182 The Philippine Journal of Science 1919 
WATER BUGS 
At least five species of water bugs merit our attention here 
because of the more or less severe bite that they can inflict. 
In the order of their size and importance, these are : Belostoma 
indica St. F. et Serv., the giant water bug, sometimes called 
the electric-light bug; Laccotrephes rohustv^ StM and Ranatra 
parmata Mayr, the water scorpions ; Sphaerodema rusticum Fab., 
the diver; and Micronecta quadt,ristrigata Bredd., the small back- 
swimmer. The first of these kills small fishes and then sucks 
their blood. It can cause great pain, if handled so carelessly as 
to permit it to pierce the finger with its sharp beak. The next 
three are only harmful when carelessly handled, and they feed 
principally on insects. The fifth is attracted to light and will, 
like Nephotettix, bite a person that may be near the light. 
ROBBER FLIES 
Of the same character as the foregoing as to habits might 
be mentioned the robber flies, belonging to the families Mydaidse 
and Asilidse. Their species are numerous in the Philippine 
Islands, and individuals are abundant on every sunny roadside. 
They are the most extensively predaceous of any flies, and while 
the largest Philippine species rarely exceed 30 millimeters in 
length, they do not hesitate to capture and suck the fluids from 
other flies, bees, wasps, beetles, and even moths and butterflies. 
They are only known to bite man when captured and carelessly 
handled, but the bite is painful in the extreme and they might 
well develop a marked bloodsucking tendency. 
THRIPS 
The thrips, small fringe- winged insects (Thysanoptera) , often 
are almost microscopic, and the largest rarely exceed 7 or 8 milli- 
meters in length; they feed habitually upon the juices of plants, 
the leaves of which they cause to curl at the edges, thus forming 
a retreat for their young. One species of this order has a 
decided predilection for human blood, and a sharp bite on the 
hand during the middle of a hot, sunny afternoon can almost 
always be attributed to these minute insects, especially if one 
be resting near a tree in an open field. The bite of these 
insects causes no further inconvenience than the momentary 
pain, which vanishes almost with the culprit, no swelling or 
itching being produced. 
TICKS 
It would hardly be proper to close this paper without refer- 
ence to a class of arthropod animals which, while it cannot be 
