BLECHNUM. 



[ 81 1 



BLIGHT. 



tbev are inserted close to the inner mars:ins 

 of the eyes ; basal joint stout and subovate, 

 second and third squarish, larger than any 

 of the follo^^'ing, which are ring-shaped 

 towards the base of the antennae, become 

 square (in the side view) at the middle, and 

 oblong at the apex. Labrum (fig. 1 e, fig. 22, 

 lower part of a) exserted, entire, rountUsh, 

 truncated at the base. Mandibles (fig. 22 b) 

 short, stout, toothed at the tip and on the 

 inner margin; basal ])ortion of the inner 

 margin membranous, forming a little lobe. 

 Maxillee (figs. 1 & 2 ^, 22 c) bilobed; inner 

 lobe (lacinia, fig. 22 c f) dilated and ciliated 

 on the inner margin, acute, curved inwards 

 at the apex so as to form a tooth ; outer 

 lobe (galea, fig. 22 c *) longer, thick, rounded 

 and naked ; maxillary palpi (figs. 1 & 2 ^) 

 elongated, rough with short hairs, -i -jointed, 

 the last joint somewhat hatchet-shaped. 

 Labium (fig. 22 e) elongated, bifid, ^^ith two 

 more slender inner lobes ; labial palpi 

 (fig. 2 k) pubescent, 3-jointed, last joint 

 truncated obhquely. Mentiim (fig. 2 /) short, 

 convex at the base. Eyes (fig, 1 c) kitlney- 

 shaped. 



Thorax semicircular, the base convex ; 

 elytra coriaceous, one overlapping the other 

 and with numerous nerves. Wings large, 

 folded longitudinally, with numerous nerves. 

 Females apterous. Abdomen flat, oval, and 

 terminated by two short, conical, compressed, 

 jointed appendages in both sexes ; besides 

 which, in the male, there are two slender, 

 external, not -jointed appendages or stvles, 

 also an elongated intermediate one. Legs 

 long and compressed; coxfe elongated and 

 stout ; femora stout with a series of spines 

 beneath; tibiae clothed with very strong 

 moveable spines; tarsi 5-jointed, tliree basal 

 joints gradually diminishing in length; claws 

 curved and acute. 



See Insects. 



BiBL. Westwood, Introduction Sfc. ; 

 Kirby, Brit. Entom. i. 12. 



BLECHNUM, Linn. -A genus of Pteri- 



Fio-. 62 



Blechnum.— Pinna with sorus. 



Magnified 



deae (Polypodaeous Ferns) (fig. 62). BI. 

 Spicant, \Yith., is the Hard Fern, called 

 sometimes Bl. boreale, and sometimes Lo- 

 maria Spicant. 



BLIGHT. — This word is used in common 

 language in an exceedingly loose and unde- 

 fined way, being applied to almost every'^ 

 cause of disease in plants, as well as to the 

 diseases themselves, which are variously ex- 

 plamed by agencies of meteorological condi- 

 tions, parasitic plants and insects, operating 

 singly or in combination. Blight is, indeed, 

 ' in the air ' in many cases, since a frequent 

 source of thsease in vegetation is sudden change 

 of temperature or hygroscopic condition of the 

 atmosphere, deranging the processes of eva- 

 poration and respiration in the tender, 

 actively developing portions of the foliage or 

 inflorescence of plants. It is also often ' in 

 the air' in another sense, but much less 

 specially than is commonly supposed : the 

 plagues of parasitic fungi and insects which 

 sometimes cause such devastation, seem un- 

 doubtedly to arise immediately fi-om the 

 transport of the microscopic reproductive 

 bodies, spores and the like, through the air ; 

 but the peculiar atmospheric conditions often 

 observed as accompanying the sudden irrup- 

 tion of large masses of such 'bhghts,' are 

 only collaterally connected with the develoji- 

 ment of these bodies; the warm overcast 

 weather, almost proverbially designated as 

 the cause or the herald of blights, is merely 

 an index of a condition of the atmosphere 

 especially favourable to the rapid multiplica- 

 tion of the Fungi and Insecta which are seen 

 to increase so rapidly at such times, and the 

 germs of these must be already present, 

 through other causes, for the production of 

 the phaenomena under such circumstances. 



Only a few^ of the animal blights need be 

 referred to here, such as the plant-lice, the 

 most familiar form of ' blight ' in cultivated 

 plants (see Aphides), the 'pepper-corn' 

 or 'ear-cockle' of wheat (see Ear-cockle 

 and Anguillula), the wheat-midge (see 



Cecidomya), the tur- 

 nip-fly (see IIaltica), 

 and the species of Cy- 

 7iips and allied genera 

 which produce galls and 

 similar excrescences by 

 the irritation of the ve- 

 getable tissue, resulting 

 from theu- presence. 



Many caterpillars of 

 moths and butterflies 

 are exceedinglv destruc- 



3 diameters. 



G 



