- Fic. 3.—Full-grown 
6 BULLETIN 889, U. S. DEPARTMENT OF AGRICULTURE. 
Comstock (8, p. 200) as early as 1879 gave a complete description 
of a full-grown larva, which is as follows: 
Length 8™™; color light yellow; tips of mandibles and anal horn brown. Sub- 
cylindrical in shape, the anal segment only being narrower than the preceding joint. 
Average width .9™@. Thoracic legs long and stout; only one prop 
leg, which is under the anal segment. The anal segment is armed 
upon its dorso-posterior border with two upward-curved acute 
hooks placed close together. The head is broad, somewhat flat- 
~tened dorso-ventrally. Antennz prominent, 4-jointed, 3d joint 
longest, 4th joint slender. Labrum broad, rounded, with a row 
of small piliferous tubercles at its anterior border. Mandibles, 3 
toothed. Maxillary palpi, 3 jointed. Labrum rounded anteriorly; 
labial palpi 2 jointed, stout. 
THE PUPA. 
The pupa (fig. 4) is yellow, slender, and semicylin- 
drical. The abdomen is darker in color than the rest 
of the body. The head is broader than either the 
thorax or abdomen, and the wing pads are prominent. 
The abdominal segments have short spines dorsally, 
by the aid of which the insect moves up 
and down the stem. 
ameaton Eherclowor LIFE HISTORY AND HABITS. 
stem-borer. THE LIFE CYCLE. 
The average time required for this beetle to pass its 
complete life cycle is about 60 days. This period is 
noticeably shorter during the first generation than dur- 
ing later generations. This is due to the fact that during 
this generation the time elapsing from the issuance of 
the adult to copulation and oviposition is considerably 
shorter than in the subsequent generations. The ap- 
parent cause for this is that later in the year the beetles 
tend to cease their activities for the season rather than 
to continue a third and sometimes a partial fourth gen- 
eration. The life cycle is shorter during the first genera- z 
tion in spite of the fact that the egg stage is considerably rig. 4—Pupa of 
longer than during the months of July and August. (See the clover 
rearing cage, fig. 5.) oe 
The minimum life cycle has been noted to be as low as 50 days, 
while the maximum has often extended through a period of 65 to 70 
days. The total length of the egg, larval, and pupal periods was 
found to average 49.1 days, with a minimum of 45 days and a maxi- 
mum of 58 days. Table I shows the combined length of egg, larval, 
and pupal periods of 20 specimens carried through, by the junior 
author, from egg to adult, but does not show the period existing 
between issuance of adult om oviposition, 
ta 
