DIPTERA (TWO- WINGED FLIES). 
73 
completed, the specimen should be transferred to a store-box, or to one 
lined with cork-carpet or pith, as described above. Since, however, 
the tissues contract in dying, the legs and wings are very apt to get 
pulled out of place, and, to correct these changes, the specimens 
should be examined once or twice during the next day or two after 
being pinned. 
Very minute or fragile specimens are best pinned from the side, 
and the legs should then be straightened out by means of a No. 20 
pin held in the entomological forceps. 
dlptera collected in the tropics : 
Attacks by Ants — Mould— Transmission to England. 
In the tropics boxes of pinned insects are very liable to the attacks 
of minute ants, which, if they once gain access to a box unobserved, 
will soon play havoc with its contents. In Brazil it has been found 
that ants can be prevented from entering insect-boxes by smearing 
the outside round the line where the box opens, or any other possible 
place of entrance, with andiroba oil, repeating the process as often 
as necessary ; similar methods might be employed elsewhere in case 
of need. 
Mould, however, is an even greater enemy to collections of Diptera. 
Pinned specimens of Diptera, like those of other insects, rapidly 
develop mould during the rainy season in tropical countries ; and 
since mouldy specimens are practically worthless for purposes of 
scientific determination, Diptera should always be sent home as soon 
as possible after being collected. The risk of mould may, however, be 
diminished by pinning in a corner of the box a small piece of sponge 
saturated with the strongest carbolic acid, which should be con- 
stantly renewed. The greatest care must be taken to prevent 
specimens getting loose and rolling about in transit, since in this 
way a single loose disc might easily do irreparable injury to many 
other specimens in the box. To prevent this the pins supporting 
the discs should be inserted as tightly as possible into the cork- 
carpet or pith, and they should all be driven in to the same level, 
after which a sheet of soft paper (newspaper does very well) can be 
fixed into the box, resting on the heads of the supporting pins, in 
