CLASS CKUSTACEA. 



OHDER B RACHYURA. SHORT-TAILS. 



145 



ORDER IX. HOMOPTEROUS INSECTS. 



ILLUSTRATIVE EXAMPLES. 



LYSTRA. Head transverse, and not prolonged into a horn ; body long ; 

 elytra not enlarged behind as in the genus Flatta, nor narrowed into a point 

 as in Icyus. 



The type, L. lunata, Fabricius, is found in South America. 



Illustration : Lystra lannginosa. 



FLATA. Antennae with three distinct joints, the second the largest, 

 cylindrical, ovoid or nearly globular, inserted immediately under the eyes ; 

 head generally transverse, and not prolonged, or at least only forming a blunt 

 point ; ocelli two ; wings very broad, and the elytra applied one against 

 the other by their hinder edge. 



The females envelope their eggs within a white cottony substance, which 

 is placed at the end of the abdomen. 



The genus has been divided into two sections, according to the colour of 

 their wings : I. Wings variegated with colours, and II. Wings transparent. 



Illustration : Plata allxi. 



DELPHAX. Antennae inserted in a niche under the eyes, a little longer 

 than the head, the first joint shorter than the second. 



The wings of this genus are usually very short ; and the habits of the 

 species are most probably very similar to the other Cicada. 



Illustrations : Delphax pellucidus, D. dorsatus. 



THRIPS. Antennae filiform, almost setaceous, eight-jointed, nearly as 

 long as the head and thorax ; beak very small, scarcely apparent, consisting 

 of a sheath, formed by a pair of three-jointed valves, between which is the 

 sucker, with a pair of very short filiform, three-jointed palpi ; body lengthy, 

 terminating behind in a kind of tail ; wing-cases and wings nearly similar, 

 linear, horizontal, and ciliated on their edges ; tarsi very short, two-jointed, 

 of which the second is vesicular, and not armed with clawlets. 



These insects are the smallest of the Aphidian family, and some are 

 scarcely visible. They are natives of Europe, and live upon flowers and the 

 bark of plants. 



Illustration : Thrips caeruleocdlis. 



OKDEK X. STREPSITEROUS INSECTS. 



THE Strepsiterous, or Twisted-winged, Order of insects was established 

 by Kirby, and consisted of the genera Stylops and Xenos. In these genera 

 the soft coriaceous elytra are placed very near the head, not on the back, 

 however, but attached to the coxa? of the anterior pair of legs ; they are 

 widely separate from each other, and never come in contact, but recede 

 from the body, then curve towards, and a second time diverge from it. 

 Lamarck and Latreille, however, deny tliat the elytra, so called by Kirby, 

 are other than scales, because elytra never have such attachment, which 

 remarkable variation is the precise reason why Kirby forms his new Order. 

 Lamarck, however, does not consider them entitled to the rank of a distinct 

 Order, but makes them a section of his Dipterous Order. 



ILLUSTRATIVE EXAMPLES. 



STYLOPS. Antennae biarticulate at the base, and sending out two branches, 

 long, compressed, unequal, of which the upper is triarticulate. 



This genus is distinguished from Xenos by the unequal length of the 

 antennae, and by the jointing of the upper one. 



Illustrations : Stylops melitae, S. Kirtti, S. DaKi. 



XENOS. Antennae three-jointed at the base, and thence cleft to their tip 

 into two branches of equal length, slender, semicylindrical, and jointless ; 

 eyes pedunculate and cellulous ; abdomen projecting, horny, with a fleshy 

 vent. 



This curious genus, of which the larva is parasitic, and lives in the belly 

 of the Wasps called Polystes, was discovered by Rossi in the French species, 

 and subsequently by Peck, in P. Fuscata, an American Wasp, who says, 

 that the abdomen of such Wasps is so distorted by this larva, that he had no 

 difficulty in knowing them when on the wing. Rossi observes that it is 

 the fourth abdominal segment from which the Xenos in its pupa state 

 usually emerges sometimes one, often two, and occasionally three, from 

 the same Wasp ; it emerges in its imago state in the month of August or 

 in September. 



Illustration : Xenos vesparum. 



CLASS VII. CRUSTACEA. 



THE covering of this Class of Articulated Animals is less solid than the envelopes of the majority of Testaceous Molluscs ; but their 

 skin is much tougher than the skin of the Naked Molluscs. In their respiratory, circulating, and locomotive organs they are 

 distinguished from three other Classes. In the arrangement of this Class, almost every writer of note has adopted views distinct 

 from the others ; hence the great dissimilarity of classification which exist in the several works published on those interesting 

 animals. In March, 1830, Milne Edwards read before the Royal Academy of Sciences a paper, in which the construction of the 

 oral organs is made the foundation of their division into two sections : the first including those of which the mouth is not furnished 

 with any special organs of mastication ; and the second composed of such as have proper masticating organs, viz., a pair of mandibles 

 and one or more pairs of maxillaries or jaws. Subsequently, however, in his excellent work, Histoire Naturelle des Crustaces, 

 1834, Edwards found it necessary to form a third section for the Xyphosuriau Crustaceans, which he had previously included in 

 his first section, to which they had little resemblance, and indeed are more nearly allied to the second, although sufficiently distinct 

 from it also to justify their formation into a distinct section. He therefore arranges the Crustaceans in the three Classes : 1. Suckers ; 

 2. Xyphosures ; 3. Masticators ; and these, with the exception of the second, he divides into several Orders : the Class Suckers, 

 including the Arane form, Lern form, and Syphonostemous Orders, and the Class Masticators, comprising the Entomostracous, 

 Branchiopodous, Trilobites (fossil), and EdrioptJialmous legions, with their several Orders, all of which are devoid of true branchiae 

 or gills, together with the Podopthalmous legion, and its Orders, which have perfect branchiae, and are the most highly developed 

 of the whole Class. 



Ix Milne Edwards' classification of the Crustacean families, we find 

 placed in his PODOPTHALMOUS legion the short-tails (Brachyura), the long- 

 tails (Macroura), and the > footed^mouths (Stomapoda) ; his EDRIOPTHALMOUS 

 legions contain, among others, those with equal legs (Isopoda) ; and his 

 BRACHIOPODA are crustaceans destitute of true branchiae, but having their 

 thoracle extremities so formed as to serve the purposes of respiration. 



The first Order of Crustaceans, according to Latreille, is the Decapoda, 

 the situation of whose gills, and the number of legs, form their essential 

 character. 



This Order is formed of the genus Cancer of Linnaeus, excepting some 

 species with naked gills, and of the classes Kleistagnatha and Exocthnatha 

 of Fabricius, adding the genera Limtdus, SqtciUa, and Gammarus ; and it is 



