450 INSECTA. 



squamous threads which produces the effect of a sting. The wings are laid 

 horizontally, one over the other, on the body, with little scales. 



The torment we experience from these insects, particularly in the vicinity 

 of low grounds and water, where they are most abundant, is well known. 

 These insects also feed on the nectar of flowers. 



The female deposits her eggs on the surface of the water, and places them 

 side by side in a perpendicular direction ; the entire mass resembles a little 

 bateau floating on that element. Each female lays about three hundred eggs 

 in the course of the year. These insects frequently survive the most intense 

 cold. Their larva; swarm in the green and stagnant waters of ponds and 

 ditches, particularly in spring, the period at which those females lay their eggs 

 who have passed through the winter. They suspend themselves on the surface 

 of the water in order to respire, with their head downwards. These larva; are 

 very lively, swim with considerable velocity, and dive from time to time, but 

 soon return to the surface. After some changes of tegument, they then become 

 nymphs, which still continue to move by means of their tail and its two termi- 

 nal fins. These nymphs also remain on the surface of the water, but in a 

 different position from that of the larva?, their respiratory organs being placed 

 on the thorax ; they consist of two tubular horns. It is in the water also that 

 the perfect insect is developed. Its exuviae form a sort of float or resting 

 place, which keeps it from submersion. All these metamorphoses occur in 

 the space of three or four weeks, and several generations are produced in the 

 course of the year. 



In the other Nemocera, the proboscis is either very short and terminated by 

 two large lips, or in the form of a siphon or rostrum, but directed perpen- 

 dicularly or curved on the pectus. The palpi are bent underneath, or turned 

 up, but, in that case, from one to two joints only. 



Linnfeus comprises them in his genus 



TIPULA, 



Which is now variously divided and subdivided. It includes the various 

 species of the Crane-fiy. 



All the following Diptera, a small number excepted, have their antenna; 

 composed of three joints, the first of which is so short, that it may be excluded 

 from the calculation ; the last is annulated transversely, but without distinct 

 tlivisions. It is frequently accompanied with a seta, usually lateral, and 

 situated on the summit in others, presenting two joints at base, sometimes simple 

 and sometimes silky. The palpi never have more then two joints. 



Some, a few excepted, whose larva? divest themselves of their skin previous 

 to becoming pupae, always have a sucker composed of four or six pieces ; the 

 proboscis, or at least its extremity, that is to say, its lips, is always salient. 

 The palpi, when they exist, are exterior, and inserted near the margin of the 

 oral cavity, close to which arises the sucker. 



The larva 1 , even of those in which the skin forms a cocoon for the pupa 

 (Stratiomys), retain their primitive form. 



This subdivision will comprise three families.- 



