68 INSECUTOR INSClTli^e MENSTRUUS 



abdomen would have been under the water. The freshly laid 

 cluster was white and the individual eggs of the single-spined 

 type. The surface of the cluster between the spines glowed 

 with air-bubbles. The eggs darkened very slowly. 



"I think it is quite possible that when ovipositing the abdo- 

 men of titillans, although thrust beneath a leaf resting upon 

 the surface of the water, does not get wet. It is, perhaps, at 

 work in a globule or a layer of air, for, owing to the dense 

 pilosity of the Pistia leaf, the under-surface is simply aglow 

 with air-bubbles, so that the leaf probably rests more on air 

 than on water." 



It is interesting to note in this connection that the abdomen 

 of the female Mansonia titillans is unusually hairy, the hairs 

 being well distributed and coarse. This is no doubt an adapta- 

 tion that by entangling air prevents the body itself from be- 

 coming wet while immersed. The remarkable structure of 

 the eggs, and their arrangement, no doubt serves the pur- 

 pose of keeping them supplied with the necessary air in their 

 submerged position. The difference in the eggs of the two 

 species will be difficult to explain satisfactorily. Professor 

 Moore suggests that the branched horns of the one type may 

 be a protection against enemies. We are inclined to think that 

 it is connected in some way with the problem of air-supply, 

 the eggs of the two species perhaps being deposited in slightly 

 different relation to the water. 



Finally should be noted the fact brought out by Professor 

 Moore's notes that in Mansonia titillans there is a very definite 

 relation between blood-meals and oviposition. In four cases 

 noted oviposition followed the blood-meal after an interval of 

 from four to five days. One female laid two batches of eggs ; 

 she was fed on January 15 and oviposited on the night of the 

 19th ; fed again on the 20th, she laid a second cluster on the 

 25th and died two days later. 



