124 TEXT-BOOK OF ENTOMOLOGY 



More recently (189G and 1807) Osten-Sacken recommends "squamae in the 

 plural, as a designation for both of these organs taken together ; squama, in the 

 singular, would mean the posterior squama alone, and antisquama the anterior 

 squama alone ; ? ' the strip of membrane running in some cases between them, 

 or connecting the squama with the scutellum, should be called the post-alar 

 membrane. By a mistake Loew, and others following him, used the word 

 tegula for squama, but this term should be restricted to the sclerite of the meso- 

 thorax previously so designated (Fig. 90, A, t) . The squama or its two subdivisions 

 has also by various authors been termed alula, calypta, squamula, lobulus, 

 axillary lobe, aileron, cuilleron, schuppen, and scale. (Berlin Ent. Zeitschrilt, 

 xli, 1896, pp. 285-288, 328, 338.) 



The halteres. In the Diptera the hind wings are modified to form 

 the halteres or balancers, which are present in all the species, even in 

 Nycteribia, but are absent in Braula. 



Meinert finds structures in the Lepidoptera which he considers as the horno- 

 logues of the halteres of Diptera. "In the Noctuidae," he remarks, "I find 

 arising from the fourth thoracic segment (segment me"diaire), but covered by 

 hair, an organ like the halter of Diptera." (Ent. Tidskrift., i, 1880, p. 168.) 

 He gives no details. 



In the Stylopidse, on the contrary, the fore wings are reduced to 

 little narrow pads, while the hind wings are of great size. 



The thyridium is a whitish spot marking a break in the cubital 

 vein of the fore wing of Trichoptera ; these minute thyridia occur 

 in the fore wings of the saw-flies ; there is also an intercostal thyri- 

 dium on the costal part of the wings of Derrnaptera. 



The fore wings of Orthoptera are thicker than the hinder ones, 

 and serve to protect the hind-body when the wings are folded ; they 

 are sometimes called tegmina. It is noteworthy, that, according to 

 Scudder, in all the paleozoic cockroaches the fore wings (tegmina) 

 were as distinctly veined as the hinder pair, " and could not in any 

 sense be called coriaceous." (Pretertiary Insects of X. A., p. 39.) 

 Scudder also observes that in the paleozoic insects as a rule the fore 

 and hind wings were similar in shape and venation. " heterogeneity 

 making its appearance in mesozoic times." In the heteropterous 

 Hemiptera, also, the basal half of the fore wings is thick and cori- 

 aceous or parchment-like, and also protects the body when they are 

 folded; these wings are called liemelytra. In the Dermaptera the 

 small short fore wings are thickened and elytriform. 



The elytra. This thickening of the fore wings is carried out to 

 its fullest extent in the fore wings of beetles, where they form the 

 sheaths, shards, or elytra, under which the hind wings are folded. The 

 inflexed costal edge is called the epipleurum, being wide in 1lu Tciic- 

 brionidse. During flight "the elytra are opened so as to form an 



