from their birth to their ultimate metamorphosis, is 

 limited to a year. 



M. Leon Dufour in his Memoire sur VAnatomie des Scolies — 

 Journ. de Phys., Sept. 1828 — remarks, that in all the Hymenoptera 

 submitted to his scalpel, the tracheae are a degree more perfect than 

 those of the other orders of Insects ; that instead of being formed by 

 cylindrical and elastic vessels, tlie diameter of which decreases by 

 their successive divisions, they present constant dilitations, decided 

 vesicles favourable to the greater or less permanence of air, and sus- 

 ceptible of extension and diminution, according to the quantity of 

 that fluid admitted. On each side of the base of the abdomen may 

 be found one of these vesicles ; it is large, oval, and of a dead lacte- 

 ous- white, giving off here and there vascular tracheae which are dis- 

 tributed among the adjacent organs. In penetrating into the thorax 

 it is strangulated, dilates again, and insensibly degenerates into a 

 tube, the subdivisions of which are lost in the head. Behind these 

 two abdominal vesicles, the organ of respiration continues on in two 

 filiform tubes, giving off an infinity of ramous branches, and becom- 

 ing confluent near the anus. In the Xylocopae and Bombi, the an- 

 terior superior surface of each of the two great abdominal vesicles is 

 furnished with a cylindrical, clastic, greyish body, but adhering 

 throughout its length in the Xylocopae, and free in the Bombi. M. 

 Dufour thinks that this body, which is directed towards the insertion 

 of the wing, has some part in the production of the humming noise 

 made by these Insects, inasmuch as that sound may continue after the 

 wings have been taken off". 



I will divide this order into two sections. 



The first, or that of the Tkrebrantia, is characterized by the pre- 

 sence of an ovipositor in the females. 



I divide this section into two great families. 



