The Biology of Maine Species of Altica. 169 



Color cycle. When the pupa is first formed, it is a pure 

 creamy white, save for the caudal spines which are black, and 

 the setae and spiracles which are brown. As the pupa grows 

 older, however, certain color changes appear, which are correla- 

 ted with the progress of the internal metamorphosis, and furnish 

 a reliable indication as to the age of any given pupa. 



The first change to be noted is in the eyes, which become 

 a light brown on the third day of pupal life, dark brown on the 

 fourth, and black on the fifth. The wings become light gray 

 usually on the fifth day, although sometimes it is as as late as 

 the seventh day before this change appears, and a dark gray 

 about 24 hours later. The elytra remain colorless, although as 

 they lie over the wings, they appear to be colored. The mandi- 

 bles become red brown on the fifth day. 



The Adult. 



Emergence. \\ 'hen the adult is ready to emerge, the elytra 

 are pushed more or less dorsad, and the appendages are more 

 or less straightened out before the skin cracks. The pupal cuti- 

 cula cracks open along the dorsal line of the mesothorax; this is 

 done by the scutellum, which is raised and lowered. At this 

 same time the wings and elytra begin to increase in size, and 

 about five minutes after the first slit appears, these appendages 

 are about three-fourths as long as the body ; meanwhile the meta- 

 thorax has split way down the mid-dorsal line, and the mesotho- 

 rax way up. In 8 minutes, the prothorax is free, and the head is 

 exposed as far as the labrum. In 10 minutes the elytra and wings 

 are as long as the body, the mouth parts are all free from the 

 pupal cuticula, and the elytra about one-quarter exposed. All 

 through this process, .the insect continually contracts and expands 

 the abdomen. 



In 5 minutes more, the elytra are about half free, as well as 

 6 joints of the antennae, and one-third of the prothoracic femora. 

 The antennae are freed by jerking the head backward as far as 

 possible and then suddenly releasing it. In 24 minutes after the 

 first split the right prothoracic leg was freed, and two-thirds of 

 the elytra exposed. In 27 minutes, the left prothoracic leg was 

 also freed, and a minute later the mesothoracic and metathoracic 

 legs were drawn out almost simultaneously. In 33 minutes, the 



