890 



INSECTA. 



the maxilla and galea seems more peculiarly 

 adapted to the phytophagous feeders, since in 

 the true carnivorous insects, Cicindtlid<?, tiger- 

 beetles, and the larger Carabida, ground-bee- 

 tles, the maxilla is more elongated, the inter- 

 nal lobe, or apex of the lacinia, is more acute, 

 and often armed with a sharp hook, and the 

 galea assumes the form of a distinct palpus, 

 shorter but similar in appearance to the true 

 maxillary palpus. This is more manifestly 

 the case in the tiger-beetles, in which the galea 

 is a distinctly double-jointed palpus, placed 

 on a feeler-bearer, and the lacinia is armed 

 with a long sharp hook, evidently more adapted 

 for seizing and piercing its living food, like the 

 canine teeth of carnivorous quadrupeds, than 

 for comminuting it like the strong tuberculated 

 galea of the vegetable-feeding Melolontha, or 

 the tuberculated teeth of herbivorous quadru- 

 peds. The office then of the galea, in dis- 

 tinctly carnivorous insects, is simply that of a 

 palpus or feeler, and in accordance with this 

 view we find that in the tiger-beetles it is 

 longer than the inferior lobe, or hooked por- 

 tion of the lacinia. In the ground-beetles 

 Mr. Newman has remarked that it is shorter 

 than the lacinia, but, in the generality of the 

 tribe, we have also found it longer, as in the 

 rapacious Cicindelidae, particularly in the lar- 

 ger Carabidtf, and this is also the case in some 

 of the Harpalida, particularly in one species, 

 Zabrm gibbus, which is known to be a vege- 

 table feeder. This form of the galea, however, 

 seems more peculiarly to belong to the carni- 

 vorous insects, as it is also found in the Dyti- 

 cidae, but not, as we have seen, in the nearly 

 allied but far less rapacious Hydrophylid<p.. 

 On the other hand, in most insects which feed 

 entirely on vegetable matter, the galea is of a 

 more obtuse form, and is less distinct from the 

 other parts of the maxilla than in the rapacious 

 insects. Thus in the greater number of the 

 true vegetable feeders the galea is short, thick, 

 and densely covered with hair. This is the 

 case not only with the maxillae, but also with 

 the mandibles in those insects whose food is 

 the pollen and perhaps also the honey of 

 flowers, as in the Cetoniida, and also in the 

 Geotrvpida and other Scarabteidx, which feed 

 upon soft decaying vegetable matter. In the 

 Cerambycida, as in the rare insect Monochamus 

 sarhrrf in the Lepturida, which are found 

 upon umbelliferous plants feeding on the pollen 

 and honey ; and in the stag-beetle, Lucanus 

 cervus, which subsists on the sap that flows 

 from the wounded bark or roots of trees, the 

 galea is always densely covered with hair, and 

 sometimes elongated to a considerable extent, 

 as in the stag-beetle. In those species which 

 are purely phytophagous, as many of the 

 Galerucidtf and Chrysomelidee, which feed on 

 the parenchymatous structure of leaves, both 

 the galea and lobus inferior are short, obtuse, 

 and covered with stiff hairs,while in the Core incl- 

 lid<E that very much resemble the latter insects, 

 but are carnivorous feeders, the galea is longer 

 and distinctly jointed, and resembles the same 

 part in Hydrous, being still covered with hair. 



* Curtis's British Entomology, pi. 219. 



This is also the case in the common meal- 

 beetle, Tenebrio rnolitor, which belongs to a 

 family of less distinctly vegetable feeders. 

 From these facts we are inclined to believe 

 that the structure of the maxilla has much 

 closer connexion with the kind of food and 

 habits of the insect than that of either the 

 labium or the palpi. The latter organs, how- 

 ever, are subject to great variation in the form 

 of the terminal joint, which in some species is 

 much dilated and shaped like a hatchet, as in 

 the common lady-bird, Coccinella, while in 

 others it is acute or obtuse. The number of 

 joints is usually four, and it has been sup- 

 posed that there are never more, either in the 

 maxillary or the labial palpi, in any Coleop- 

 terous insect, but the Rev. Mr. Kirby* has 

 mentioned an instance in which there appeared 

 to be an anomalous condition of the maxillary 

 palpi, in this respect, in one of the Geode- 

 phaga, Sericoidiu bembidtoides, K. In one of 

 the palpi in this insect there was a fifth joint, 

 retractile within the fourth. Mr. Kirby sug- 

 gests that since the fifth joint was not apparent 

 in the other palpus, it may perhaps have been 

 a false joint, produced by an effort of nature 

 to repair a mutilated organ, but at the same 

 time observes that if this were the case it is 

 the only instance he has met with in true in- 

 sects of the reproduction of a lost organ. 



The antenna constitute the remaining move- 

 able parts of the head (fig. 369, A). They are 

 occasionally absent in the larva, but never in 

 the perfect state in any insects. They are two 

 jointed organs, attached to the head by a dis- 

 tinct and freely moveable articulation, in some 

 insects near the middle of the front part of the 

 head, but in Hydrous and most Coleoptera 

 on each side immediately anterior to the cor- 

 neae, at the extremity of the epicranial suture, 

 but never, so far as we are aware, in the epi- 

 cranium itself. They are subject to much 

 diversity of form, on which account they have 

 been employed by naturalists as affording cha- 

 racteristic distinctions of different families. 

 They have been divided into several parts, only 

 three of which appear to be generally applica- 

 ble. These are the scapus, (Jig. 371, M 1), pedi- 

 cella (2), and clavola (3).f The scapus, or 

 basial joint, is usually very long, and often the 

 most conspicuous part of the antenna. It is 

 connected with the torulus, or part upon which 

 it moves, by means of a ball and socket arti- 

 culation, beneath the external margin of the 

 clypeus. The second joint, pedicella, in Hy- 

 drous, as in almost every species, is a minute 

 and nearly globular articulation, which allows 

 of the freest motion, and supports the re- 

 maining portion of the antenna, the clavola, 

 which forms the chief part of the organ, and 

 is that which varies most in general structure. 

 When each succeeding joint of the clavola is 

 gradually diminished in size from the base to 

 the apex of the organ, as in the Gryllida, 

 Achetida, and BUitiidec, Jig. 342 and 343, the 

 antenna presents its simplest condition, and is 



* Fauna Boreali-Americana, vol. iv. Insect?, 

 page 15. pi. i. fig. 2. 



t Kirby and Spence, p. 515, et scq. 



