THE CLASS OF INSECTS. 



tion of the head into the rudiments of the ophthahnic ring, and 

 tlie supraclypeal piece, and clypeus, together with the approx- 

 imation of the second pair of maxilla;, wliich, when united, form 

 the labuim, tlie extremities of which are now situated in the 

 middle of the bod}'. 



The antennae now extend to the middle of the labium, just 

 passing beyond the extremities of the mandiljles and maxillae. 

 The oesophagus can now be seen going from the mouth-opening 

 situated just beneath the labium. It curves around just behind 

 the eyes. There are at this period no appearances of movable 

 blood-disks or of a dorsal vessel. 



The abdomen is now pointed at the extremit}^ and divided 

 into the rudiments of the tAvo anal stylets, which form large, 

 acute tubercles. The j'olk-mass is now almost 

 :ifsi-^-\.-E entirely inclosed within the bod}' walls, form- 

 ing an oval mass. 



Another embryo, observed July 27th, had 

 reached about the same stage of growth. The 

 front of the head, including the antennary 

 segment, is farther advanced than before. The 

 entire head is divided into two very distinct 

 regions ; i. e. one before the mouth-opening 

 (the preorcd region, including the ocellary, or 

 first and second segments; the ojyhthahnic, or 

 third segment, and antennary, or fourth seg- 

 ment of the head) ; and the other beJiind the 

 mouth (2)ostoral, consisting of the mandibular, 

 or fifth segment, the first maxillary, or sixth 

 segment, and the second maxillary, or labial, being the seventh 

 and last cephalic ring. 



At a later period the embryo is quite fully formed, and is 

 about ready to leave the egg. The three regions of the body 

 are now distinct. The articulations of the tergum are present, 

 the yolk-mass being completely inclosed by the tergal walls. 



Fig. 61. The embryo taken from the egg, but nearly ready to hatch, t, the 

 dotted line crosses the main trachea, going through the yolk-ma^s, now restricted 

 to the thoracic region. At x, the trachea; send ofl" numerous branches around an 

 enlargement of the intestine (colon), where the blood is aerated; better seen in fig. 

 62. The abdomen consists of eleven segments, the last being a minute triangular- 

 piece. 



