throughout the northern United States and Canada. It does not 

 drop off its host to moult, and is found upon it chiefly during the 

 winter and spring months. The scarcity of moose in some seasons 

 is attributed to the attacks of ticks in the previous spring, the pests 

 being present in thousands and causing the death of the host from 

 exhaustion following loss of blood. 



The non-parasitic part of the life-history begins in the spring, when 

 the engorged fertiUsed female drops off the host to o^'iposit. Under 

 laboratory conditions in British Columbia, oviposition began in April, 

 3,000 to 5,000 eggs being deposited by each female during the months 

 of May and June, and the larvae began to emerge in July. It was 

 found that the pre-oviposition period ranged from 7 to 134 days, the 

 incubation period from 33 to 71 days, and the longevity of the larvae 

 from 50 to at least 346 days. The combined periods range normally 

 from 159 to 479 days. The larvae attach themselves to their host 

 during the autumn, winter and spring months. 



Dunn (L. H.). The Lake Mosquito, Mansonia titillans, Wlk., and Its 

 Host Plant, Pistia stratiotes, L., in the Canal Zone, Panama (Dip. : 

 Culicidae). — Entom. News, Philadelphia, xxix, nos. 7-8, July- 

 October 1918, pp. 260-269 & 288-295. 



Prominent changes in the flora and insect fauna of the Canal Zone, 

 Panama, have been caused by the formation of the great artificial 

 lake covering more than 170 square miles and having a maximum 

 depth of more than 87 feet. Part of this area was known as the 

 " black swamp," and in this region, several square miles in extent, 

 a few scattered masses of Pistia stratiotes (wild water lettuce), the host 

 plant of Taerdorhynchus [Ma/nsoniu) titilla,ns (lake mosquito), occurred 

 in various small bodies of water. The spread of the plant at this time 

 was very slow, and the mosquitos were present in relatively small 

 numbers. However, with the rising of the lake the plants were 

 carried to the periphery of the inundated lowlands, where the thick 

 forest growth and stagnant waters offered good protection. Conse- 

 quently they increased so rapidly that large floating islands were 

 soon formed, covering the surface of the water in masses several 

 miles in diameter. 



The association of the larvae of T. titillans with the Pistia plant 

 was first discovered in 1910. The eggs are attached in a mass to the 

 under-surface of a Pistia leaf lying flat, or nearly so, on the surface 

 of the water. When the larva emerges from the egg it descends into 

 the mass of rootlets and pierces the thin outer skin of one of them with 

 its pointed air siphon, which remains in the opening, the larva com- 

 pleting its development attached in this manner to the host-plant. 

 It feeds on the microscopic plankton, desquamations from the plant 

 roots, and other vegetable debris foiind in abundance among the root- 

 masses, the particles often becoming attached to the larva in such a 

 way that it resembles a piece of decayed vegetable fibre. 



Under laboratory conditions tfhe larvae develop very slowly and are 

 difficult to rear, seeming to tlirive better in water that is stagnant 

 and quite foul with vegetable debris than in clean fresh water. When 

 placed in a dish containing no plant life the larvae are able to five for 



(C530) a2 



