Notes, iv. 6. 229 



them. Crustacea, then, are outside the group. It includes, however, not only insects 

 proper, which are A.'s Hexapodous insects, but also Myriapoda, which are his Poly- 

 podous and Wingless insects (iv. 5, Note 70). The third of the above-named characters 

 should exclude the spiders, scorpions, etc. But nevertheless these also are included in 

 the group by A., as indeed they were by modem naturalists until Lamarck separated 

 them in 1800. The fourth character, again, should exclude the parasitic worms. Yet A. 

 includes in the group both the flat and the round parasites (i¥. A. v. 19, 3), which he 

 calls by the general name of Helminthes. In fact, the only character on which he practi- 

 cally insists is the presence of segmentation ; and he even in one place {H. A. i. i, 16) 

 thus expresses himself: "I call all those animals insects, that show segmentation either 

 on the dorsal or the ventral surface, or on both." This passage must of course be read 

 with the limitations introduced in other places. Still it shows that segmentation was the 

 main character of the group in A.'s estimation. Probably therefore he included Annelida 

 in the group, led to this not only by their manifest segmentation, but by their retention 

 of life when cut into pieces, a character often mentioned by him as specially belonging 

 to insects. Some water annelids were certainly so included by him, being confounded 

 with Myriapoda. Cf. iv. 5, Note 70, 



2. Cf. iv. 5, Note 70. 



3. Cf. iv. 5, Note 71, and iii. 5, Note 2. 



4. The Diptera are as a rule of small size. Still the direct relation here stated to obtain 

 between the bulk of an insect and the number of the wings can hardly be said to exist. 

 There is however some relation between the size of the wings and the weight of the body. 

 "There are three classes of flies in this order {Diptera), the form of whose bodies, as 

 well as the shape and circumstances of their wings, is different. First are the slender 

 flies— the gnats, gnatlike flies, and craneflies. The bodies of these are light, their wings 

 narrow, and their legs long, and they have no winglets. Next are those whose bodies, 

 though slender, are more weighty — the Asilidae, etc ; these have larger wings, shorter 

 legs, and very minute and sometimes even obsolete winglets. Lastly come the flies, 

 Muscidse, etc., whose bodies, being short, thick, and often very heavy, are furnished not 

 only with proportionate wings, and shorter legs, but also with conspicuous winglets " 

 {Kirby andSpence, 7th ed. p. 476). So also there is a connection between the weight 

 of the body and the presence of wings. For while in most insects the tracheae dilate 

 into air-vesicles *' which are subservient to the diminution of the weight of the insect, in 

 the Apterous insects, and especially in the Myriapoda, there is no trace of these " {Owen's 

 Lectures, i. 225). 



5. The Melolontha of A. is certainly not the beetle now known by that name, viz. the 

 cockchaffer. For A. describes it {H. A. v. 19, 18) as coming from a worm that lives 

 in the dung of cattle and of asses. Very probably some such beetles as the Geotrupidse 

 are meant. These are stationary during the day ; and though they fly in the evening 

 " rasent la terre d'un vol court, lourd et sinueux." 



6. Frantzius translates thus : " Their wings also are not divided. For it is not a wing 

 at all, etc." But the word which A. uses for the wing of an insect {TrTfp6v) is the word 

 used for the feather of a bird, not for its wing (irTepiryl); and the comparison is not 

 between the wings of an insect and the wings of a bird, which A. knew to be perfectly 

 distinct parts though analogous in function, but between the wings of an insect and the 

 feathers of a bird, which do so far anatomically correspond to each other, as that both 

 are derivations from the common integument. (Cf. iv. 12, 3.) When, then, A. calls 

 insects dipterous and tetrapterous he has an eye to homologies ; when we call them two- 

 winged or four-winged we are thinking of analogies. 



