genus Acentrapus. 279 



alarmed by something or otlier, or that the female had 

 dived down for the purpose of getting rid of the male. 



liitsema, however, never saAv an actual case of copula- 

 tion, though he was once very near it. But I will give 

 his OAvn Avords (p. 89, and compare Ent. Mo. Mag. xii. 

 257): — "At last fortune favoured me, at least so far that, 

 in the evening of the 1st of June, two males and two 

 females hatched, the latter with rudimentary Avings; but 

 it was so stormy that evening that 1 feared I should be 

 unable to observe the copulation if it took place. When 

 in the course of the evening I visited the aquarium, Avhich 

 stood in the garden, it Avas impossible to hold the lantern 

 for more than a moment, Avhich, hoAvever, Avas just suffi- 

 cient to see that the males were very nimbly hovering 

 round the females, chasing them on the surface of the 

 Avater. As the storm continued its violence, I visited the 

 aquarium no more that night. But I had seen enough to 

 make me suppose that copulation takes place, not in, but 

 on, the Avater, and that the female dives doAvn to lay her 

 eggs upon the food-plant." 



liitsema assumes that Reutti's account is the result of 

 a single observation, and omits to notice that lieutti's 

 statement is confirmed by Wallengren. It may be that 

 the latter author merely reproduces the former's statement 

 Avithout acknoAvledgment and Avithout having verified the 

 fact. But if so, hoAv stands the matter? 



liitsema's momentary glance by lantern light on a 

 stormy night Avas the one solitary opportunity he had of 

 making any observation on this subject, and all he can 

 say is, not that he saw them in copula, on the water, but 

 merely that he saw enough to make him suppose that the 

 act takes place on the surface of the water. Even if his 

 momentary peep revealed them in copula on the surface, 

 there is nothing to shoAV that the next moment the female 

 did not, as lieutti says, draAV doAvn the male Avith her. 

 And, granted that the act Avas completed on the surface, 

 Ave have only one observation by Ritsema against one by 

 Reutti. The most that can at present be said is, that 

 Reutti's observation has not been confirmed by Ritsema. 



The larva3 and pupaj live in the AA^ater, so that all the 

 moths are bom in the Avater. And Ritsema tells us that 

 the first female found in his aquarium Avas quietly craAvl- 

 ing over the Potamof/eton, vuider Avater ; that another 

 female, born in a bottle of Avater and thence turned into 

 the aquarium, swam about freely and came to rest on the 



