Observations on Insects affecting the Turnip Crops. 53 



the pairing of the sexes. The Aphides generally deposit their 

 eggs, which are hard, and like parchment, in the most secure 

 places, under the buds, in the forks of branches of trees, &c., 

 and sometimes, it appears, upon the leaves.* 



The young are furnished with horns and legs, like their pa- 

 rents, but they are generally narrower in proportion, and often of 

 a different colour. Like most insects in their growing state, they 

 change their skins several times, which are left sticking to the 

 plants on which they live ; and they are never deprived, from 

 their birth to their adult state, of the power of locomotion, as the 

 turnip-beetles and turnip-saw-flies are, which lie quiescent in 

 their pupa state. The Aphides belong also to an order which 

 we have not before noticed, called Homoptera, but it formed a 

 section only of Linnaeus's order Hemipt era : the family is named 

 Aphidid^, containing, amongst other groups, an extensive genus 

 called Aphis. 



This genus f has two horns (fig. 11), considerably longer than 

 the body, often as long as the wings, naked and tapermg like 

 bristles, inserted in front of the face, composed of seven joints, 

 of which the two first are short and oblong, the following long, 

 especially the third. Rostrum bent under the breast, short, and 

 four- jointed, longest in the females (fig. 9/i). Eyes globose and 

 lateral (9 i) ; ocelli, or simple eyes, three, very remote (9 A:). 

 Collar of thorax very long in the males. Abdomen ovate-conical 

 in the males, with two tubes on the fifth segment. Wings four, 

 transparent, deflexed in repose ; superior twice as long as the 

 body, ample, with several nervures, the furcate apical cells short : 

 inferior wings much smaller, with a nervure forming three rays. 

 Females generally apterous ; the bodies stouter. Legs six 

 (fig. 12), long and slender, especially the hinder pair : thighs 

 long (12 Z); shanks longer (m) ; feet short, composed of two 

 joints, the first scarcely visible (n), terminated by two curved 

 acute claws (o). 



The different species already alluded to I will now proceed to 

 describe : — 



1. Aphis Rapae, Curtis I — the Turnip-leaf plant-louse. 



Male — ochraceous; horns moderately long, setaceous, fuscous, 

 two first joints black, third ochraceous at the base : head blackish, 

 collar ochraceous and brown, disc of thorax shining black ; abdo- 

 men greenish, the spiracles or breathing pores brown : tubes long, 

 slender, ochraceous at the tip ; the apical process of the body 



* Mr. W. Curtis saw several small irregular groups of eggs of an Aphis 

 which were deposited on both sides of the leaves of some Auricula plants, 

 in November. 



t Curtis's British Entomology, fol. and pi. 577. 



$ Curtis's Guide to an Arrangement of Brit. Ins., Genus 1047, 18 b. 



