INSECTS 



APTERA 



The insects belonging to this order are small, soft-bodied, wingless creatures with no meta- 

 morphosis, and exhibiting throughout life a very general resemblance to the larval stage of many 

 insects of higher groups. The antennae are often large, and while all possess the three pairs of 

 thoracic legs characteristic of insects in general, some have in addition short limb-like abdominal 

 appendages and a pair of long bristle-like processes at the hind end of the body. Others are 

 provided with a pair of abdominal appendages modified into a springing or leaping apparatus ; many 

 possess on the under side of the first abdominal segment a peculiar structure of doubtful function, 

 known as the ventral tube; and some again have the body thickly clothed with scales, very similar 

 to those of Lepidoptera. 



The order Aptera comprises the two sub-orders Thysanura (bristle-tails) and Collembola (spring- 

 tails). The Thysanura have the abdomen divided into ten segments, some of which the number 

 varies in different genera bear short paired limb-like appendages, while the last segment has a pair 

 of processes or cerci which are generally long, slender, many-jointed, and antenna-like, but in 

 one family form a pair of forceps somewhat like those of earwigs. A single median tail appendage, 

 similar to the cerci, occurs in some forms. 



Of the five recorded British species of Thysanura four have occurred in Nottinghamshire. 

 The best known of these is the common and active little ' silver fish ' (Lephma sacckarina), 

 found commonly in kitchens and bakehouses in Nottingham and elsewhere. Lephma (or Thermobia) 

 domestica has recently (November, 1 904) been sent to me from West Bridgford, Nottingham, where 

 it occurs in abundance among cinders under fire-grates in a dwelling-house. The curious Campodea 

 stapbylinus, a tiny white fragile insect suggesting a minute Myriapod in appearance and movements, 

 is found very frequently under stones and logs and among damp loose soil in gardens and fields 

 throughout the county. Mach'llis polypoda is common under stones in quarries throughout the whole 

 of the Magnesian Limestone district. The remaining British species, Machilh marittma, is confined 

 to the coast, where it occurs under stones at and above high-water mark. 



The Collembola have only six abdominal segments, the first of these bearing a ventral tube or 

 papilla from which in some species a pair of long delicate tubes or vesicles can be protruded. The 

 function of this ventral tube is far from being satisfactorily settled. It has been suggested that it 

 may assist the insect to adhere to smooth vertical surfaces, or may be a respiratory organ. The 

 'spring' is situated on the under side of the fourth or fifth segment of the abdomen, and consists of 

 a basal unpaired portion and two free limbs. When not in use the spring lies parallel with the 

 body, with the limbs or prongs pointing forward, and, in some genera at least, is kept in place by 

 a ' catch ' situated on the third abdominal segment. When the catch is removed the elastic spring 

 suddenly extends, so that the limbs now point backward, and the insect is thus shot into the air. 

 Besides this mode of progression by successive rapid leaps, most of the Collembola can run actively. 



In some springtails the body is clothed with hairs, in others with flattened scales. The colour 

 varies considerably, some species being pure white, others black, while various bright often metallic 

 tints occur, and some species are beautifully variegated. They occur abundantly under bark, 

 rotten wood, stones, amongst moss and foliage, in damp earth, etc. A few inhabit the surface of 

 stagnant water, and one species at least is confined to the sea-shore. Their food appears to consist 

 chiefly of decaying vegetable matter, but several species have recently attracted notice by their injuries 

 to the roots and other parts of cultivated plants. Unlike the Thysanura, the Collembola are not 

 at all intolerant of cold, and may be collected throughout the winter. Several species indeed occur 

 in Spitsbergen, in Franz Josef Land, and on the Antarctic continent. 



Extensive materials for a list of Nottinghamshire Collembola exist in the writer's collection, 

 but as they have not yet been worked out no detailed account of them can be given here. The 

 following species have, however, been identified by Professor G. H. Carpenter in material submitted 

 to him. 



1 The nomenclature and arrangement adopted for the orders of insects are those of Dr. Sharp in the 

 Camb. Nat. Hist. 



79 



