606 SCIENTIFIC RECORD FOR 1884. 



four species of the genus, all of which inhabit India and the neighbor- 

 ing islands. It seemed to Mr. (Cambridge th:it the whole phenomenon 

 described is "easily explained by the oi)ei;ition of natural selection, 

 without supposing consciousness in the spider in any part of the pro- 

 cess. The web on the surface of the leaf is evidently, so far as the 

 spider has any design or consciousness in the matter, s{)un simply to 

 secure itself in the proper position to await and seize its prey. The 

 silk, which by its lineness, whiteness, and close adhesion to the leaf 

 causes it to resemble the more Ihiid parts of the excreta, would grad- 

 ually' attain those qualities by natural selection, just as the spider 

 itself would gradually, and proba^sly pari pasiiii, become under the in- 

 tiuence of the same law, more and more like the solid portion."' {Proc. 

 Zool. Soc. London, 1883, pp. 58G-5S8, i)l. 51 ; 1884, p. lOG-203, id. 15.) 



Insects. 



The mouth parts of suctorial Insects. — In connection with a memoir on 

 the systematic position of the PuJicidn', Dr, Karl Kriipeliu has disc::.ssed 

 the structure of the mouth parts not oidy of the Fleas, but of the foi nis 

 with which they have been associated by other authors, the Di[)tera 

 and Hemii^tera, and the results are of considerable systematic impor- 

 tance. It is found that the suctorial insects segregate theniselves into 

 two primary grou])s. In one, consisting of the Uymeno])tera and Lep- 

 idoptera, the suctorial organs are characterized by the lower parts of 

 the mouth, maxillse and labium, being employed in the formation of a 

 sucking ai)paratus, while in another group, represented by the Diptera, 

 Siphonaptera, and Ilhynchota, it is almost exclusively the ui)per parts, 

 labium and mandibles, that are implicated in the fornration of the true 

 food canal. The characteristics of the mouth parts of the three orders 

 of the latter section are thus diagnosed by Dr. Krapelin : 



(1) Diptera. — " Insects with perfect metamorphosis. Head free, with 

 facetted eyes. Sucking-tube formed by a dorsal and a ventral half- 

 channel (labrum and hypopharynx), more or less inclosed throughout 

 its length by the labium, which is bent uj* like a sheath, and furnished 

 with uniarticulate apical palpi. Mandibles deficient or styletiform, 

 pushing in between the labrum and hypopharynx. Maxilla^., when pres- 

 ent, with i)ali)i. Salivary efferent duct an unpaired closed canal in the 

 interior of the hypo])harynx. A ' sucking-stomach.' Thoracic segments 

 amalgamated, usually with a pair of wings and a pair of halteres." 



(2) Siphonaptera. — " Insects with perfect metamorphosis. Head at- 

 tached to the thorax by a wide surface, without facetted eyes. Buccal 

 organs suctorial. Sucking-tube formed by a dorsal and two lateral 

 channels (labrum and mandibles), its anterior section only more or less 

 inclosed laterally by the mulitiarticulate terminal palpi of the labium, 

 and at the base, besides the latter, by the lamelliform palpigeruus max- 

 illae. Salivary efferent ducts paired, develojied as a channel along the 

 inner surface of the mandibles. Ko ' suekiug-stomach.' Thoracic seg- 



