December, '16] WATSON: velvet-bean caterpillar 525 



Sixth Instar. — The stigmatal line is colored like the lighter forms of the fifth 

 instar but the pink is usually replaced by brown. 



The caterpillar spends from five to twenty days in this instar, the 

 time becoming gradually' lengthened as the weather becomes cooler. 

 The length of the full-grown larva varies from 38 to 48 mm. In the 

 pre-pupal period it shrinks to a length of 25 mm. and turns mahogany 

 brown with few if any signs of longitudinal lines. 



Pupa. — Brown in color, smooth and shining. Abdominal segments punctuated 

 with fine dots which are particularly thick on the anterior half of each segment. 

 Head somewhat pointed. At the end of the abdomen are three pairs of hooked 

 spines, one pair is much larger than the others. Length 18-20 mm., width 4-6 mm. 

 The pupa is light green until it is about a day old. 



The pupae are usually placed barely underneath the surface of the 

 soil, but as there are usually many dried leaves under the vines they 

 are well hidden. They are placed in loose and frail earthen cells. 

 In the breeding cages and sometimes in the field these cells are made 

 of dried leaves or omitted altogether. The pupal stage averaged 

 about seven days in August and between ten and eleven in September. 

 As the weather became cooler this time was gradually lengthened 

 until those that pupated in November averaged 21 days and two that 

 pupated on November 20 and 21 respectively issued on January 7, 48 

 and 47 days respectively. 



The Moth. — Like the caterpillar, the moth also is very variable 

 (PI. 40). The ground color varies from a light yellowish brown 

 to ashen gray or a dark reddish brown. Old, badly rubbed individuals, 

 are brownish yellow with the color pattern almost obliterated. Usu- 

 ally, however, there is at least a trace of the diagonal line remaining. 



Beneath the wings are cinnamon brown with a sub-marginal row of 

 light spots and a median dark line. This color pattern is less variable 

 than that of the upper surface (PI. 39, fig. 4). 



Mating probably occurs at night. A single pair was observed mating 

 in the cages. This occurred about dusk. They remained in coitu 

 only a few seconds. Dusk is the period of greatest activity of the 

 moths. During the day they lie hidden under the leaves of the host 

 plants. If disturbed they fly a short distance only. They do not go 

 to lights readily and on the whole it would seem that they are not in 

 the habit of taking long flights. Doubtless, however, in the absence 

 of the host plants of the larva^, they are capable of long sustained 

 flight. There is no suggestion of definite broods. The moths seem to 

 arrive in numbers from the south during August and at any time after 

 late August one may find all stages in the field on the same day. 



