BIONOMICS OF THE CHINCH BUG. & 



The data obtained in connection with the experiments on the 

 number and length of instars of 16 individuals have been summarized 

 in Table 3. In another series of approximately equal number, under 

 observation for about the same period as were those of 1919 given 

 in Table 3, four molts only were observed and the nymphs were then 

 in their penultimate stage. The length of the period of the first 

 instar, according to Table 3, varies from a minimum of 6 to a maxi- 

 mum of 18 days, the second varies from 4 to 9 days, the third from 

 3 to 31 days, the fourth from 6 to 26 days, and the fifth from 10 to 26 

 •days. Taking the averages obtained in the series, the period of the 

 second instar is the shortest, the third somewhat longer than the 

 second, the fourth slightly longer than the first, and the fifth much 

 the longest of all. The greatest number of days required for any 

 one of the individuals in the series to reach maturity was 94, and the 

 smallest number 51. The general average for the total length of the 

 immature period in the series is 66.43 days. 



It is not unlikely that the length of the instars and the length of 

 the immature period were somewhat extended, because the nymphs 

 were kept under somewhat unnatural conditions. In this study of 

 number and length of instars in this species small shell vials (30 mm. 

 in length) were found the most convenient and satisfactory. These 

 were stoppered with absorbent cotton and the cotton was moistened 

 as often as necessary when observations were made. Small bits of 

 ■cornstalks were supplied as food for the nymphs. It was necessary 

 to be very cautious to prevent an oversupply of water from gathering 

 <on the sides of the vials. When droplets gather the nymphs, in 

 crawling along the sides, are overcome by the water and become 

 helpless, and if not assisted to a drier place and the vial dried out 

 will die in a short time. 



ECDYSIS. 



A short time before the nymph casts its skin it becomes much 

 swollen, especially in the abdominal region. The abdomen is then 

 much wider than the thorax, particularly in the region of the fourth 

 and fifth segments. Before this it is about the same width as the tho- 

 rax or a little wider. The period during which the nymph has this 

 swollen appearance will be called the molting period, and prepara- 

 tions are then being made by the nymph to cast off its outer cuticular 

 layer. This period corresponds precisely to that in lepidopterous 

 larvae known as the molting period, during which the larvse become 

 sluggish, feed little or none, and prepare to shed their outer coat. 



Specimens used for drawings of the various nymphal instars by 

 C. V. Riley apparently were all in the molting stage, as the figures 

 representing the instars show the nymphs much swollen. These 

 drawings, therefore, are incorrect, even if the insect should have 



