134 Mr. J. W. Dunning on 



aquatic plants below the surface ; it has gills, and lives 

 freely in the water. It has been figured by Brown. It 

 appears to feed exclusively on the pond-weeds, but has 

 been found on several species ; thus Kolenati (who, how- 

 ever, was acquainted with the imago only) mentions 

 Potamogeton heteropliyllus and perfoliatus j Brown and 

 Heineraann mention P. pectinatus and p) erf oliatus ; Ritsema 

 mentions P. crispus; and Milliere mentions P. pectinatus 

 and lucens. When fally fed, in June or July, the larvae 

 may be found " in silken cocoons, which are strengthened 

 by small pieces of the leaves incorporated longitudinally 

 in the fabric, and which are placed in the submerged axils ^^ 

 of the thread-like leaves of the Potamogeton. Brown 

 found only fully-fed larvae, but Ritsema and Reutti found 

 them in various stages of growth. 



The pupas are described by Brown as " of the masked 

 character, and the external case enables one to see 

 clearly which will produce males and which females ; " 

 both the male and female pupae are figured by him, and 

 exhibit three remarkably prominent spiracles on each side. 

 To acquire the pupae, Knaggs recommends dragging the 

 stream or pond with a water-net, where Potamogeton g'rows, 

 examining it on the shore for the small silken cocoons. 



The imago appears in June, July, and August ; though 

 not continuously for the whole period. During the three 

 months mentioned, the insect may be found in all its four 

 stages of egg, larva, pupa, and imago ; and it would seem 

 that about ten months of the year (including the winter 

 months, as with Hydrocampa and Paraponyx) are passed 

 in the larval state, and about one month in the pupa. 



The male imago is much more common, or more com- 

 monly observed, than the female ; occasionally it is found 

 in swarms. Kolenati captured forty-two specimens in 

 the Neva, all males; Nolcken went to the same locality, 

 and took something like 150, again all males. Zeller 

 had it in numbers from Pomei-ania, but only of the male 

 sex. Hagen had seen it in numbers, but could not 

 remember a single female taken in Prussia. Dale, in the 

 last letter I had from him (within three months of his 

 death, when the veteran entomologist was over eighty) , 

 wrote ''the males were in great abundance, the females very 

 rare.^' Brown, in a recent letter, writes " I have seen, I 

 should almost say, hundreds of males on the wing at a time. 

 Ritsema took fifty specimens near Haarlem, all males. 



Unless disturbed, they are inactive by day, but fly 

 briskly in the evening over the surface of water. Kole- 



