METAZOA INSECTA. 441 



and Stylopidae, are instructive inasmuch as they throw 

 light on the life history of the group, while they also illus- 

 trate the changes that parasitic habits may produce on 

 insect structure. 



The Meloidae are represented by Epicauta vittata Fabr. 

 (PI. 1115; No. 1116). It lays its eggs (PI. 1115, fig. i) 

 in the ground, generally near the egg-pods of locusts. In 

 about ten days the larva, known as the triungulin (fig. 2), 

 hatches. It is soon light brown in color and very active. 

 Its flattened body with its well developed legs and its 

 cerci give it a Thysanuriform aspect. This larva bur- 

 rows through the mucous neck of a locust's egg-pod, 

 Melanoplus differentiates (fig. 3, egg- pod of M. differ en ti- 

 atis), and sucks out the contents of an egg. In time the 

 skin splits along the back and the second larva (fig. 4) 

 appears with the legs much reduced in size. Fig. 5 is a 

 side view of this same larva, showing its natural position 

 within the egg-pod. The last stage of the second larva 

 is shown in fig. 6. It now leaves the egg-pod and forms 

 a cavity in the earth in which it lies motionless, and is 

 known as the coarctate larva, called by fcabre pseudopupa 

 (fig. 7, with the skin adhering behind ; fig. 8, dorsal view 

 of same). The legs in this stage are little more than 

 tubercles. The insect usually hibernates in this condi- 

 tion. In spring the third larva appears, which is very 

 similar to the coarctate larva excepting that it is active; 

 but, although active, it seems to take little or no nourish- 

 ment. In a few days this larva transforms to a pupa (fig. 

 9, pupa of Epicauta cinerea Forst.) and in five or six days 

 the imago (No. 1116; PI. 1115, fig. 10) is fully devel- 

 oped. 



Thus it is seen that the Thysanuriform larva with well 

 developed legs becomes, by the laws of variation and 

 adaptation governing animals, a creature with a grub-like 

 form and small tuberculous legs. Specialization by re- 

 duction, however, is not carried so far as* to produce a 

 footless larva. 



