766 



REPORT UNITED STATES GEOLOGICAL SURVEY. 



INSECTS INFESTING THE PEA. 



The Pea-Weevil, Bruchus pisi Liun. (Fig. 33). — Infesting seed-peas, living in the pea 

 its whole life; a rusty black weevil-like beetle, spotted with lighter shades ; a little 

 over a tenth of au inch long. 



The pea-weevil belongs to a small family of beetles called Bruehidce, 

 from Bruchus, the name of the principal genus, of which there are 300 

 species known. They differ from the true weevils in the proboscis being 

 folded on the chest, the antennte being short and straight and inserted 

 in a cavity next to the eyes. The beetles are short and broad, and are 

 noted for their activity and readiness to take flight when disturbed. 

 The pea weevil is oval in form, about an eighth of au inch long, rusty 

 black, with a white spot on the hinder part of the prothorax, and four 

 or five white dots behind the middle of each elytron and a T-shaped 

 white spot on the tip of the abdomen. 



They frequent the pea during and just after the flowering season. 

 Harris states that "after the pea-vines have flowered, and while the pods 

 are young and tender, and thfe peas within them are just beginning to 

 swell, the beetles gather upon them, and deposit their tiny eggs singly 

 in the punctures or wounds which they make upon the surface of the 



pods." Other authors 

 state that with their 

 beak they puncture the 

 base of the flower and 

 lay an egg in the punct- 

 /ure. Kiley tells us in 

 his Third Keport (p. 47) 

 that " the eggs are deep 

 yellow, 0.035 inch long, 

 three times as long as 

 wide, fusiform, pointed 



Pig. 33.— Pea-Weevil, natural size; h, much enlarged; c, ^" front, blunt behind, 

 larva, natural size and enlarged ; d, pupa seen from above, but larger anteriorly 

 natural size and enlarged; g, the beetle coming out of than posteriorly. They 

 the pea (after Curtis) ; /, egg (after Eiley). ^^^^ fastened tO the pod 



by some viscid fluid which dries white and glistens like silk. As the 

 operation of depositing is only occasionally noticed during cloudy 

 weather, we may safely assume that it takes place for the most part by 

 night. If pea-vines are carefully examined in this latitude (Missouri) 

 during the month of June, .the pods will often be found to have from 

 one to fifteen or twenty such eggs upon them, and the black head 

 of the future larva may frequently be noticed through the delicate 

 shell. * * * * 'j'l^e newly-hatched larva is of a deep yellow color 

 with a black head, and it makes a direct cut through the pod into the 

 nearest pea, the hole soon filling up in the pod, and leaving but a mere 

 speck, not so large as a pin-hole, in the pea." The cylindrical, thick, 

 fleshy grub hatches, and perforates the pod, entering the pea, and there 

 lives until it changes to a weevil ; and in stored peas, hibernates within 

 then). Their presence in the pea may be detected by a discoloration 

 made by the larva within, corresponding to a dark spot on the pea. 

 The grub becomes fully grown by the time the pea ripens and dries. It 

 then bores around hole from the hollow in the center of the pea, leaving 

 the hull and generally the germ untouched; hence infested peas will 

 spring up and grow. The grub changes to a pupa within the pea in the 

 autumn, and before the spring casts its skin, becomes a weevil, and 

 ^naws a hole through the pea ; it often does not appear until after the 



