208 THE NORTHERN MICROSCOPIST. 
Above and placed against the concavity of the labium, in which it 
lies, is the labrum, or upper lip, a transparent chitinous sheath, 
tapering to an acute point. In this are found five delicate fila- 
ments of great tenuity and transparency, readily defined under, say, 
a quarter-inch objective into a pair of delicate blades with a keen 
edge and strong scythe-like back, ending in nine or ten well marked 
saw teeth and a needle point. These are the mandibles. Next 
we have another pair of thin blades, also with a strong back, but 
without teeth and with a somewhat rounded point—the maxille ; 
and lastly the suctorial organ—the ligula or tongue—a filament 
with a spear shaped head, traversed by a clearly marked tube 
throughout its entire length. ‘The extreme delicacy and beauty of 
these various parts defy description. ‘They must be seen and ex- 
amined under the microscope to be duly appreciated. Now itisa 
remarkable fact that the female Gnat or Mosquito alone possesses 
a full complement of oral organs. The male is destitute of man- 
dibles, maxillee, and ligula. He cannot therefore bite, and is 
quite a harmless inoffensive creature. If we are so unfortunate 
then as to be bitten, we may be sure that our guest isa female. In 
British Guiana, to which my remarks principally refer, and else- 
where in South America and the West Indies, there exists a variety 
of the Mosquito remarkable for its greater size and ferocity, and 
differing from both Culex mosquito and C. pipiens in having 
labium, abdomen, and legs clearly marked with bands alternately 
dark and light coloured, this appearance being due principally to 
the arrangement of the scales. Itis known as Culex pulicularis— 
locally as the Gallinipper. It is fortunately much less abundant 
than the common Mosquito which flourish in enormous numbers, 
varying with the season of the year and local conditions. ‘These 
are most numerous after the longer and shorter rainy seasons, 
March perhaps being the month most congenial to them, and again, 
along the coast and up the rivers as far as the tide extends. Stagnant 
waters and mud seem to be a necessity, as in the upper reaches of 
the streams, where there is a steady flow of clear, fresh water, they 
are comparatively rare. ‘There seems to bea periodicity also about 
their daily movements governed to a considerable extent by the 
prevailing local winds. ‘They swarm out in the evening, at sunset, 
for three or four hours, then follows an interval of rest until, say, 
five in the morning, when they again turn out, to retire again about 
eight for the remainder of the day. In the rainy season, however, 
when there is little or no breeze and a dull, close atmosphere, they 
are present throughout the entire day and night, but still in greater 
numbers at the times mentioned. Europeans, especially new 
arrivals, suffer severely from Mosquito bites, as do the negroes, and, 
I am assured, the aboriginal Indians themselves. It is curious to 
note the difference in the after effects observable in different indi- 
