ox INDIAN PARASITIC FLIES. 
967 
nycteribia with a single species from New Guinea may represent 
an ancestral type ; the first tarsal segment of the legs instead of being 
long and attenuated is exceedingly short and hardly so long as the 
three next segments put together ; there is no ctenidium or comb 
on the underside of the abdomen. 
No mere description can give more than a general view of the 
comformation of these remarkable Diptera.* There are no vestiges 
whatever of the front pair of wings but all species have halteres rep- 
resenting the second pair of wings. The retention of these stalked 
knobs in a group which does not fly is some confirmation of the belief 
that the halteres are not balancers but sense-organs. The separation 
of head, thorax and abdomen is clearly marked. The head is small 
and attached to the upper side of the thorax by such a slender and 
flexible neck that in dead specimens the head is often completely 
bent back. In such cases the back of the head rests on the thorax and 
the mouth parts are directed upwards to the heavens. It was at one 
time thought that Nycteribiids must turn over to feed but it seems 
uncertain whether this unusual posture of the head is ever adopted 
when the insect is alive. 
The conformation of the thorax and position of the legs is also 
singular. The lower surface is strongly protected with a dark and 
homy chitin whilst the upper surface is soft and of a yellowish white. 
It is just the reverse of what one finds in other Diptera. The ventral 
plate of the thorax projects in front vmder the head and to the rear 
beyond where the abdomen is rooted to the thorax. But the oddity 
does not rest there, for the three pairs of legs are inserted on the upper 
instead of the nether surface of the thorax. In fact the ventral plate 
is prolonged roimd the sides of the thorax. In death the six legs are 
contracted together over the back instead of under the belly as in a 
dead house-fly. In life the insects seem to be nmning about upside 
down or with belly uppermost. Although their native heath is the 
furry skin of a bat, they can make good progress on a mahogany table. 
The six legs of a Nycteribiid conform in general, as to structure,, 
with those of other Diptera and all the normal segments are present : 
coxa, trochanter, femur, tibia, tarsus. The following peculiarities 
are note-worthy. First in every species of Nycteribiid the femur 
is marked with a ring or furrow of lighter coloured and softer chitin 
which would seem to increase the flexibility and reduce the rigidity 
of the segment ; secondly, in two genera both of which are Indian 
{Cyclopodia and Encampsipoda) the tibiae are similarly marked res- 
pectively with two or three rings, as the case may be, which make 
the tibial segments more lissom ; thirdly, the tarsi have peculiarities 
♦ There is an excellent figure of a Nycteribiid in the Cambridge Natural History 
“ Insects ” and also in Mr. Hugh Scott’s jmper on these insects Parasitologj/ 
(1917) Vol. IX. p. 593. The coloured figure in Indian Insect Ltfe by H. Maxwell 
Lefroy, Plate LXIX, is too small to show the structure in detail. 
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