[ 55 ] 
XyhcQpa aestuans. Its male is entirely yellow, but the female 
is black with exception of the thorax which is yellow. A very 
handsome bee is Xylocopa caerulea. It is of sky-blue colour, 
but considerably rarer than the others. As the name 
Xylocopa indicates, these Humming Bees burrow in wood, 
drilling long galleries, which open to the exterior by cylindrical 
holes. Branches of trees showing such galleries are exhibited 
FLIES & FLEAS (Diptera). 
The Diptera include Flies, Gnats (or Mosquitoes) and 
Fleas. Their metamorphosis is complete. Their raouthparts 
are adapted for piercing and sucking. As the name ' Diptera ' 
indicates, these insects have only one pair of wings, or they 
may be entirely wingless, like the Fleas. The wings, when 
present, correspond to the forewings of other Insects. The 
hindwings have become reduced to a pair of minute clubs, 
called balancers or halteres. Their function is supposed to be 
to balance the insect when flying* No Diptera are exhibited. 
BUTTERFLIES A MOTHS (Lepidoptera). 
Butterflies and Moths undergo a complete metamor- 
phosis. They possess two pairs of wings which are clothed by 
minute scales. Their mouthparts are adapted for sucking. No 
definite line of demarcation can be drawn between Butterflies 
and Moths, but the following distinctions apply in the 
majority of cases : 
Butterflies (or Rhopahcera) have clubbed antennae; their 
fore and hind-wings are not interlocked at the inner margins, 
and the wings are placed vertically when at rest; they are 
chiefly diurnal; the chrysalis is not enclosed in a distinct 
cocoon. 
Moths (or Heterocera}^ on the other hand, have variously 
shaped, but not clubbed antennae ; their wings are interlocked 
and placed horizontally when at rest ; they are chiefly noctur- 
nal ; cocoons are present in many cases. 
No other group of insects or animals altogether have 
been so much collected and studied in the Straits as the Butter- 
flies. Distant, in his * Rhopalocera Malayana ' describes and 
figures above 500 species from the Peninsula alone. The 
Museum collection, arranged in 24 cases, contains most of 
them and many additional kinds from the Malay Archipelago. 
