Alliance 8. Spiessmucken. Four setæ within a hastate horny proboscis with or without arrested labia; third antennal joint not annulated, with the bristle or awn at the extremity—Tanystomidæ, as Asilidæ, Empidæ, Bombylidæ.
Alliance 9. Stielmucken. Four or six setæ within a thick-lipped proboscis; third antennal joint stipiform and annulated—Stratiomydæ and Tabanidæ.
Order 2. Leech-flies—Hymenoptera.
3520. Four naked veined wings, labium mostly elongated, the two pairs of maxillæ acting above it like spears. Larvæ mostly apodal, or with more abdominal feet or prolegs than in the true Caterpillars.
Most of the larvæ still bear a great resemblance to the Entozoa, though they do not respire like them through the anus, but by lateral apertures or spiracula; the larvæ with abdominal feet repeat the Nereidæ and Aselli. In other respects they live no longer in putrid moisture, fungi, roots, and such like bodies, but in living animals or in cavities specially prepared for their reception by the parents, and even in a state of freedom upon leaves.
And here is particularly worthy of our notice the structure of the cells, which are by many species fabricated quite substantially of wax or wood-shavings, and are to be compared with the webs of Spiders, since both serve as nests for the young. They repeat the Polypidoms.
Others make cases of leaves, and carry into them honey upon which to deposit their ova.
Others again simply bore holes in wood or in the earth, in order that they may in a similar manner provide their young with honey or larvæ. Finally, others simply stick, by means of their ovipositor, the ova into animals or leaves.
The dwellings are fabricated by the maxillæ, which but seldom serve as cibarial instruments, seeing that the labium undertakes this office as a lick-organ.
Another remarkable feature of this order is the arrested development of the sexual parts of the females in certain generations, an occurrence which depends upon the time of the year or the size of the cells, and whereby they are constrained to lead a social life as workers.