322 
[May 2, 
have no such clew to then- ancestry as is afforded in the Lepidop- 
tera by the lower Tiueina, such as Micropteryx, which is not far 
removed from the Trichoptera, and we have no such strong 
analogies to tlie larval Mecoi)tera (Panorpidae) which suggest that 
forms like them may have given rise to the Lepidoptera. The 
Diptera thus stand off b}' themselves as a side branch of the 
insect class ; though it should be borne in mind that the larvae 
and pupae, especially the latter, of lepidopterous, dipterous, and 
hymenopterous insects are more closely related than those of 
other orders. The mouth-parts of the larval Siphonaptera are 
not apparently formed on the dipterous type, so to speak, though 
the primitive or ancestral forms of larval dipterous mouth-parts 
are not now perhaps to be found. 
The antennae present no characteristic difference from coleop- 
terous and dipterous larvae. 
The mandibles are naturally of little taxonomic value in any 
group, since they are so obviously adapted to the nature of the 
food, but in the larval fleas they are perhaps of a more general- 
ized nature than in any of the Diptera. The Mycetophilidae 
appear on the whole, unless the Cecidomyiidae and Bibionidae, 
of whose mouth-parts we know nothing, be excepted, to have the 
most perfectly formed head. But the mandibles as described and 
figured by Osten Sacken^ are much more rudimentary than those 
of the young ilea, which in general shape nearest approach those 
of Tanypus (Fig. 7). 
The maxillae of the larval Diptera 
eucephala are said by Meinert to 
have in general but a single large 
lobe ; they are, however, two-lobed 
in Culex, Dixa (Fig. 8), and Simu- 
liuni (Fig. 9) ; the "outer lobe" 
of Meinert (lacinia) is the larger ; 
the inner, the galea, is the smaller 
and armed with bristles in Culex. 
The maxillary palpi except in Cera- 
topogon are always distinct, often 
Fig. 7. Tanypus varius ; mx, cyhndrical, prominent, and at- 
maxilla; Z6, labium ;p/), pharyn- ^ , n, i • t o- 
, ,' . \, , taclied to a palpanum. in Sinui- 
geal plate; sp, spinneret; mcl, ' ^ . 
mandible ; other lettering as in li^i"! the palpus is tvvo-jomted . 
prc'vions figures. --xlAej-il/euicr^. Osten Sacken describes the max- 
1 Proc. eiit. soc. Phil., 1, p. 151, pi. 2. 
mx.p 
