260 EXPEEIMENT STATION RECORD. 



of investig-ntions of this pest by Tucker has been previously noted (E. S. R., 27, 

 p. 562). 



The raspberry horntail (Hartigia abdominalis), E. O. Essig {Mo. Bui. Com. 

 Ilort. Cat., 1 (1912), No. 12, pp. SS9-901, figs. i2).— Reports of damage to rasp- 

 berries and blackberries by " flies " which were afterwards found to be horn- 

 tails, received in February and March, 1912, principally from Placer County, 

 Cal., led to the investigations here reported. 



The insect is generally distributed throughout tlie central and northern foot- 

 hill counties of the State. The principal damage is done to the young and 

 thrifty new growth or canes some time before the appearance of the blossoms. 

 The initial injury is caused by the first hatched larvae wliieh after attaining a 

 length of nearly i in. bore spirally around and down the cane in the cambium 

 layer until the middle pith is reached. The complete girdling of tlie growing 

 part of the shoots causes them to die within a few days, the portion above the 

 spiral being completely destroyed. Upon entering the pith the larva first 

 ascends to the tip, or if the shoot dies before tlie extremity is reached, it 

 retraces its path and continues on down the pith. In spite of the attack the 

 bushes recovered and sent out new shoots just below the spiral made by the 

 larvae and a good crop was produced, tliough many canes were killed outright, 

 thus causing some loss. Canes not affected by horntails failed to throw out 

 these spurs and produced earlier and larger berries in somewhat greater num- 

 bers. 



The eggs are inserted in a slit just beneath the bark of the young canes, 

 usually only one in a cane but in a few cases two have been found. The point 

 of insertion is generally near the second or third leaf axil and within G or 8 

 in. of the tip. At Bowman, Cal., egg laying begins the first of May and con- 

 tinues until after the middle of the month. Upon hatching the larvae remain 

 for a while near the place in which the egg was deposited, feeding upon the 

 surx'ounding tissues, but never disturbing the outer bark before commencing 

 their journey downward. The spirals formed may consist of from 1 to 3 com- 

 plete rings, which may be compact, occupying i in. of the length of the canes, 

 or if loose, occupying more than 1 in. "As soon as the branch is dead the 

 larvse turn and retrace their paths downward, working on the middle pith 

 alone, all of which is digested or converted into frass behind. The length of 

 the burrows varies considerably. In most cases the larvae stop within 1 or 2 

 ft. of the ground for pupation, while in others thej' may continue to the 

 surface of the soil or to the very roots. During this downward path apparently 

 no damage to the cane is done. The larval stage occupies most of the suiumer 

 months, from April to October, though during this period there are many over- 

 lapping broods. The average age for each larva is from 4 to 6 months." The 

 larvae sjjin a thin white silken cocoon or web within the burrow and pupate, 

 the transformation requiring from 1 to 2 months. When fully developed the 

 adult insect gnaws a hole through the side of the cane and escapes. 



While at present a pest only in the higher altitudes of Placer, Amador, and 

 Nevada counties, it has also been reported as occurring in Tehama, Butte, and 

 Sacramento counties, where some damage is being done. Thus far only one 

 native food plant, the wild rose, has been reported. At present the most damage 

 is being done to the raspberry fields in the higher altitudes where such berries 

 are raised to a considerable extent. In many fields in Placer County over 90 

 per cent of all canes were affected. It also works on rose bushes, entirely 

 destroying the year's crop. In Sacramento they were found attacking the 

 canes of blackberries in the same manner as in the raspberries and roses. 

 Loganberries are also among the hosts. 



