HUNGERFORD: AQUATIC HEMIPTERA. 179 



The Egg. 



Size. Len^h, .598 mm.; diameter, .234 mm. 



Color. Very pale greenish. 



Shape. Elongate oval, but not regular. Viewed laterally the top 

 line is nearly straight, while the lower line is curved. The anterior pole is 

 flattened on the side bearing the micropyle, which is a slightly curved, 

 cylindrical peg. The surface appears reticulated with irregular hexa- 

 gons when seen under compound microscope. 



Most of our knowledge of these curious little back-swimmers comes 

 from Heinrich Wefelscheid's paper, "Uber die Biologie und Anatomie von 

 Plea minutissima Leach," 1912. 



This writer made an extended study of the above species. He says it 

 winters as an adult. That the female is larger than the male and that 

 mating begins in May and reaches its height in early June. He figures a 

 mating pair, and states that they may remain in copula as long as two 

 hours. Eggs were found in the laboratory in decaying stems of "Ra- 

 nunculus aquatiles." They wei'e placed in the stem with the long axis 

 parallel with that of stem, which agrees with our observation on Plea 

 striola. Egg stage lasted three or four weeks, and the five larval stages 

 took one and a half months. He says only one generation possible, 

 though Kulgatz says apparently two. As to the life of the adult he 

 remarks: "Die Imago kann mindestens noch ein zweites Mai uber win- 

 tern und sich foi-tpflanzen." He found them preying upon Daphnians, 

 and said they lived a week wathout food (most any predator will do this), 

 and adds "Sie satzen dann meistens in den Blattescheln oder on den 

 Stenglen und sangten offenbar die Pflanzen safte ein." 



In regard to its power to fly, he states ''Dennoch scheint es mir nach 

 dem verhaltnismassig kraftigen Bau der Flugel nicht sweifelhaft zu 

 sein, dass das Tier, ebenso wie seine nahe verwandte N. glauca, noch die 

 Fahigkeit des Fliegens besitzt." He notes also that in the British Mu- 

 seum there is an example from Batavia taken at electric light. 



They are capable of making sounds under water and he reports finding 

 "Reibleisten" on the sternum of the mesothorax "mit Hilfe deren das 

 gei'ausch wohl erzeugt ^^^rd," and finds a tympanal organ in the meso- 

 thorax, as in Corixa. The remainder of his paper is devoted to many 

 interesting structural studies which he has made. His paper is a 

 doctorate dissertation and shows how much there is to be done with our 

 own species. 



Genus NOTONECTA L. 



BIOLOGY. 



At the close of his "Revision of Xotonectidae, Part I," Kirkaldy stated : 



"I had hoped to give an account in this paper of the metamorphoses of 

 N. glauca L. Unfortunately my attempts of rearing this species from the 

 ova during two seasons have been only partially successful. I have, how- 

 ever, reared three larval instars from ova deposited in captivity, and 

 am aware of two more, so that Notoivecta has at least five larval instars. 



'•In the ultimate and perhaps also the penultimate larval stage, the 

 species can always be determined by the structure of the head; in the 

 first three, however, the shape of the head and eyes does not resemble the 



