312 Phylum Arthropoda 



Family notonectidae 



REARING NOTONECTIDAE* 



Buenoa mar gar it aec a, B. scimitra, B. elegans, Plea striola, and No- 

 tonecta undulata, all common species in Kansas, have been reared from 

 egg to adult. Successive generations have been raised in the case of several 

 of these species. 



Since about 1895 various attempts have been made to rear the noto- 

 nectids, but usually they have been only partially successful. The diffi- 

 culties have been in establishing conditions in the aquarium duplicating 

 those of the ponds or natural habitat of these insects. At least three 

 important factors have been at fault: the oxygen content of the water, 

 the condition of the surface film, and the food supply. 



In attempting to rear the early stages of Buenoa it was found that few 

 nymphs ever reached the 2nd instar in the stender dishes used. It even 

 took the eggs longer to hatch there than out in the ponds. Frequently 

 changing the water in the stender dishes did little good. When it was not 

 so changed, a scum formed over the surface after one or two days. The 

 bugs died more quickly. The daily removal of this scum helped the 

 situation but did not remedy it. It occurred that the trouble probably 

 was due to oxygen deficiency and the greater difficulty in breaking the 

 surface film when it was covered with scum. Air forced through the water 

 with a large pipette almost immediately revived the dying bugs, but the 

 relief was only temporary. Then a device first described in 19 10 ** for 

 continuously aerating an aquarium was used. It was a success, and 

 must be credited for the life histories of the genus Buenoa. 



Another difficulty was the food supply. Ostracods and such minute 

 organisms as the Buenoae and Pleae usually fed upon were inconvenient 

 to collect. Other workers had reported mosquito wrigglers as good food 

 for notonectids. So during most of the season mosquito eggs were col- 

 lected each morning from one or two tubs of rainwater and kept in a 

 smaller vessel until next day when they hatched and served well as 

 food for all species. A barrel of rainwater near the insectary supplied 

 larger mosquito larvae for the more mature nymphs and adults of 

 Notonecta and Buenoa. But even tiny Plea will not hesitate at times to 

 attack almost full grown mosquito wrigglers. 



Other factors than those just mentioned should be considered. The 

 laboratory in which the rearing work was done was in a basement which 

 affected the temperatures and lighting, and it was artificially heated 

 during the latter part of the season. All aquarium jars except a few kept 



♦Abstracted from an article in Ann. Ent. Soc. Amer. 19:93, 1926, by Clarence O. 

 Bare, Sanford, Florida. 



** Schaeffer, A. A. 1910. Science 31:955. 



