Lygaeidae 303 



REARING METHODS FOR CHINCH BUGS, BLISSUS HIRTUS 



Kenneth E. Maxwell, Cornell University 



FOR a study of the length of nymphal instars, it was desirable to 

 isolate individual nymphs and observe their moltings. A satisfactory 

 cage for this work was a %" x 2%" round-bottom flint shell vial, of the 

 same shape as biological laboratory test tubes. The tubes were stoppered 

 with cotton plugs and supplied with the stems of grass plants for food. 

 The food used was creeping bent grass, a variety in which the bugs breed 

 very readily and which is commonly used for lawns and putting greens 

 in the Northern United States. 



It was found necessary to replenish the food supply nearly every 

 day because of the drying out of the grass. The grass furnished both 

 food supply and moisture. Grass stems were cut at the base and im- 

 mediately immersed in water, where they were kept until ready for 

 use. Frequent moistening of the cotton plugs aided in maintaining a 

 high humidity. Attempts to conserve the moisture content of the grass 

 by the use of cork stoppers were not successful, due to the fact that 

 evaporation from the food material saturated the air, and moisture con- 

 densed on the glass. The insects, particularly the younger stages, fre- 

 quently stuck to the wet surface, and suffered a high mortality. 



The nymphs undergo five molts, with considerable variation in the 

 time required for each instar under different conditions. The shortest 

 time required from egg to adult, under field laboratory conditions, was 

 44 days, in contrast to the longest, which was 81 days. As many as 

 9 chinch bugs have been successfully reared through all stages in a 

 single tube, and a larger number may be used, depending on the food 

 supply. 



Oviposition. For fecundity studies of individual females, single pairs 

 were confined in the same type of cage as that used for life history 

 studies. Copulation occurred frequently during the oviposition period, 

 and some females oviposited daily for several consecutive days. There 

 is considerable variation in the fecundity of individual females, and ovi- 

 position fluctuated with the temperature and with the quantity of food 

 material and moisture present. Oviposition decreased with low tempera- 

 tures, and almost ceased when the prevailing temperature remained below 

 70 F. It was desirable to maintain a high humidity, keeping the air 

 as nearly saturated as possible without obtaining condensation on the 

 sides of the cages. No difficulty was experienced with fungus killing the 

 insects in the laboratory studies. 



When a female was ready to oviposit, she inserted her ovipositor be- 

 neath the leaf sheath, and deposited the eggs, sometimes singly, but 

 usually in groups. When the leaf sheath was pulled back, the eggs 



