RELATIONS AND DIVISIONS Oil THE CLASS INSECTA. 11 
upper pair modified, hard and horny in texture and 
forming sheaths (or elytra) for the lower ; mouth 
mandibulate ; metamorphoses complete, but the pupa 
has the outlines of the undeveloped image visible 
(v. p. 16). 
Hymenoptera. Wings four (frequently absent in 
ants and certain Ichneumonidse), membranous, without 
scales, and transparent ; mouth mandibulate ; meta- 
morphoses complete, but the pupa as in the preceding 
order : the chief divisions ai’e the Aculeate Hymenop- 
tera, in which the females and workers are provided 
with a sting connected with a poison gland, or at all 
events with a poison gland (“Ants, Bees, and Wasps ”), 
and the Non-aculeate Hymenoptera, in which no poison 
gland or sting is present (Saw-flies, &c.). 
Diptera. Anterior pair of wings only present, 
posterior pair replaced by knobbed processes called 
“ halteres •/’ which have usually, but perhaps wrongly, 
been considered as their homologues ; wings mem- 
branous, bare, and transparent; mouth with the parts 
modified, forming a sucker ; metamorphoses complete. 
The Diptera . genuina comprise all the species 
ordinarily known to us as “ Flies ” (House-flies, Meat- 
flies, Daddy Long Legs, Midges, &c.). 
The Pupipara are a small group in which the larvae 
and pupae are developed in the body of the mother ; 
they are all parasitic, and include the Bird-flies, Sheep- 
tick, and the Bat-parasites (Nycteribia). 
The Apha.niptera, including the Fleas and the Chigoe 
or Jigger, are by many authors considered a distinct 
order, as they differ from the true Diptera in the well- 
defined thoracic divisions and developed labial palpi, 
as well as in their laterally compressed form. 
