126 GNATS OR MOSQUITOES — CHAPTER VII 



ends. His measurement of the eg^ is given as onlyO"57mm. 

 As in other insects the egg doubtless varies in size. 



" The colour of the egg soon after it is laid is greyish 

 black. If the eggs are subject to much attrition a delicate 

 membrane splits off which gives the surface of the intact 

 egg its reticulated appearance. Stripped of this membrane, 

 which desquamates in irregular whitish fragments, the egg 

 appears with a glistening black surface comparable to that 

 of patent leather. One end of the egg is slightly blunter 

 and more rounded than the other, and this contains the 

 head end of the embryo. It is an interesting point that 

 when the egg, as frequently happens, is drawn by capillary 

 action a little way up from the water on to a leaf or some 

 other half- submerged object the head or blunt end always 

 points downwards, and thus should the hatching take place 

 whilst the egg is in this position the larva emerges into 

 the water, and not into the air." 



I doubt if these ova can resist more than a very 

 temporary dessication, but it is very difficult to judge of 

 this point by laboratory experiments, as not unfrequently, 

 they refuse to hatch out at all. The ova of some Stegomyice, 

 however, which resemble them a good deal, being laid 

 separately, and having also similar lateral floats, are cer- 

 tainly much more resistant, and may apparently be unin- 

 jured by being left high and dry for a month. 



Carroll, Agramonte, and Lazear {Philadelphia Med. 

 Journ., October 27, 1900, p. 291), state that in experiment- 

 ing on conveyance of yellow fever by Mosquitoes {Stegu- 

 myia, fasciata, Fabr.), they obtained a supply of this 

 species from Dr. Finlay. Thirty days previously, vide 

 Finlay, ova had been deposited by a female just at the 

 edge of the water in a small basin, whose contents had 

 been allowed to slightly evaporate, so that these ova, at the 

 time of their visit, were entirely above contact with the 

 water. Notwithstanding this long interval, they were 

 promptly converted into the larval stage, after a short period, 

 by simply raising the level of the water in the basin. 



The separately-laid eggs of PanopUtes have a very pecu- 

 liar shape, like a long, narrow pear, one end being prolonged 

 into a sort of neck exactly like that of a Florence flask. 



