264 ENTOMOLOGICAL NEWS. | 'July, 'l8 



changed to a dark brown in a few hours. They were usually 

 scattered over the surface of the water. Under natural con- 

 ditions the eggs are attached to the under surface of a Pistia 

 leaf lying flat, or nearly so, on the surface of the water. 



While ovipositing the female clings to the edge of the leaf 

 or hangs suspended by her legs between two leaves that are 

 nearly contiguous. The lower end of her abdomen curves be- 

 neath the edge of the leaf and the eggs are attached in a mass 

 to its under surface. 



Ordinarily mosquito larvae live free in the water and secure 

 their air supply at the surface. This species adopts a some- 

 what different mode of procedure. The breathing tubes in 

 both the larval and pupal forms are so modified as to enable 

 them to attach themselves to the roots of the Pistia and se- 

 cure their air supply directly from the plant at some distance 

 from the surface. When a young larva of M. titillans 

 emerges from the egg it descends into the mass of rootlets of 

 the plant and pierces the thin outer skin of one of them with 

 its pointed air siphon. The siphon remains in this small 

 opening and the larva grows and passes the larval stage at- 

 tached to the host plant in this manner. 



The filamentous roots of the Pistia forms a mass heavy 

 enough to cause them to hang straight downward in the wa- 

 ter. The larvae, when attached, also usually hang with head 

 downward. Naturally the anal gills extend outward in an 

 opposite direction from the air-siphon. Occasionally the lar- 

 vae are observed to change this position and lie extended at a 

 right angle to the root. It has also been noted that while in 

 this horizontal position they frequently swing around with a 

 circular motion, the attached siphon acting as an axis. Very 

 likely this latter position is assumed while feeding. It is 

 very probable that they feed on the microscopic plankton, 

 desquamations from the plant roots, and other vegetable de- 

 bris found in such profuse abundance among these masses of 

 roots. Larvae have been observed so thickly coated with 

 small particles of decayed vegetable matter that, when in the 

 water, they could hardly be recognized as larvae, if attention 



